PRELIMINARY STUDY FOR THE IDENTIFICATION …assets.panda.org/downloads/wwfaltenativestothewater...1 World Wide Fund for Nature PRELIMINARY STUDY FOR THE IDENTIFICATION OF VALID ALTERNATIVES

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World Wide Fund for Nature

PRELIMINARY STUDY FOR THEIDENTIFICATION OF VALID ALTERNATIVESTO THE WATER RETENTION BASINS TO BECARRIED OUT IN THE MIDDLE REACHESOF THE TAGLIAMENTO RIVER

VOL. I Hydraulic, socio-economic and environmental aspects

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Contribution:

Hydraulic analysisProf. Eng. Ezio Todini, University of Bologna, Faculty of Engineering

Socio-economic analysisDr. Roberto Chiesa, agri-economist, project evaluatorDr. Livio Comuzzi, town planner

Environmental analysisDr. Andrea Marin, doctor of Natural Sciences

Co-ordinationDr. Nicoletta Toniutti – WWF Italy

SupervisionDr. Andrea Agapito Ludovici – WWF Italy

TranslationDr. Olivia Bisegna and Dr. Elisabetta De Martin

Acknowledgements

For the support offered in different ways to the present work we would like to express our thanks to:Prof. Giuliano Cannata, Mayor Paolo Menis and the Municipality of San Daniele del Friuli, Prof.Klement Tockner of the Swiss Federal Institute of Environmental Science and Technology (EAWAG-ETH), Michela Ostan, Dr. Peter Jürging and Dr. Klaus Lintzmeyer of Verein zum Schutz der Bergwelt,Eng. Sara Poluzzi, Eng. MarcoVescia, the WWF European Alpine Programme (WWF Austria, WWFGermany, WWF Italy, WWF Switzerland) and the WWF European Policy Office (Brussels).

We would also like to thank the over 700 scientists, researchers and scholars, 8000 European citizensand dozens non-governmental Organisations and study centres all over Europe that signed theinternational WWF petition for the protection of the Tagliamento River.

Cover photo: Bar-braided and island-braided reaches of the Tagliamento River.(Photo by Toni Vorauer, WWF Austria)

1st Edition: October 2003

February 2004(Edition revised and corrected)

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LIST OF CONTENTS

Introduction page 4

Reference Context• New European water-related directive page 6• The Tagliamento issue page 8• The Tagliamento River and its territory page 9• Protection objectives and possible actions page 11• The European experience page 12• Specific Objectives and types of actions page 14

Alternative proposal for the abatement of the flood peak• The floodplain between Pinzano and Dignano page 16• Applied methodology page 17• Analysis results page 19• The alternative proposal page 21• Critical issues analysis page 26• Hydraulic analysis conclusions page 27

Ecological aspects of the riverine corridor• Ecological framework page 29• Conservation areas in the high course of the Tagliamento river page 31• Conservation areas in the middle course of the Tagliamento river page 31• Ecology of the middle reach of the Tagliamento river page 32• Conservation areas in the low course of the Tagliamento river page 36• Final considerations page 37

Economical and community impact analysis• Analysis set up page 39• Evaluation methods page 39• Status quo and alternative projects page 40• Identification of concerned areas page 43• Description of scenarios and definition of evaluation criteria page 44• Evaluation of costs and benefits page 48• Identification of stakeholders page 51• Summary evaluation page 57• Conclusions of the economical and community impact analysis page 59

Towards an integrated management plan of the Tagliamento basin page 62

Annex• Comparison of the two hydraulic proposals page 63• Towards an action plan for the Tagliamento River page 64• Renaturalisation page 69

References page 71

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INTRODUCTION

The Tagliamento is the most important river in the Friuli Venezia Giulia region, an extraordinaryelement of the Friulian landscape, a territory characterised by a great bio-diversity of wild flora andfauna, a natural, open-air laboratory where river ecology researches are conducted by scholars from allover the world, but it is also much more. It is also a feature and a basic element of our cultural heritage,intended both as a succession of cultures and human situations, developed around and together withthe river, and as natural history developed according to the various geological eras.

Therefore, whoever understands its “existence value” cannot, but recognise that it is an extremelyimportant living system we are an integral part of. The WWF, fully aware of everyone’s responsibilitytowards the river, felt the need to undertake a number of initiatives aimed at guaranteeing a sustainablefuture for the Tagliamento and its communities.

Based on the above assumption, the WWF initiated a multiple-stage process, involving the EuropeanCommission, the International Scientific Community, the local municipalities (with the presentation ofdossiers and information activities), as well as the WWF European Alpine Programme, which identifiedthe Tagliamento River as one of the rarest European environments to pass on to the futuregenerations. Moreover, a petition for the safeguard of the river, involving thousands of Europeancitizens as well as dozens of Non-Governmental Organisations and scientific research centres, wasmade thanks to the International Scientific Community.

The study presented herewith is an integral part of this process and arose from the wish to help identifythe best solution to an important and unavoidable problem – such as the safety of the riverine peopleexposed to the risk of floods – but also to embark on a shared, transparent and innovative programmeaimed at defining an integrated basin plan for the protection and preservation, over time, of theenvironmental and socio-economic values of the territory crossed by the river.

The working methods used required a multidisciplinary approach with the involvement of specialists inthe field, based on the analysis of currently available data, an in-depth study of the most advancedscientific acquirements, a comparison with other European and international experiences, as well as oninspections made along the river corridor.

A first important result was indeed achieved: the identification of sustainable alternatives to the waterretention basins set out in the “Abridged plan for the hydraulic safety of the middle and lower reachesof the Tagliamento River” issued by the Basin Authority for the North Adriatic Rivers (Venice) to becarried out in the Site of Community Importance (SCI) called “Greto del Tagliamento” (Shingle of theTagliamento River).

According to the proposal presented herewith, the WWF believes that it is possible to achieve anintegrated basin management plan that, with the qualified contribution of technicians and scientists aswell as the shared and active involvement of all parties concerned, would safeguard, preserve andenhance the value of an important area of the Friulian territory for future generations.

This is what European scientists and scholars currently recommend and advocate, also in line with therequirements of the new and advanced European Directive 2000/60 EC of 23 October 2000, whichsets out the framework for a water-related community action.

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Fig 1 View of the Tagliamento floodplain between the towns of Pinzano and Dignano. In this area, which corresponds toone of the Site of Community Importance (SCI) called “Greto del Tagliamento” (Shingle of the Tagliamento River), the“Abridged plan for the hydraulic safety of the middle and lower reaches of the Tagliamento River” envisaged theconstruction of three 30-million m3 water retention basins in order to reduce the flood peak from 4600 m3/s to 4000 m3/s.Here, the riverbed is embanked between two steep escarpments of fluvial erosion, spaced 3 km apart, on average (Photo byArno Mohl WWF Austria).

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REFERENCE CONTEXT

NEW EUROPEAN WATER-RELATED DIRECTIVE

Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 sets out theframework for a water-related community action and represents a reliable and binding reference pointfor the management of all water bodies.

The Directive, which must be implemented by Member States by 22 December 2003, requires them toprevent further water bodies deterioration, thus improving and re-naturalising the aquatic and terrestrialecosystems, which depend on the presence of water. The key objective is, for most surface water, toachieve “good status” by 2015, where the latter will be assessed by reference to a set of biological,hydro-morphological and chemical-physical parameters and indicators.

In order to achieve the above objective, Member States should start taking a series of important steps,including:

By 2003:Identification of the catchment basins and assignment to the relevant River Districts;identification of the relevant Authorities;

By 2004: Carrying out of analyses in order to define the characteristics of the various river districts andthe environmental impact of human activities, the economics of the water usage and setting-up of a register of all protected areas situated within the river districts;

By 2006: Inter-calibration of the water ecological status classification systems according to parameterscommonly used by the European Community;Implementation of network systems to monitor the status of surface and groundwater as wellas water of protected areas;

By 2009: Definition of a programme of measures, which taking into account the results of the analysispermits the achievement of the environmental objectives of the Directive; drafting ofcatchment basin management plans;

By 2010:Definition of water pricing policies enhancing the sustainability of water resources, by applyingthe full cost recovery principle and including environmental and resource costs;

By 2012:Implementation of a programme of basic and additional measures to be applied to theidentified River Districts;

By 2015:Implementation of all necessary measures required to avoid pollution of all surface andgroundwater bodies, as well as to prevent, completely or partly, hazardous substances frompolluting groundwater.

It is the first time that a European Directive is concerned with the chemical-physical condition of waterbodies as well as their ecological efficiency, which needs, not only to be maintained at its current level,but also improved.

Member States are, therefore, not only asked to define the features of the river districts, includingrelevant river basins, to analyse the environmental impact of human activities and the economics ofwater usage, to monitor surface and groundwater as well as water of protected areas, but also to takethe necessary measures to prevent the deterioration of all surface and groundwater bodies.

Both the precautionary principle, ruled by Article no.1, which among the various goals of the directiveincludes the prevention of any further deterioration of aquatic ecosystems, and the principle that “thepolluter pays” underpin the sustainability of water usage and its long-term protection.

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One of the goals of the Directive is the development of a framework to protect inland surface water,transition water, coastal water and groundwater, which would not only “promote the sustainable usageof water based on a long-term protection of water resources available”, but also “mitigate the effects offloods and droughts”.

The new trend, therefore, aims at enhancing the value of the various functions of water, as an asset,and recognising the coexistence of different needs: the protection of people against safety and healthrisks (social aspect), the efficient access to resources by people and productive activities (economicalaspect), the conservation of resources as well as the preservation of their ecological functions(environmental aspect and cross-generational fairness).

The transparency as well as the effective and active involvement of all parties concerned underlie thisnew trend, as ruled by Article no.14: “Member States shall encourage the active involvement of allinterested parties in the implementation of this Directive, in particular in the production, review andupdating of the river basin management plans...”

Therefore, a “sustainable” approach to flood control must evaluate the complexity of objectives andinterests and take that into account in trying to find out valid solutions, by setting out policies and bydrafting plans, schedules and projects.Sustainable flood management requires the development of a participatory approach to disasterplanning and decision-making by involving all private and public bodies operating on the territory,where the involvement of all parties concerned is not just a requirement to be complied with, but oneof the key factors of the process.

This work which focuses on the Tagliamento River and wishes to identify those actions which bettermeet the safety needs of the population, from the point of view of economic efficiency and renewed“coexistence” with the river and its effects, falls under the above “trend” towards sustainability basedon the spirit of the new community regulation.

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THE TAGLIAMENTO ISSUE

The Tagliamento is considered a torrential river1 due to its highly irregular flow. The riverbed itself isthe result of this fluvial dynamics, which have “marked” the spaces within which the river currentlyflows under normal conditions. For the last dozens of years, interest for the river and its riverbed hasincreased due to the acknowledgement of their intrinsic environmental value as well as to the heavy“artificialisation” of other European rivers with similar features. As a consequence, the river has been,for many years, the object of advanced studies by important international research centres2.

Fig.2 Catchment basin of the Tagliamento River

Floods are sporadic events and not exceptional phenomena, since they are natural effects of riverbehaviour. Flood dynamics (strength, frequency) and its effects (affected areas and resulting damages)have been especially influenced by the hydraulic works carried out in the last century and by the landmanagement of the catchment basin area, the river area and those external areas, which aremorphologically more exposed. The abandonment of agro-forestry-pastoral activities, the reducedcatchment capacity of the mountain basins, the use of floodplains for production purposes and the

1 - Spaliviero M. (2002), Historic fluvial development of the Alpine-foreland Tagliamento River, Italy and consequences for floodplain management,Geomorphology 1277 (2002), 1-17- Arscott, D. B., K. Tockner & J. V. Ward (2000): Aquatic habitat diversity along the corridor of an Alpine floodplain river (Tagliamento River, Italy).Archiv für Hydrobiologie 149: 679-704.- Tockner, K., J.V. Ward, D.B. Arscott, P.J. Edwards, J. Kollmann, A.M. Gurnell, G.E. Petts and B. Maiolini. (2003). The Tagliamento River: A modelecosystem for Alpine gravel-bed rivers. Aquatic Sci.65: 239-2532 Among these we would like to mention the Swiss Federal Institute of Environmental Science and Technology, EAWAG/ETH, which has been co-ordinating, for years, teams of scientists from all over the world.

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increase in their value due to a more intensive use of risk-prone areas caused changes in the locationand degree of danger.The Alpine and middle reaches of the river have remained decidedly “natural”, despite numerousactions that contributed to modify their water dynamics, thereby increasing the hydraulic risk, especiallyin the lower stretch of the river.A study conducted by the Friuli-Venezia Giulia region, dated 19793, tells us that: “It is true that, sinceancient times, human kind has carried out works for the channelization of streams, rivers, hydraulic land reclamation,landslide stabilization as well as protection against sea storms, which have partly contained the risk. But it is also truethat, in the last few years, in addition to sensible initiatives, other headlong, overhasty and incautious activities have beencarried out such as floodplain reclamation, narrowing of riverbeds, illegal dumping of waste and anomalous collection ofstony material from river, modification of riverbeds and waterways, abstraction of fluvial waters, drainage of humid areasand, finally, destruction of natural vegetation or modification of the original morphology even on potentially dangerous oravalanche-prone slopes.”Asphalt works, roads, viaducts, urbanisation and riverbed works reduce outflow times – as furtherconfirmed by a more recent study4 - and, at the same time, increase flood peak discharges of theriverbed. This means ever-increasing amounts of water due to the reduced average permeability of thebasins and shorter and shorter flood runoff travel time. During the flood of 4 November 1966, inLatisana – a town situated along the lower river course, which, in this stretch, has become almost acanal – water level exceeded m.4.90, whereas documentation evidence shows that, in Venzone5, over 25years, from 1940 to 1966, the maximum water levels had increased from 80 cm to 1 m.The hydraulic safety of the Tagliamento is a problem involving all the communities living onthe territory crossed by the river, therefore, all parties concerned should endeavour to find asolution.

THE TAGLIAMENTO RIVER AND ITS TERRITORY

The localities found in the municipalities situated within the catchment basin of the Tagliamento arestill the same as they were at the beginning of the nineteenth century, when the territory was recordedin the Napoleonic land register.By comparing the present regional technical map with the military maps of 1891 and 19606, whichshow the course of the Tagliamento from Pinzano to the sea and its riparian strips, it may be noticedthat the town planning scheme adopted in the last ten years confirmed and reinforced the settlementdistribution as it had been structured in previous ages7.Since ancient times, Latisana and San Michele have developed around the course of the Tagliamento,whereas all places downstream of Latisana appear to be situated along its flow, as if they were“offering” themselves to the river. Obviously, at that time, the river behaviour did not affect thesurvival of the built-up area. Rosa (a village in the municipality of San Vito al Tagliamento), which leftbehind its parish church on the opposite bank of the river, is the only case where a built-up area wasactually moved due to flood safety reasons.Since the early Seventies, the development of urban areas in Latisana and its neighbouringmunicipalities has been carried out paying little attention to the river and giving hydraulic safety8 forgranted. At that time, the Municipality used to plan according to the constraints of the Piano

3 Stefanini S., Gerdol S. Stefanelli A. 1979, Studio per la definizione dei pericolo naturali nella Regione Friuli Venezia Giulia (alluvioni, mareggiate, frane evalanghe), Regione Autonoma Friuli Venezia Giulia Assessorato dell’Agricoltura, Foreste, Economia montana, Direzione regionale delle Foreste.4 Altan M.G.B., Castellarin B., Fantin E., Foramitti R., Romanin F., Turoldo D.M., 1990, Le alluvioni del Tagliamento a La tisana e nei comuni della bassafriulana, Ediz. “La Bassa”-collana/125 Small town situated in the upper catchment (see fig.2)6 Or with the Austro-Hungarian military map preserved in the Kriegsarchiv in Vienna.7 Some towns and their adjacent areas have always coexisted with the overflowing of the Tagliamento, which has been the reason for their existence sincetime immemorial. Initially, Latisana was as a wading point in the river, then it developed as a merchant harbour and eventually discontinued these activitiesdue to the frequent flooding of the Tagliamento (approximately in the sixteenth century).8 A slightly lax town planning may be ascribed to the town of Latisana for permitting types of urbanisation, which assumed that the river was safe. This,however, was only applied to those parts of the town outside the historical centre, where the possibility of making arrangements to face a flood event isclearly reduced.

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Urbanistico Regionale Generale - PURG (General Regional Urban Plan) and the geological norms,which were applied, based on regional superordinated viewpoints.As a matter of fact, in the case of Latisana, town planning and river safety measures follow their ownpaths, which intersect only marginally and seldom in a satisfactory manner. The regional geologicalopinions concerning the Piani Regolatori Generali Comunali – PRGC (General Town planningSchemes) have never voiced the hypothesis that the dikes could collapse or fail in controlling thefloods. Thus, the town of Latisana developed, coherently with this misleading certainty, by associatingsafety with the positive geological-hydraulic judgment of the Piani Regolatori Generali Comunali -PRGC (General Town Planning Scheme).

Fig. 3 PRGC, variation no. 30 - Municipality of Latisana (Latisana – Latisanotta zoning)

These observations should not be read as a trial of past events, instead they simply highlight theevolution of the relationship between the river and the town over the last dozens of years (despite theflood of 1966), based on the symmetric assumption that Latisana can develop because the river is safe,i.e. the river must be safe, for Latisana to develop.According to this point of view, the settled territory and the river are considered as two separateelements, which barely communicate with each other, as highlighted by the town planning schemesadopted by the majority of the riparian towns.Floods are tackled as “emergency events”, therefore solutions based on important and precise projects,such as embankments, artificial schemes, dikes, channelizations, re-calibrations, are unavoidable.However, the hydraulic constructions in place provide an excessive trust in the river, as it is believedthat the latter can be dominated at all times thanks to the recent developments in engineeringtechniques and materials used.Furthermore, in recent years, the situation has worsened since the population has demanded highersafety levels than the ones, which hydraulic engineering techniques can guarantee without causing aripple effect in other areas.In fact, the reclamation of the floodplains in the Spilimbergo area, for agricultural purposes, was carriedout based on the above-mentioned belief that the river can be controlled. The river is viewed either asan accident to be tolerated or as a resource to be exploited, often disregarding its naturalness, whichcharacterizes not only the river corridor which conveys the flood, but also the whole basin, as well asthe fact that the river is an integral part of the territory it crosses.No particularly significant actions are taken to check the catchment basin and to integrate the river withthe territory. On the other hand, whilst any direct action on the ability to control the discharges can beimmediately perceived and carried out within a defined timeframe, the same does not happen with theimplementation of policies aimed at restoring (or, at least, preventing its degeneration) the basin soil

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water retention capacity and the natural behaviour of its numerous effluents (the Tagliamento River has236 tributaries, including both direct and indirect)9.In short, in the light of future actions, three elements stand out with regard to the interrelationship withthe Tagliamento:

1. The indifference of the municipalities and the population alike and their biased groundless trustin settling in a flood-prone territory, because more importance is attributed to the quality ofservice, the historic sense of belonging and the reluctance to relocate compared with the floodrisk;

2. The irrational use of the historic riverbed for economical exploitation purposes;3. The difficulty encountered by public institutions in tackling any issue in a complete and

integrated way. The evidence of the facts proves that the dialogue among the various State andRegional bodies as well as Municipalities becomes difficult and quite often comes to a deadlockdue to incompatible choices of opposite interests often examined in watertight compartment10.

PROTECTION OBJECTIVES AND POSSIBLE ACTIONS

By objective we mean a situation, which is hoped to be achieved in the future, in terms of both qualityand services of whatever nature. The correct definition of objectives is fundamental to be able to guideany action. Based on the current technical and administrative setting, objectives are often considered asimplicit and the attention is mostly focused on “what to do”, on the works and any related financial andadministrative issues. Instead, objectives deserve to be clearly defined and shared by the population aswell as the local government involved.Assigning priorities to objectives has significant practical consequences. With regard to the decisionmaking process, it allows a more transparent and respectful comparison of the various interests of thedifferent communities, both among the communities themselves and with external parties. With regardto technical choices, a clear definition of the situation to be achieved offers the opportunity to considerseveral action strategies as potentially applicable and it stimulates the development of new alternatives.In brief, the clear definition of objectives guarantees greater effectiveness; it prevents focusing attentionon a single result and widens the choice of possible actions.In the case under examination, if the primary objective is the safety of the population and of theeconomic values located in a potentially flood-prone area, the meaning of safety must be clearly setout and it must be connected with the other objectives emerged in the debate, which has characterisedrecent years. Different social bodies and communities of the area affected by the rivercourse areresponsible for values of different nature, which all deserve equal attention. These interests, which areoften viewed as conflicting, should be treated as concurrent, that is existing within the same decision-making field.

For this reason, before analysing the technical proposals, it would be worthwhile examining themeaning of “safety”, as the main action objective.The concept of “absolute safety”11 could be defined as the elimination of all risks due to extremeevents. This objective does not seem realistic, both from a technical, economical or environmentalpoint of view. Extreme events are, by nature, unpredictable and their magnitude is unknown. Historicalinformation is too limited and uncertain to provide reliable indications. Climatic evolution increases 9 In order to provide an order of magnitude, each millimetre of water withheld in excess on the entire basin corresponds to 2,500,000 m3 less water feedingthe Tagliamento flood. However, it is important to recognize that it is not only due to the modifications made to the basin, especially in mountainous areas,as floods took place even when the territory was under careful protection (for economic reasons linked to self-consumption) (1920, 1965, 1966).10 Even science, with regard to a rather uncertain issue like the assessment of floods in torrential regime with heavy sediment transport, has difficulty inproviding analyses as well as satisfactory and shared solutions, suffice it to recall the various results achieved by research commissions and the differentsafety measures recommended for the Tagliamento.11 At sitting no.29 of 2 August 2001, the Public Works Committee of the Chamber of Deputies, in one of its guideline acts concerning the Governmentaction on hydro-geological matters, quotes: «the illusion – often fuelled by the formulation of projects which claimed to be conclusive – to be able toachieve absolute safety from the hydro-geological risk with massive works, to «dominate» every wild watercourse and every natural phenomenon must beavoided".

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uncertainty, with changes in local pluviometry, which have not yet been defined. Therefore, theobjective of attempting to prevent damages due to extreme events is incorrect and probably alsounrealistic.The concept of safety is often interpreted as containing the risk of floods occurring in a certain periodof time; at present, the idea is that floods may be expected on average “once every one hundred years”.This approach is an accepted compromise between economical and technical requirements. However,negative consequences are likely to follow. Often, paying attention only to this aspect of the event leadsto very partial and concentrated solutions, which expose the community to the risk that defence worksmight not operate properly and, sometimes, increase the risks run by the population when events of agreater magnitude occur. In addition, the feeling of safety given by hydraulic protection measures leadscommunities to underestimate these risks, and makes individuals less willing to adopt other preventivemeasures and develop any form of defence.Periodic risk parameters remain important reference points for the definition of the action plan,however, they should be considered in the light of a broader framework of objectives, which must benow based on the need to learn how to live with the river and its effects with a new awareness,and to be able to manage rather than contrast the river dynamics.Probably, the objective to be achieved should no longer be the containment of the flood event,but rather the guarantee of safety conditions for each part of society and the territory. By sodoing, values such as human life and place identity which cannot be negotiated and must be whollyprotected12, can be distinguished from others, such as economic assets, which must be evaluated andcorrelated with other public interest values.It would be useful to identify the acceptable risk, such as the situation where non-negotiable values areguaranteed, social and environmental impact minimised and the best compromise achieved between theavoided economical damage and the related defence action costs.

THE EUROPEAN EXPERIENCE

In all of Europe, in the continental region in particular, a change of paradigm is taking place with regardto the management of basins and the defence from flood events.This change stems from the acknowledgement of three factors:a) an impossible absolute defence;b) the need for a wide and fair sharing of responsibilities and allocation of charges;c) the need to contain the negative effects of actions taken to modify the natural dynamics of the

watercourses.

Under the new framework, social and environmental objectives become just as important as theprotection objectives.Accepting the above statements involves the development of policies and operational tools aimed at:a) considering defence as containment rather than elimination of risk, to be achieved by combining a

number of different actions;b) act on the entire basin and not just on the watercourse or one of its stretches and perceive the river

as an element closely related to the environment and human communities;c) envisage diverse and gradual actions (no miraculous solutions exist);d) maintenance and monitoring should play an important role;e) involving and coordinating all the institutions acting on the concerned territory and its citizens, also

through mutual assistance actions13 and insurance schemes;

12 These values are still poorly safeguarded, taking into account transport policies, safety at the workplace, protection of environment and territory.13 Mutual assistance actions are forms of cooperation between different bodies or institutions according to which, instead of receiving/making payment forthe assistance service rendered/received, the parties involved accept to sign a “mutual aid” agreement in case of need or collaboration due to a commonthreat.

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f) avoiding to interfere, as far as possible, with the natural dynamics of the watercourses whencarrying out hydraulic management and territorial planning actions;

g) being prepared to face a case of emergency.

Three aspects of the European experience deserve to be briefly examined. The first relates to thedifferentiation of protection objectives, which represent an innovative approach, compared to thetraditional concept of protecting the entire territory from an event likely to occur. Thus, a general andbroad objective is replaced by one targeted to the places and people to be protected and the relatedpotential damages. An example of this approach is provided by the protection objective matrix,recommended by the Swiss Federal Office for Water and Geology (FOWG) that indicates the safetylevel to be guaranteed, for each area, based on the probability of natural hazards occurring (Chart.1).The second is the minimization of actions not only for environmental reasons, but also for a globalvision of risks. Recent European floods have highlighted that very big dikes and embankments did nothelp to limit the damages caused by floods with a return time of more than 100 years14. In order toavoid these flood hazards, some countries, including Germany and Hungary, have launched projects toremove some dikes and embankments and to restore generally flooded areas15.

Chart 1 – Protection objective matrix model(Source: Swiss Federal Office for Water and Geology (FOWG): Flood control at rivers and streams, Berne, 2001)

The third aspect is the importance attributed to non-structural measures for the limitation ofdamages. These actions are increasingly being considered as valid instruments to contain flood effects,complementing or substituting the traditional hydraulic defence systems. The InternationalCommission for the Protection of the Rhine has produced a guide for the populations affected byfloods, indicating a list of actions and, for each of these, the conditions which ensure that they can beeffectively carried out (Table 1).

14 The summer 2002 flood in Prague was caused by two rainfall events following rapidly one after the other: The second rainfall occurred at a point whenthe ground of the catchment basin was completely saturated. The hydraulic works could not prevent the run-off due to an extraordinary event with aprobability of occurrence of about once every 500-1,000 years.15 In Hungary, within the National Spatial Development Plan, the National Water Authority identified some areas downstream, which may be used asreservoirs either in case of flooding or in periods of drought. (Communicated by Elisabeth Vajdovich Visy, The National Planning Institute of Hungary(VATI) based in Budapest, at the Conference “Controlling water”, Pordenone 19-20 June 2003)

HQ 1 HQ 1 0 HQ 2 0 H Q 5 0 H Q 100 EHQ PMF

Nature landscapes No design discharge

Extensive Q a Q b agriculture

Intensive Q a Q b agriculturee e Single buildings Q a Q b Local infrastructures

Infrastructures of Q a Q b national importance

Agglomerations Q a Q b Manufacturingunits

Special objects To be determined case by case

Special risks

protection: full l imited none

Qa Damage limit Qb Hazard limit HQn Flood with n frequency of occurrence

EHQ Flood under extreme hydrometric conditions PMF (probable maximum flood)

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Probability of event occurring

Flood depth

high very low low highLand useOutflow areasSpatial planning and urbandevelopment regulationsBuilding techniquesSpace useAppropriate use of equipmentSealingBarriers / ShieldingHazardous substancesEvent preparednessInformation, trainingFlood warning systemEmergency measuresEmergency managementPlanning of activitiesFlood management systemsFinancial support for restorationschemes

Table 1 – Importance of non-structural measures based on the frequency and magnitude of the eventHighlighted areas indicate the application fields to be privileged depending on the type of flood

(Source: International Commission for the Protection of the Rhine, Non Structural Flood Plain Management, 2000)

SPECIFIC OBJECTIVES AND TYPES OF ACTIONS

Public Administration planning should satisfy the demand for “hydro-geological safety” by selecting anumber of actions which best achieve this objective and concurrent ones. The choice should be madeby considering the complete and wide range of possible actions.Actions are the steps chosen to solve problems as they arise and to achieve the desired objectives.Actions include infrastructural works, maintenance and management initiatives (policies, plans,economic projects). Also this area requires a rebalancing effort. It is easy to carry out an action beforefocusing on its objectives, and it is just as easy with regard to the various actions to concentrate on theworks, often on one specific structural item in particular, disregarding the existence of alternativeactions, especially those not requiring the use of iron and concrete.The following is a list of the main types of actions, subdivided under 6 specific16 objectives, which maybe pursued within the sphere of safety guarantees for the population:

16 See Annex 2 for a detailed description.

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1. Recovery of the soil retention capacity and reduction of the meteoric water inflow in the riverbedà protection of the soils and of the minor hydrographic networkà co-ordination of the management of water bypass, retention and discharge systems of the entire river course and its tributariesà land maintenance 17

à restoration actions and actions to ensure viable conditions for stable phytocoenosis2. Discharge increase at critical points (urban areas or areas where public utility structures are

located)àraising of the embankmentsà elimination or reduction of the physical impediments in the most critical stretches of the river

2. Abatement of the flood peakà recovery of outflow areas and re-naturalisation actions.à actions on the main river course and its tributaries: reservoirs, lateral artificial schemes, in-line detention basinsà regulation of the discharge through dikes or drainage channels

3. limitation of the potential damageà correct spatial planning and identification of town planning criteriaà construction criteria suitable to reduce flood damagesà protection differentiated according to values to be safeguarded

4. defence from the exceptional eventàcarrying-out of works and supply with monitoring tools and emergency meansà defence training of all population and shared planning of civil protection actions

5. guarantee of restorationà guarantee fundsà collective, individual or private insurance schemes

The first five objectives define an ex-ante active policy of physical control. The first three, in particular,may be considered as relating to an elusion policy (risk reduction at the source) and a preventive policy(reduction of the probability of occurrence), whereas the fourth and the fifth relate to a protectionpolicy (damage limitation). The last is a financial ex-post objective aimed at containing economicalconsequences.

In a logical scale of priorities, top priority is given to those measures, which tend to preserve the naturalequilibrium of the river:- management of the ground of the entire basin and maintenance of tributaries;- preservation of the natural washes;- spatial planning to reduce the potential damage;- flood awareness and preparedness by flood-prone communities

Only if the actions listed above are considered unable to guarantee a sufficient level of safety, shouldother actions aimed at interfering with the normal river dynamics be adopted alongside the others. Inany case, the financial and environmental impact of the latter must be proportionate to the expectedsocial and economic damage and should not replace the other type of actions.It is important to adopt and guarantee an overall basin-scale strategy, which requires an in-depth knowledge of its features and the presence of shared processes, which ensure the actualinvolvement of all interested parties.

17 “Land and works maintenance actions must protect the riverbed features, safeguard the variety and heterogeneity of the autocthon riparian biocoenosisand promote their reestablishment by taking into account the statements of the Chart of Nature contained in Art. no. 3, paragraph 3 of Law no. 16December 1991, no. 394: General policy law on protected areas. These actions must be carried out without affecting the biological functions of thewatercourse and the riparian ecosystems. As far as the territories within the protected areas are concerned, the administrating bodies responsible for theplanning and carrying-out of maintenance works must be directly involved.” Hydrological layout plan of the Po River, Art. no. 14.2

16

ALTERNATIVE PROPOSAL FOR THE ABATEMENT OF THE FLOOD PEAK

NEW ACTION HYPOTHESIS TO CONTROL THE FLOOD CAPACITY OFTHE MIDDLE AND LOWER COURSE OF THE TAGLIAMENTO RIVER

THE FLOODPLAIN BETWEEN PINZANO AND DIGNANO

In the stretch where the storage basins envisaged by the Abridged Plan for the hydraulic safety of themiddle and lower course of the Tagliamento18, are presently planned, the riverbed is located betweentwo steep escarpments, on average 3 km apart, and is characterized by the variegated mosaic ofcontinuously evolving forms and structures included in the Site of Community Importance (SIC) -“Greto del Tagliamento” (“Shingle of Tagliamento”).

“Here, the Tagliamento drains in the high Friulian plain, through a narrow steep-walled canyon in thepiedmont high grounds known as the “Pinzano gorge”. In this point the ravine is less than 500 m wide,however, the river, which remains deeply embanked in the thick and solid alluvial mattress of graveland cobblestone deposited over thousands of floods, opens into its wide fan-shaped river bed. This isthe stretch which has made the Tagliamento a “unique” river for its characteristic landscape of alluvialterraces which mark the significant hydrometrical variations of the river, alternating periods of totaldrought when the water runs beneath the gravel bed, with other periods when extreme phenomenasuch as devastating floods can reshape the hydrological path of the river which may appear to haveconsolidated over many decades. It is this very hydraulic and ecological dynamics, characterised by thequick adaptation and re-colonisation of flora and fauna, which has made the Tagliamento such anunusual, important and interesting river. A model that is so distant from the almost monotonousschemes of the majority of European rivers that are by now fixed, “crystallised” according to hydraulicengineering logics that have forced them into riverbeds pre-established by calibrations based exclusivelyon the water discharge as the sole evaluation parameter. In this particular stretch, the Tagliamento isstill an active, complex and dynamic fluvial ecosystem, which deserves to be safeguarded.The NATURA 2000 project, which the European Union is implementing in compliance with the“Habitat” Directive no. 43 of 1992, envisages a list of Site of Community Importance (SCI), importantfor the whole of Europe, which must be managed and conserved in accordance with theabovementioned Directive. The part of the Tagliamento shingle located between the Pinzano gorge andthe Dignano bridge, approximately 11 km further downstream, has been rightfully included in the Sitesof Community Importance (SCIs) of the Friuli Venezia Giulia region”19.

International engineers and ecologists have demonstrated the inestimable value of these vastfloodplains, such as the stretch between the bridges of Pinzano and Dignano, and have pointed outhow a hydraulic action in the area would forever jeopardise the ecological functionality of the river and,as a result, trigger chain effects requiring continuous on-going hydraulic maintenance of other riverineareas.Worthy of note is the fact that the hydraulic solution presented in the Abridged plan would be carriedout at a distance of more than 50 km from the settlement area affected by the works, ignoring thenatural flood capacity of the river bed between Pinzano and Latisana which, although reduced, stillexists.However carrying out a detention reservoir, where this can actually be built, appears to be an effectivemeasure, also in areas characterised by anthropogenic interventions, where it is generally difficult toregain space for the river. For this reason, this study wished to provide an alternative hypothesis thatwould compare the volumes likely to come into play moving the sites where the action is expected tobe carried out further downstream. 18 Various authors: Piano stralcio per la sicurezza idraulica del medio e basso corso del fiume Tagliamento (Abridged plan for the hydraulic safety of themiddle and lower course of the Tagliamento River), Technical Secretariat of the North East River Basin Authority in charge of the rivers Isonzo,Tagliamento, Livenza, Piave, Brenta-Bacchiglione.; Implementation law: (prime Ministerial Decree) DPCM 28/8/200019 “Il Sito d’Importanza Comunitaria “Greto del Tagliamento”, Franco Musi, former director of the “Azienda Parchi e Foreste” of the Friuli Venezia Giuliaregion, in “Tagliamento fiume d’Europa. Il problema delle casse di espansione” WWF Italy, May 2002.

17

Fig. 4 Photogrammetry of the area where the water retention basins are expected to be carriedout according to the Abridged Plan (see also fig.1)

APPLIED METHODOLOGY

The analysis of the action hypotheses to control the flood capacity of the Middle and Lower rivercourse, aimed at protecting the town of Latisana and the settlements downstream, represents afeasibility analysis of possible alternatives.The above analysis has been conducted, as stated in the degree dissertation by Marco Vescia, engineer,on the assumption that the Cavrato floodway operates properly, and on the basis of currently availabledata, in particular:- Surveys in scale 1:10,000 carried out in 1982 by Barigazzi, a company based in Parma, on behalf of

the Civil Engineering of Udine;- Surveys in scale 1:5,000 ordered by the Water Authority to be carried out by GEOTOP s.a.s., a

company based in Treviso, in March 2001; and- Discharge data relating to 100-yr return floods supplied by the Water Authority (the project wave

used, which is extremely precautionary for the hydraulic defence based on a pre-established returnperiod, is the same as the one adopted by the Water Authority).

The results of the above surveys enabled the description of the generic cross-section by means of anumber of points, which vary from section to section. Where possible, the analysis was carried outusing more recent data, in particular with regard to the sections situated between the bridge of Dignanoand that of Pinzano. By preferring more recent data, the analysed sections situated between thePinzano gorge and the river outlet amount to 164.In any case, various choices and approximations20 were dictated mostly by the lack of up-to-date anddetailed data, causing additional difficulties arising from the need to properly interpret the complexresponse of the basin to hydrological stress. This highlights the need to take particular precautionarymeasures and emphasises the importance of acquiring detailed information on the characteristics of thebasin.

20 As no data are available concerning the flood discharge of the Cosa stream (110 km2 basin), flowing into the Tagliamento at Spilimbergo, and even lessreferences are available with regard to any possible contextuality with the centenary discharge of the Tagliamento and considering the small dimension ofrelevant basin, it was assumed that it is highly probable that its flood hydrograph is out of phase compared to the one of the main course, thus leaving itsflood peak unaffected.

18

Caution is even more pressing considering that the autumnal hydrological regime – abundantprecipitations, low atmospheric pressure values, and winds of the southern quadrant – is typical of theTagliamento basin. As a consequence, the average values recorded under the exceptional situation,which occurred in November 196621, are not improbable.

In order to describe the propagation modality of floods based on differential equations of motion andcontinuity, the degree dissertation mentioned above relied on mathematical models. In particular, thefollowing research tools were used:

• PAB (Parabolic and Backwater) – this is a model which was already successfully applied todevelop operating systems to forecast floods in China (Hang He and Fuchun), Germany(Danube) and Italy (Po, Tiber, Arno);

• PABL – this is a variation of the PAB and is used for the simulation of wide lateral wateroutflows, e.g. due to the river overflowing its banks or specifically arranged sills, in order todimension their height and length considering the discharge to be drained by the riverbed andthe volume to store on each side;

• WSEZIO software – this is a tool for the treatment of river cross-sections, aimed at modifyingsection data, inputting new information, assigning roughness values and at defining specificpoints in order to generate the data required to perform mono-dimensional hydraulicpropagation simulations.

Thus, simulations were performed with the aim of identifying natural expansion areas to be locatedpreferably right upstream the maximum critical points, where the river morphology allows it. Thefundamental criterion on which this study is based is to use existing natural water retention basins andavoid any modifications, which might jeopardise the present use made of those areas.The project wave used in the simulations to dimension the flood control works is the same as thatadopted by the Technical Committee of the Water Authority. As shown in Chart 2, the wave underexamination is more than sufficiently precautionary as a reference point for hydraulic defence works atriver basin scale, taking into account a 100-year return flood.In addition, it was decided to assume a precautionary downstream hydrometric level of 1 m asl, basedon the fact that the last kilometres of the river downstream of Latisana may suffer from the rising tide.If the tide is concomitant with maximum flood peak discharges, this may cause the water to overflowupstream and thus make the river overflow from the top of the bank with resulting floods.

Fig.5: Project hypothesis adopted22

21 The damages caused by the flood of 1966 affected 54 municipalities situated along the lower rivercourse, amounted to over 77 billion worth of Italianlire in those days (This figure excludes damages suffered by riverbeds, which, after the flood, required repairs, with financial costs similar to those incurredfor damages suffered by the woodlands), 14 dead, 24,000 injured and approximately 5,000 homeless people. The waters flowing out of their routes andthose inundating overbank areas flooded an area of 1,830 ha on the right side of the Tagliamento, whereas on its left side flooded areas were greater than21,410 ha.22 Different roughness coefficients (Manning’s n) were selected for the stretches between Pinzano and the Latisana bottleneck (0.033 m1/3s-1) andbetween Latisana and the river mouth (0.030 1/3s-1) respectively; the Cavrato channel operates with discharges greater than 1500 m3/sec up to amaximum of 2500 m3/sec.

19

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100-year event with 24-hour rain evaluated at Venzone

100-year event with 24-hour rain and 20% amplificationfactor (estimated at Pinzano)





event of 1966 evaluated at Venzone and recorded 20%(estimated at Pinzano)

event of 1966 registered at Venzone, 20% increased andChart 2. – The discharges

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Event of 4 November 1966 recorded at Venzone






100-year event wit 8-hour rain and 20% amplificationfactor (estimated at Pinzano)

event of 1966 evaluated at Venzone, 20 % recorded(estimated at Pinzano)Chart 3 - Volumes

ANALYSIS RESULTS

The results of the abovementioned survey, allowed the description of the generic cross-section of thefloodplain through a number of points. In particular, the use of the most recent sections, available forthe area corresponding to the Site of Community Importance (where the river maintains a floodplainwidth of approximately 3 km) resulted in a more reliable evaluation of the effect of the natural floodcapacity of the river, which is greater than the one that would result considering much narrowersections.In fact, the estimate cannot be realistic if, in some stretches, it does not take into account the entirefloodplain area, thus ignoring the overall natural flood capacity of the river (Chart 4).

20

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Natural floodcapacity of the riverat Latisana

Chart 4 – Effect of the natural flood capacity of the river at Latisana

Assuming that no more than 4000 m3/s-123 can flow at Latisana, the model showed the possibility toincrease the flood capacity of the river through the construction of detention basins with acapacity of approximately 21 millions m³24. This would be achieved by the means of a dischargereduction system entailing the flooding of areas generally used for agricultural purposes and whichwould nevertheless be inundated, in case of flood.Once again, the above basins represent a bypass system25, which would effectively flatten the floodhydrograph with yet the same stored water volume.Usually, the areas designated for the excavation of water retention basins are those, which areperiodically subject to natural floods, i.e. areas characterised by meandering streams. The areas whichshould be preferred for potential flooding are those located nearby or immediately upstream the site tobe protected and also on the hydraulic side where the river has naturally over-flown in the past.Thus, taking into consideration the geological configuration of the riparian district and the type ofatmospheric events that affect it, the flood problem boils down to two main issues. If on the one handit is necessary to retain meteoric water masses on the mountains and then regulate their downflowaccording to the downstream riverbed drainage capacity, on the other hand it is necessary to increasethe outflow of the river in its lower stretch even in case of high tide at the mouth.Therefore, the first problem to be solved was to identify, of the areas situated next to the watercoursesand, as such, naturally and potentially flood-prone in case of river overflow, those to be inundated incase of flood. 23 It is worth noting that, in order to prevent urban centres downstream of Latisana from being flooded, the analysis performed by the Basin Authority forthe North Adriatic Rivers set, exactly at Latisana, a discharge capacity of max. 4000 m3s-1, which would be achieved through widespread settlement works,carried out to the low rivercourse (some of which have already been completed or about to start) as well as through the proper functioning of the Cavratodischarge channel.24 Instead of the 30 million m³ of water originally foreseen in the Abridged plan for the hydraulic safety of the middle and lower course of the TagliamentoRiver.25 These are usually placed in areas which develop parallel to the riverbed and which generally belong to the river. They are hydraulically connected throughovertopping thresholds, siphons or other hydraulic systems placed within the river embankments. These construction works are designed to guarantee onthe one hand that the water retention basin is flooded with an acceptable level of frequency and on the other one that the maximum discharge, outflowingdownstream of the works, does not exceed the one considered acceptable for the riverbed. According to this arrangement, the water retention basin isflooded only when, during the flood, the discharge exceeds the pre-established threshold value. Obviously, the by-pass basins can operate only if the river,where they are planned to be consrtucted, is “hanging” or “embanked”. In fact, it is only in these cases that part of the flood wave can flood into the waterretention basin and return into the riverbed through a hydraulic system different from the lateral spillway.

21

THE ALTERNATIVE PROPOSAL

The need to store a 21-million m³ water volume and the space required to retain it has led toenvisage the construction of 7 water retention basins in the river area stretching betweenapproximately 2926 and 53 km from the sea. (Fig.6)

Fig. 6 Location of the seven water retention basins

These works, planned to be carried out along approximately 24 km of the river bank right and left(Table 3) and on local raised flood walls (Table 2), would allow the retention of a basin surface equal toapproximately 10.5 millions m² aside from the regular water discharge.

Water retention basin Average raisingof left dike

Average raisingof right dike

Water retention basin 1 1.5 m -

Water retention basin 2 - 1.5 m






Table 2- Raising of the floodplain dikes

26 The railway bridge, which crosses Latisana and which currently represents a dangerous obstacle to the outflow of flood water, is located at a distance of26,815 m from the sea.

22

Basin Surfacearea Volume Average

heightHydrographic

locationStarting / final

section Weir Longitudinaldevelopment

Basin 1 2,328,700 m2 3.33 millionm3 1.43 m Left 130/124 5700 m

Basin 2 2,601,250 m2 3.33 millionm3 1.28 m Right 130/124

Length = 1,200mHeight = 3.00 m

5700 m

Basin 3 2,568,475 m2 3.89 millionm3 1.52 m Left 124/118 Length = 900 m

Height = 3.90 m 4600 m

Basin 4 1,218,700 m2 3.94 millionm3 3.23 m Left 114/107 2250 m

Basin 5 1,208,000 m2 3.94 millionm3 3.26 m Right 114/107

Length = 600 mHeight = 6.10 m

2750 m

Basin 6 460,000 m2 1.78 millionm3 3.87 m Left 85/76 1950 m

Basin 7 250,000 m2 0.82 millionm3 3.28 m Right 82/78

N/A

1200 m

Total 10,635,125m2 21 million m3 24150 m

Table 3 – Summary table of the action proposals

The application of the models highlighted that, in the stretch where the water retention basins areexpected to be carried out, a bottleneck would occur in the active riverbed with no negative effects onthe routes generally followed by the rivercourse during floods. In theory, if the water retention basinsare not built, a narrower riverbed would give rise to a moderate increase in the discharges and levelsdownstream (see Chart 5) which would, at the same time, allow the exploitation of the areas, situatedwithin the main embankments, for the retention of the estimated 21 million m3 of water which isnecessary to improve the flood capacity of the river.

23

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Wave at Latisana whereflood capacity of the riveraffected by the waterretention basins

Chart 5- Effects of the narrowing of the riverbed and of the changed flood capacity of the river

Survey data and considerations developed on the results of the non-stationary-flow model (which takesinto account both river outflow volumes and its natural flood capacity) were used to identify thoseareas which, from a natural point of view, appear to be a suitable site for the water retention basins.Initially, only natural water retention basins were considered. These were to be located in theplain and as close as possible to the area to be protected so as to ensure a better exploitation ofthe storing volumes; afterwards, having established that the flood capacity of the river was notsufficient, additional areas were included, situated in the stretch immediately upstream, where theTagliamento flows into the plain. This decision led to the identification of more suitable areas for theconstruction works aimed at guaranteeing the safety of Latisana and the people living in the valley.In this phase of the analysis, the area was estimated by carrying out the planimetry of the location ofthe works, whereas the water surface level, which the area could retain, was assessed using theinformation based on the data relating to the sections.The present analysis did not examine the issue concerning the internal compartmentalization of thewater retention basins, it is however advisable to distribute the volume among those water retentionbasins connected together as a single unit, also because of the benefits reaped in managing floods,especially with regard to the volumes to be controlled in each event (Figure 7).

24

OVERFLOW THRESHOLDOR SIPHON

SECTION A – AA = dike of the water retention basin; B = dike of the watercourse.

Overflow threshold or siphon

Figure 7 – By-pass water retention basin operating scheme

In addition to the lateral spillways, water retention basins 1, 2, 3, 4 and 5 should be provided with aweir (3 weirs in total) supplied with suitable openings with no movable flaps (weirs with calibratedopening) situated 50 m downstream of the lateral spillways. The weirs should allow low, moderate andhigh discharges to flow smoothly downstream following their natural course, however, in case of floodswhich might be critical for the people downstream, they would cause an increase in the hydrometriclevel upstream of the weir and allow the spillways to come into operation.

25

SECTION A-A’

Fig. 8 Graphic image of an open weir

These are, in fact, open weirs that do not interrupt the longitudinal flow of the river. Theconstruction of these weirs becomes essential to create a suitable water head upstream of the weirs,which for the particular riverine morphology of the Tagliamento River (with steep gradient of someparts per thousand), could not, otherwise, be achieved.

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CRITICAL ISSUES ANALYSIS

Local obstacles such as bridges undoubtedly affect the regular outflow of a river in flood. The middleand lower courses of the Tagliamento River are crossed by many bridges used for road traffic which arenot affected by floods, however, the iron bridge of the Venice-Trieste railway line, situated in the centreof Latisana, represents a danger as it interferes with the downflow of the river in flood, its under-beambeing 1 meter below the upper part of the river banks (10.22 m as opposed to 11.22 m) (Figure 9).

Level (m) ; Cross-section (m)Figure 9 – The railway bridge at Latisana as processed by the WSEZIO software

As a result, when a 100-year flood occurs, the uneven profile of the dikes, which were raised after thebridge had been built, may be the cause of dangerous overflows in the area right beside the railwaytracks.Attention must also be paid to the effect of floods on the floor system of the railway bridge, whichcould become a barrier to the current transporting logs and debris and thereby progressively obstructthe bridge spans causing water blockage.Thus it is evident that the above bridge represents a serious obstacle to the water flow and a seriousconstraint to the definitive flood control of the final stretch of the river.The Italian state railway company has already implemented a project, which would lead to theelevation of the bridge by 80 cm, thus reducing the entity of the overflows and allowingdischarges exceeding 4000 m3s-1.

However, the most critical stretch is located further downstream, just past the town ofCesarolo, where the Cavrato drainage channel branches off.The stretch, which extends between the Cavrato intake and Latisana, has recently undergone importantdike reinforcements and riverbed adjustments aimed at increasing its flood capacity to more than 4000m3s-1. Considering that the current maximum discharge of the Tagliamento, downstream of the intake,is approximately 1500 m3s-1 and that the maximum capacity of the Cavrato drainage channel is 2000m3s-1, the potential discharge of the river in the downstream part of this stretch is currently estimatedat 3500 m3s-1.Worthy of notice is also the gross negligence in the management of the right bank (Venetianriverside) which, due to the combined effect of the infesting weeds and the bottlenecks caused by thebridge piers, drastically reduces the hydraulic capacity and efficiency of the riverbed at theLatisana bottleneck (Figure 10).

27

Figure 10 – A detail of the right bank in the proximity of the bridge at Latisana (photo by Marco Vescia)

HYDRAULIC ANALYSIS CONCLUSIONS

The specific goal of this study was to evaluate the feasibility of alternative solutions to the presentproject envisaging the carrying out of three water retention basins immediately downstream of thePinzano gorge.This study evinces the possibility to hypothesize, with regard to the hydraulic aspects, an action strategyto be carried out on the basin of the Tagliamento River, which would allow to bring the flood capacityof the river, defined in the project, in line with the pre-established values by simply identifying areas,possibly close to Latisana, where water retention basins capable of retaining approximately 21 millionsm3 could be located.In particular, instead of altering special conservation areas situated immediately downstream ofthe Pinzano gorge, the analysis considers less environmentally sensitive landscape areaslocated 30 km further downstream to carry out the works.Any attempt to try and control the flood capacity of the river, assuming project waves of whatevermagnitude, should not underestimate that the Tagliamento is a torrential river and, as such, the shapeof its reaches and as its roughness coefficient continuously change. Careful geological-lithologicsurveys should be conducted to ensure that any form of channelization does not cause anincrease in the erosion rate, the holding of sediments or, even the lowering of the aquifer level.Furthermore, in order to produce a wide-reaching analysis, evaluations of the duration of high riverflows, the speed of water on the river bottom and banks, the seepage regime of the inner andouter dike areas27 and of the soil mechanical resistance should be combined with the hydrologicand hydraulic analyses carried out to estimate the flood envelope profile.

The analysis stresses the need to carry out improvement works to the Cavrato drainage channel and tothe entire lower course of the Tagliamento, as envisaged in the Abridged Plan by the Water Authorityof Venice. Such works must not only achieve the set objective but also be part of an overall projectinvolving river expansion areas, within and outside the riverbed, and thereby restore the relevant areasas soon as the water covers them again. 27 The estimates of the discharges which can potentially seep through the ground require a deep knowledge of both the features of the water seepage bedand of its initial degree of saturation as well as of the ways in which the water flows through the aquifer as the subsoil behaviour needs to be evaluated anddescribed as if it were a proper reservoir.

28

It should be pointed out that the abovementioned analysis is not and does not intend to be a workingproject, but rather a feasibility study of alternative hypotheses, the results of which, however, confirmthe viability of the various action proposals hypothesised thus highlighting the need to turn the studyinto a proper working plan.However, a project proposal, though perfectly valid, may be incomplete if it does not set out itslimitations, which need to be taken into account at the working plan stage. In fact, if the analysesperformed guarantee the verification of the planning hypotheses, on the other hand more up-to dateinformation is required to achieve a “truer” representation of the geometric and hydraulicconditions of the river28 and therefore provide more details about the proposal concerning theplanning and execution of the works aimed at the optimization of the flood regime. Inparticular, sections data should be transparent and unequivocal and be as accurate as possible so as togive a clear representation of the river morphology taking into account also disturbing elements such asbridges, roads, dikes, etc.

Finally, it is worth noting that no structural works (such as those identified to date) can guarantee theoverall safety of the area and it is for this reason that, in addition to the above works, a real-timeflood forecasting system ought to be implemented (this can be easily achieved thanks to a largenetwork of telemetry stations currently in operation for the recording of rain precipitation and themeasuring of rain levels as well as to increased quantitative weather forecasts available throughmeteorological forecast models).This system, which is extremely cheaper than structural works, would be, along with floodhazard maps and emergency plans, of fundamental importance in providing assistance todecision-making in the management of emergencies.

28 Discharge data statistics, available in printed form, can be used to describe the hydrological features of the Tagliamento River basin, but they aredefinitely insufficient to calculate a flood peak with a given return time. The latter is a project data to be established with extreme accuracy in order tocalculate the volume of the storage capacity necessary to improve the flood capacity of the river. The difficulties encountered in trying to perform a correctevaluation of the above statistical quantities are as follows:a) lack of homogeneity in the collected data (data come from different sources, hydrometric stations provide information at different intervals, etc.);b) only few hydrometric stations can be found on the main corridor of the basin and these are even far from the Pinzano stretch;c) discharge data related to the Tagliamento River are only partially reliable due to the fact that the riverbed changes continuously and significantly.

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ECOLOGICAL ASPECTS OF THE RIVERINE CORRIDOR

ECOLOGICAL FRAMEWORK

The importance of the Tagliamento River for the Friuli Venezia Giulia region goes by far beyond itsextraordinary ecological and environmental values.The region has always been a land where populations of different ethnic groups and cultures mergedand the Tagliamento represents seemingly the backbone of a territory, which has over the yearswitnessed great displacements, encounters and tensions. Strangely enough, these features areencountered also in its ecological aspects.However, this analysis deals only with the general ecological framework, which needs to be examined indepth in an overall work on the Tagliamento River (see attached bibliography).

The uniqueness of its landscape elements and the abundance of animal and plant speciesdepend on the network of ecological connections and trophic chains, which act as the linkbetween the living creatures and the chemical-physical environment.These elements can hold together any ecosystem, whose degree of complexity depends on the increasein biodiversity, thereby boosting the ecosystem vitality.From this point of view, the Tagliamento River is a unique ecosystem yet to be discovered and studiedin depth, despite it is already an extraordinary research laboratory for science scholars coming from allover the world.

Fig. 11 View of the high rivercourse, North of the Pinzano gorge (photo by Arno Mohl, WWF Austria)

The river, in fact, has a very high ecological connectivity level, both longitudinally and transversally. Onthe one hand, since the river flows abruptly from the mountain to the plain and its outlet into the sea isquite close to the Alpine chain, the Tagliamento represents a sort of bridge between the Alps and the

30

Adriatic Sea, hence between the flora and the fauna of different habitats. On the other hand, since theriver morphology is mostly characterized by bar-braided and island-braided reaches, its transversalsection diversifies into many microhabitats showing different relationships between the running watersand the earth environment, which inevitably influence each other.The above dynamics are typical of the middle reaches of the Tagliamento which, from ageomorphologic point of view, represent the most unspoilt stretch of the river but also the leastaffected by human action unlike the stretch running through the mountains which is stronglyinfluenced by the water withdrawals made by plants for hydroelectric power generation, and its finalstretch which looks like some sort of artificial canal.

Fig. 12 View of the middle rivercourse, South of the Pinzano gorge (photo by Arno Mohl, WWF Austria)

Such is the distinctiveness of the middle course of the Tagliamento that among all of the Alpine riversit may be considered as ‘unique’ and a reference point for anyone who intends to implementactions and conduct studies on riverine renaturalisation . It is a place characterized by a mosaic ofvarious endangered and most vulnerable habitats: the riverbed itself characterized by island-braidedreaches and vegetated islands29, the floodplains with their typical forests, woods and hedges, theFriulian meadowlands named “magredi” and, finally, a stretch of land characterized by small upwellingsof groundwater (Sorgive di Bars).These groundwater upwellings come up again on a larger and more manifest scale further downstream,thus becoming the most distinctive feature of the regional territory. In fact, when the TagliamentoRiver flows into the plain, it runs on very permeable floodplains, its discharge decreasing by infiltrationin the underflow conduit. The water of the Tagliamento River, therefore, feeds the most importantsubterranean aquifer system of the region, and in the lowland, after flowing through the impermeablestrata of clay, it resurfaces and creates a wide network of upwelling groundwaters and more generally avast humid area typical of the Friulian lowland, considered of inestimable environmental value.

29 At present, the vegetated islands and gravel bars are among the most endangered landscape elements in Europe. Of these, 652 are stable and can befound in the Tagliamento River. Their surface is equal to 10.6 km² and represents 17% of the total area of the active corridor (Ward J.V., Tockner K.,Uehlinger U, Malard F., 2001)

31

Once the river reaches the sea, debris transportation and sedimentation contribute to the creation ofthe delta environment of the Tagliamento River, with the beaches of Lignano and Bibione and theirgreatly appreciated pinewoods as well as the lagoons of Marano and Caorle.From its source in the mountains to its mouth at the sea, the course of the Tagliamento River ischaracterised by a variety of landscapes and habitats of great value, which gradually merge into eachother and are reciprocally influenced thanks to a substantial ecological continuity, which characterisesmost of the rivercourse.

CONSERVATION AREAS IN THE HIGH COURSE OF THE TAGLIAMENTO RIVER

In the more mountainous part, the Tagliamento basin crosses, even if only partially, the Parconaturale delle Dolomiti Friulane (Natural Reserve of the Friuli Venezia Giulia Dolomites), which isthe widest and “wildest” conservation area in the region, featuring many rare and endemic species.Two biotopes, identified by Regional Law No.42 of 1996, represented by the Palude di Cima Corso(Marsh of Cima Corso) in the Municipality of Ampezzo and by the Torbiera di Curiedi (Peat-bog ofCuriedi) close to the village of Fusea, are two of the few examples of mountain humid areas in theregion and are extremely interesting, especially from a botanical point of view. The Palude di CimaCorso abounds of very rare species at a regional and national level: the Liparis loeselii, one of the mostsingular orchids, two members of the Ciperaceae family, the Carex fiandra and the Carex appropinquata,(this marsh being the only regional area where the former grows) as well the hydrophytes Sparganiumminimum, Plantago altissima and Genziana pneumonanthe. All these species are included in the “Libro rossodelle piante d’Italia” (Red list of plants of Italy) under the category of endangered species and, theirpresence in such a restricted area (just over 7 ha.) is evidence of the great value this humid area has inthe national preservation of biodiversity. A population of the extremely rare Salix rosmarinifolia and oftwo of the rarest species of the Italian flora, the Rhynchospora alba and Rhynchospora fusca, both membersof the Ciperaceae family, grow in the Torbiera di Curiedi.

CONSERVATION AREAS IN THE MIDDLE COURSE OF THE TAGLIAMENTO RIVER

The middle course of the river crosses the piedmont area, which includes the Riserva Naturale delLago di Cornino (Natural Park of the Cornino Lake), one of the most interesting natural reserves ofthe region, situated close to the village of Cornino. This area, which is characterised by a profusion ofplants, is of considerable importance from both a landscape and an ecological point of view, in fact,approximately 1200 diverse species were recorded in a small area (11x13 km2) situated between Amaroand Cornino. The reserve is well known for the reintroduction project of the Griffon Vulture (Gypsfulvus), which became extinct in the Eastern Alps over the last century and is now present with a smallnesting colony.The feeding station, which represents a food resource for the Griffon Vultures, attracts also other birdsof prey, such as the Egyptian Vulture (Neophron percnopterus), the Black Kite (Milvus migrans), the RedKite (Milvus milvus) and rare species, such as the Spotted Eagle (Aquila claga), the Lesser Spotted Eagle(Aquila pomarina) and the Imperial Eagle (Aquila heliaca). Also Peregrine Falcons (Falco peregrinus) can befrequently spotted in the park, which hosts the best-structured Eagle Owl (Bubo bubo) population of theregion.

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Fig. 13 “Riserva naturale del lago di Cornino” and the wide gravel riverbed of the Tagliamento River, wherevegetated islands are half-hidden. The feeding station for birds of prey is visible on the left of the lake.

(Photo by Nicoletta Toniutti, WWF Italia)

Whereas the Wild Cat (Felis silvestris) seems to be quite widespread throughout the region, the Jackal(Canis aureus) makes only sporadic appearances.Also the adjacent Campo di Osoppo (Osoppo’s Field) is particularly interesting, since it providestrophic and reproductive resources for the largest regional nursery of bats such as the common Bent-wing Bat (Miniopterups schreibersii), the Greater Mouse-eared Bat (Myotis myotis) and the Lesser Mouse-eared Bat (Myotis blythii), whose populations find shelter in the hollows of Colle di Osoppo (Osoppo’sHill). Sorgive di Bars (Bars Springs), a Protected Area defined by Regional Law No. 42 of 1996, arelocated near the abovementioned Campo di Osoppo where the waters of the Tagliamento River, whichhave seeped through the ground upstream, resurface. This is an amazing humid environment alternatedby the steppes of the “magredi”. There is an enormous variety of birds and amphibians and springwaters provide support for an extremely differentiated ichthyic community, where, despite the limitedterritorial extension, the rare White-clawed Crayfish (Austopotamobius pallipes) can still be found, thoughnot as frequently as in the past due to reckless withdrawals and depletion of water resources.The territory of the “Riserva di Cornino” is part of a wider conservation area represented by the Site ofCommunity Importance 30 (SCI), named Valle del medio Tagliamento (Valley of the middleTagliamento River) which, along with the SCI Greto del Tagliamento (Shingle of the TagliamentoRiver), located immediately downstream of the Pinzano gorge, includes almost the entire stretch of themiddle rivercourse.

ECOLOGY OF THE MIDDLE REACH OF THE TAGLIAMENTO RIVER

PlantsThe infinite botanical variety, which can be found in this fluvial habitat, seems to clash with the vastand dry gravel areas, which characterise it.

30. The “Valle del medio Tagliamento” (“Middle Tagliamento Valley”), code IT3320015 and the ”Greto del Tagliamento” (Shingle of the TagliamentoRiver”), code IT3310007 are Sites of Community Importance (SCIs) waiting to be evaluated and designated as “Special Areas of Conservation (SACs) inaccordance with Community Directive 92/43/EC of 21 May 1992, known as the Habitat Directive.

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Fig.14 Typical gravel stretch of the Tagliamento riverbed (Photo by Toni Vorauer, WWF Austria)

Here biodiversity reaches its peak as the riverbed acts as a great natural corridor, where many plantsexploit the water current to spread their seeds down the valleys. This phenomenon, known as “de-alpinism”, fosters the co-existence of typically Alpine species with those of the Prealps and of the plainsof the middle course of the Tagliamento River. In these white gravel stretches, de-alpine plants, such asthe Matthiola carnica, Dryas octopetala, Biscutella laevigata and Minuartia capillacea, which are typical of themountain screes, can be frequently found.Moreover, in this part of the basin the so-called endemic species are numerous and, among these,worth of notice is the Brassica glabrescens.The flora of the habitat known as “grave” is almost exclusively herbaceous, in fact, shrubby andarboreal vegetation cannot withstand the mechanical stress caused by the frequent floods affecting thearea. The play of currents and water flood pressure gives rise to a mosaic of everchangingmicrohabitats, where low mounds and depressions play a fundamental role with regard to floodfrequency and number of hosted species.Colonization is much more difficult in harsh environments such as river gravels where, pioneer speciesof that habitat, the so-called “sand and gravel plants” grow. The typical vegetal association of this earlystage of the ecological succession is called Leontodonto berinii – Chondrilletum that is characterized bythe yellow flower heads (florets) of the Leontodon berinii and the Chondrilla chondrilloides, both members ofthe Compositae family. When water becomes scarce, these pioneer species prepare the ground foranother vegetal association known as Epilobio – Scrophularietum caninae, comprising of the Epilobiumdodonaei and the Dog Figwort (Scrophularia canina), often found with the Viper’s Bugloss (Echium vulgare)and the Oenothera biennis.At slightly higher elevations, where the water does not persist for long periods of time and the soilgranulometry is finer than that of gravels thus helping the ground to retain more water and humidity, amore uniform uninterrupted vegetal cover dominates: this is called the “magredi”, a typicalenvironment of the high Friulian plain, formed by grasslands of steppe which take root on particularlypoor permeable grounds. The “magredi”, presently confined to areas close to watercourses andthreatened by improved and more efficient agricultural practices that enable greater land use, are one ofthe most endangered landscapes of the whole region. The vegetal association typical of the magredi isknown as Centaureo – globularietum, and comprises of the Centaurea dichroantha, a member of theCompositae family, and the Globularia cordifolia, often found with other herbaceous vegetation such asthe Dwarf Sedge Carex humilis and the Sesleria varia, member of the Graminaceae family.The typical shrubby vegetation, which can be found within the Tagliamento shingle, is the Salicetumincano - purpureae with two types of pioneer willows called Salix eleagnos and Salix purpurea, withfragments of Salicetum albae formed mainly by seedlings of White Willow (Salix alba) and Black Poplar

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(Populs nigra). These two arboreal varieties along with the shrub called Myricaria germanica dominate theriverine vegetation, which grows along the banks of the river.Some structured populations of the Black Poplar and the White Willow growing within the riverbedcan also be found in the so-called vegetated islands. These are raised areas which become affected bythe running water only in case of severe floods and which are fundamental for the preservation of thedynamic equilibrium resulting from the continuous modifications brought about by the flowing ofwater. The vegetated islands are one of the most vulnerable and endangered riverine environments ofthe entire Alpine arc, as optimization works and concrete treatments of watercourses continuouslythreaten them.

The aquatic environmentVegetated islands, riparian strips, and floodplain forests, where innumerable insect species find refugeand birds build their nests, act as a fundamental connecting channel between aquatic and terrestrialenvironment. In fact, the aquatic environment depends heavily on the trophic contribution by vegetalmaterial, which falls from the banks into the water. This is a source of nourishment for the so-calledcommunities of benthic macro-invertebrates represented by the aquatic larvae of insects (Plecoptera,Ephemeroptera, Trichoptera, and Diptera) Coleoptera, Gasteropoda and Crustacea. Theseinvertebrates are the main nourishment for the ichthyic fauna, whereas structured and diversifiedcommunities of macro-invertebrates provide a habitat for just as many ichthyic populations.Most of the whole regional ichthyic fauna lives in the waters of the Tagliamento River. The specieswhich are commonly found are those typical of the fresh and oxygen-rich mountain waters, such as theBrown Trout (Salmo trutta trutta) and the Bullhead (Cottus gobio), those flourishing in the brackish watersof the delta, where the upstream passage of eurialine species such as the Flounder (Platichthys flesusluscus), the Twaite Shad (Alosa fallax), the Bass (Dicentrarchus labrax) and the Grey Mullet (Mugil cephalus)takes place, and also the Accipenser naccarii and the Accipenser sturio, two Sturgeons typical of the highAdriatic sea, which nowadays are only rarely spotted. The ichthyic biodiversity of the Tagliamentoreaches its peak in the lower stretch of the river, where the upwelling groundwaters (Linea delleRisorgive) carry a great quantity of nutrients and, above all, generate an enormous variety ofmicrohabitats, such as ponds, springs of water, canals, brooks and humid areas.The middle course of the Tagliamento River is a transition area situated between the one, which is thehome of the Marble Trout and the Grayling, and the hotspots where the Chub and the Barbel thrive.Thus, the middle stretch can be defined as an area half-way through the cool, fast-flowing, oxygen-richwaters with scarce submerged vegetation and a thin gravel substrate, and calmer temperate waterscharacterized by an early colonization of submerged vegetation and a fine-grain substrate.In these waters, species of salmonoids, which generally live in cooler waters, coexist with species ofcyprinids, typical of areas where water currents are not as strong.The Marble Trout (Salmo trutta marmoratus) is undoubtedly the most typical and peculiar species ofsalmonoids, which can be found in this area. This fish is an endemism of the Alpine effluents of the PoRiver, of the watercourses of the Friuli region and of some of the Slovenian and Croatian Adriaticcoast31.Another very rare species found in the middle course of the Tagliamento River, which is one of itsstrongholds in the region, is the Grayling (Thymallus thymallus), a fish species typically associated with theMarble Trout. This fish, unlike others, thrives in undisturbed and unpolluted waters. The presence ofthe grayling is, therefore, a clear sign of environments that still maintain their natural conditions.The salmonoids are the most endangered fish family due to anthropic actions; in fact, they can hardlytolerate the low oxygen levels of oxygen-depleted waters resulting from organic pollution. Furthermore,according to their biological cycle, they usually live near ponds and shelters, where the water current isnot strong, whereas, when they reproduce, they migrate upstream choosing areas characterized by fast

31 In recent years, the practice of introducing the Brown Trout, which is undoubtedly more adaptable and easy to breed compared to the Marble Trout, inorder to support sport fishing activities has become more and more frequent, thus, making the Brown Trout the most frequently found salmonoid in thewaters of the region. This has exposed the Marble Trout to a rather insidious and uncontrollable pollution, i.e. “genetic pollution”. In fact, when theintroduced Brown Trout mates with the autochthon Marble Trout, the genetic inheritance of the resulting hybrids is more and more influenced by that ofthe Brown Trout, thus increasing the risk of the Marble Trout becoming extinct.

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flowing shallow waters and uniform gravel substrate, where they spawn their eggs. Ideally, theirhabitat should border a wide spectrum of geomorphologically different areas. This however isless and less likely to occur, as works, carried out by man to improve the river regime and itsembankment, tend to continuously unify and destroy the biological multiplicity, which makesit vital and peculiar. Moreover, the frequent transversal works, such as check dams and concrete dikesoften represent an insuperable obstacle for the salmonoids migrating upstream during theirreproductive phase, which therefore often fails. Unlike other rivers, the Tagliamento is still unspoilt andmaintains these morphologies and ecological dynamics in its middle-high stretch.In the waters of the middle course, salmonoids coexist with some species of Cyprinidae representedmainly by the Chub (Leuciscus cephalus) and the Barbel (Barbus plebejus), which often grows very big.Another Cyprinidae typical of the middle-high course of the river is the Roach (Chondrostoma genei). Thisis a fish with gregarious habits, which is gradually decreasing in number due to water qualitydeterioration, check dams and obstacles hindering access to reproductive areas, and due to anthropicactions altering the bed of watercourses in general.

Amphibians and reptilesThe good state of preservation of the environment surrounding the waters of the Tagliamento is alsotestified by other fauna groups, which do not live in the main river course. For example, the floodplainsof the Tagliamento River host approximately 50% of the Amphibians and Reptiles species ofthe region. (The percentage increases to 70% if the calculation is based on Amphibians alone).The pools of backwater, residual of floods, and the humid areas can host, at least in the reproductivephase and in the early stages of development, two species of Tritons (Triturus carnifex and Triturusvulgaris meridionalis), the Salamander (Salamandra salamandra), the Yellow-bellied toad (Bombina variegata),the Italian Tree Frog (Hyla intermedia) and two species of Toad, namely the Common Toad (Bufo bufo)and the European Toad (Bufo viridis). The latter prefers arid environments, thus, it is the amphibian thatis commonly found in riverbeds, although it is slowly disappearing due to extensive agriculturalpractices. There are also four species of frogs: Edile Frog (Rana esculenta ), Spring Frog (Rana dalmatica )Grass Frog (Rana temporaria) and Agile Frog (Rana latastei). The latter, which is an endemic species ofNorthern Italy and currently in decline, still abounds in the natural habitats present along theTagliamento River and deserves particular attention.Reptiles often find shelter in the bushy areas of the shingles and well adapt to white gravel. The GreenLizard (Lacerta viridis or Lacerta bilineata32), the very common Wall Lizard (Podarcis muralis) and the Slow-worm (Anguis fragilis) are the most frequently encountered reptiles.Five are the species that can be found among the shingle cobblestones, all belonging to the Colubridaefamily. Those, which can grow to well over a meter in length (up to 2 meters), are the Western WhipSnake (Coluber viridiflavus) and the Aesculapian Snake (Elaphe longissima ), which are able to prey on otherinvertebrates, even big ones, but preferably eggs and small birds. The Smooth Snake (Coronella austriaca),instead, rarely grows longer than one meter and hunts small reptiles, mice, eggs and nestlings. Finally,there are two types of Grass Snake, the Ringed Snake (Natrix natrix) and the Dice Snake (Natrixtessellata), the latter being an extremely good swimmer. They both eat amphibians and small fish.

BirdsAccording to European Directive 79/409/EC of 2 April 1979, the so-called “Birds” Directive, nowincluded in the Habitat Directive, the Shingle of the Tagliamento River is an area of greatornithological importance hosting many rare species.In the migratory season the Tagliamento River abounds of ornithic species, in fact, by flowing alongthe north-south axis, it represents a very important migratory corridor, a reference point, as well as ashelter and a resting place for migrating birds. Moreover, due to intensive agricultural practices, theshrubs and bushes of the Friulian plain are rapidly disappearing and, the few bushes left along thecourse of the Tagliamento River represent, for most species, a vital shelter.

32 The difference between the distinctive attributes and the distribution patterns of the two species are not entirely known.

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Among the most important species, the following are worth noting: the Little Bittern (Ixobrychusminutus), the Stone-Curlew (Burhinus oedicnemus), the crepuscular Nightjar (Caprimulgus europaeus), theKing Fisher (Alcedo atthis), the Tawny Pipit (Anthus campestris) as well as the Red-backed Shrike and theLesser Grey Shrike (Lanius collurio e Lanius minor). The latter ones are less rare here than anywhere elsedue to the presence of thorny scrubs.Among the various birds of prey, the Kestrel (Falco tinnunculus) can be observed across the entire ItalianAlpine range but only in the Friulian plains. The Buzzard (Buteo buteo) is also very common, but alsoother birds, such as the Northern Harrier and the Hen Harrier (Circus cyaneus and Circus pygargus), theMarsh Harrier (Circus aeruginosus), the Osprey (Pandion haliaetus), the Black Kite (Milvus migrans) and theHoney Buzzard (Pernis apivorus) can be seen.The fluvial corridor is the only non-coastal nesting site in the Region for nesting couples of theCommon Tern (Sterna hirudo). Also the Little Ringed Plover builds its nest along the riverbed (Charadiusdubius), its abundance being directly related to the length of the riverbank and, therefore, on the numberof interlacing water canals. Unlike the Little Ringed Plover, other birds like the Little Egret (Egrettagarzetta ), the Grey Heron and the Great White Egret (Ardea cinerea and Egretta alba) do not build theirnests along the riverbed but can be observed all year round.Aquatic waterbird families such as the Anatidae and Charadriidae are numerous during the wintermonths. The floodplain close to Cornino hosts dormitory nests for Cormorants (Phalacrocorax carbosinensis), which were once threatened with extinction due to indiscriminate hunting, but are now rapidlyrepopulating.A Crane (Grus grus) nest was recorded in 1988, whereas in 1989 a couple of White Storks (Ciconia ciconia)built a nest near Dignano. The winter of 1985 was memorable for eleven specimens of the WhooperSwan (Cygnus cygnus), coming from the distant tundra marshes and waiting for milder climate, wereobserved further downstream, in the proximity of Camino al Tagliamento.

MammalsA long time ago, some of the mammals typical of the Friulian plain, such as the Common Hare (Lepuseuropaeus), the Red Fox (Vulpes vulpes) and the Beech-marten (Martes foina) were quite widespread. Today,they are often confined to the few remaining unspoilt environments such as the shingle and thefloodplain of the Tagliamento River, as their natural habitat is gradually disappearing. In fact, the RedFox regularly reproduces itself along the main riverbeds of the Friulian plain. Just like the Red Fox andthe Beech-marten, the Common Weasel (Mustela vulgaris) is another very useful scavenging mammal.The Badger (Meles meles), which is a difficult animal difficult to observe due to its nocturnal habits, isstable only in the flood forests of the Tagliamento, the Isonzo and the Torre rivers, however, today it issporadically found in the high and low plain. The Polecat (Mustela putorius) feeds on amphibians and canbe found especially in humid areas found in the floodplains, where it took refuge after it disappearedfrom most of the region due to land rearrangement and reclamation works. Finally, it is worth notingthat despite the Otter (Lutra lutra) is no longer found in the regional fauna, the middle course of theTagliamento River is considered as one of the few river corridors in the region capable of hosting it.

CONSERVATION AREAS IN THE LOW COURSE OF THE TAGLIAMENTO RIVER

Further downstream, close to the low rivercourse, there is another Site of Community Importance(SCI) called Bosco di Golena del Torreano33 (Wood of the floodplain of Torreano), one of the fewexamples of riverbed stretch and floodplain of the torrential rivers of the Friulian plain. Here, some ofthe best specimens of riparian forest with the Alnus incana and the Salix eleagnos being the dominantspecies, birds of prey (including nesting birds such as the Black kite and the Red-backed Shrike) and theAgile Frog can be found.Although the humid areas of the low plain do not strictly belong to the corridor of the TagliamentoRiver, they are undoubtedly connected with it due to the groundwater upwelling phenomenon. These 33 Code IT3320030.

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include very important conservation areas such as the Risorgive dello Stella (Stella GroundwaterUpwellings), the Risorgive di Zarnicco (Zarnicco Groundwater Upwellings), Risorgive di Flambro(Flambro Groundwater Upwellings) and Risorgive di Virco (Virco Groundwater Upwellings)biotopes as well as the Riserva Naturale delle Foci dello Stella (Stella River Mouth NaturalReserve).The Pineta di Lignano34 (Pinewood of Lignano) and the Foce del Tagliamento e valli arginate diBibione35 (Mouth of the Tagliamento River and embanked Valleys of Bibione), both Sites ofCommunity Importance (SCIs), represent one of the few remaining strips of a vast system of duneswithin humid areas. As far as the vegetation is concerned, “de-alpined” Alpine species, such as theAustrian pine (Pinus nigra), strangely coexist with Mediterranean species such as Phyllirea angustifolia,which has here its only regional station. The dunes bound by the herbaceous vegetation host the rareand endemic Stipa veneta, whereas one of the only two populations of Salix rosmarinifolia can be observedin interdune areas (the former can be found in the previously mentioned Torbiera di Curiedi).Among the reptiles, the Gecko Tarentola mauritanica, which was probably introduced, has now becomestable and reproduces itself.The area of the Tagliamento River is extremely vulnerable especially due to the high degree ofanthropization of the surrounding areas.

The entire corridor of the Tagliamento River, from the Lake of Cornino up to the downstream areapast the village of Pertegada, was classified as an Area di Rilevante Interesse Ambientale - ARIA(Area of Great Environmental Interest)36 as proof of the recognized need to introduce all-embracingconservation measures aimed at protecting the river corridor in its entirety and continuity, rather thantargeting isolated issues.

FINAL CONSIDERATIONS

In conclusion, the whole corridor of the Tagliamento River has features, which are unique to the entirepanorama of Alpine watercourses. It is its relative continuity, intended as the absence of discontinuitycaused by anthropic actions and impacts, which characterizes it throughout its flow, keeps alive acomplex network of mechanisms and ecological connections shaping an ecosystem which, as far asnaturalness is concerned, has no equal. This is especially true for the middle course of the river, asmany mountainous areas are stressed by water withdrawals for hydroelectric power generationpurposes and industrial pollution, whereas the lower course of the river has now become a mereartificial canal.In particular, the hypothesized construction of three detention basins to increase the floodcapacity of the river to cater for 100-year floods in the reach between Pinzano and Spilimbergowould affect one of the most delicate and valuable areas for the preservation of the ecologicalequilibrium, with hardly predictable and investigated consequences. In fact, areas, which arefundamental for the biology of a great many animal species, are at risk. For example, this stretch is veryimportant for the migration and reproduction of ichthyic species such as the salmonoids and thecyprinids, it is a safe shelter and an ideal habitat for the reproduction of many amphibians, whichappreciate quiet floodplain areas difficult to find in other parts of the territory, and it is also a migratorycorridor for many bird species. If the safety measures planned for the lowland areas were carried outfurther downstream, near the areas to be safeguarded, they would affect a territory which is alreadyheavily anthropized and which, as such, has already lost the typical features of the middle course of theriver and, therefore, it would not be affected by significant environmental impacts.It has been clearly demonstrated that a high degree of naturalness and biodiversity preservationrepresents also one of the best ways to guarantee hydraulic safety. In fact, the construction ofartificial embankments, where the river maintains its hydrologic equilibrium, reduces the river natural

34 Code IT3320038.35 Code IT3250014, site present in the Veneto region.36 ARIA no.8, further to the Regional Presidential Decree of 17 May 2002, no.0143/Pres, according to the Regional Law 42/1996.

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expansion area and increases the quantity of energy released by the flood wave towards anydownstream reaches. This increase in energy is matched by an increase in the erosion power of thewatercourse, disturbing the erosion - debris transport - sedimentation equilibrium. A number ofconsiderations seem to confirm that the demarcation line, which separates the island-braidedstretch and related gravel bed from the meandering stretch, is relentlessly but continuouslyshifting closer to the sea37. This process started when the first embankments were built in thenineteenth century and it is due to the higher erosion power of the Tagliamento River in itsmiddle-high course, thus increasing the quantity of material, which eventually deposits in theplains. Theoretically, the forward movement of the gravel bed could extend down to the sea. This hasalready happened with other rivers and may have adverse consequences for human settlements situatedin this stretch.Vegetation growing within the riverbed of the Tagliamento plays a fundamental role and islinked to precise balances and dynamics. The frequent floods occurring within the corridor aresuch that the ecological sequence is continuously perturbed back to an early stage of development,thus, to some sort of herbaceous-shrubby vegetation thereby reducing the presence of arborealvegetation within the riverbed. As a result, the speed of the flood wave is mitigated, its energy“spreads” over a wide and diversified area, and erosion decreases making way to silting. On the otherhand, the regulation and the optimization of the regime of those reaches, characterized by ahigh degree of naturalness, leads inevitably to a disruption in their equilibrium, denying theriverbed environment the importance it deserves and “dumping” most the solid silt furtherdownstream, hence increasing the speed of the water discharge with more and more frequentdramatic consequences for the riparian populations.

Therefore, under normal conditions, a watercourse reaches the equilibrium which induces a certaindegree of safety, unlike other anthropic actions, which do not provide solutions and often shiftproblems somewhere else, making them worse and disrupting situations of vital equilibrium. Finally, itis worth noting that every watercourse has shaped its own corridor over the centuries accordingto its complex features and, any modification aimed at disrupting this equilibrium will unchaina system reaction that will attempt to bring it back to its original state.

Fig. 15 Vegetated islands and island-braided reaches of the Tagliamento River (Photo by Toni Vorauer, WWFAustria) 37 Spaliviero, M. (2002) Historic fluvial development of the Alpine-foreland Tagliamento River, Italy, and consequences for floodplain management.Geomorphology 1277 (2002) 1-17

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ECONOMICAL AND COMMUNITY IMPACT ANALYSIS

ANALYSIS SET UP

The scope of the economical and community impact analysis is to compare alternative projectproposals aimed at tempering the flood peak of the Tagliamento through the construction of detentionreservoirs in the riverbed in order to increase its flood capacity.Accordingly, two hypotheses were formulated and analysed as follows:- The Abridged plan for the hydraulic safety of the territory put forward by the Basin Authority for

the North Adriatic Rivers; and- The alternative proposal to increase the flood capacity of the lower and middle reaches of the

Tagliamento River developed by the workgroup coordinated by Prof. Todini.

The above action proposals were evaluated against the No-action alternative, which assumes that theexisting situation remains basically unchanged.

The analysis is structured around the following main areas:a) Definition of the evaluation methodology;b) Description of the status quo and of alternative project proposals;c) Identification of flood-prone areas which may be affected by damages and by the various actions

planned;d) Description of the various scenarios and definition of the evaluation criteria;e) Cost-benefit assessment;f) Census taken of stakeholders followed by the identification and evaluation of the potential impact

on each subject category;g) A brief synopsis on the evaluation of the various alternatives.

The conclusive part includes a set of considerations on the work carried out, strategic indications onhow to tackle the next steps of the process and operational indications on how to handle themanagement of the various actions undertaken.

EVALUATION METHODS

The primary goal of any ex-ante evaluation process is to identify the changes caused by an action(policy, programme, project) on a system and then gives a brief overview of these changes in order toprovide a useful support to the decision-making process.The evaluation tools differ depending on the type of actions under examination, but also on the values(and related criteria) considered useful for the choice.The analysis has been carried out using an economic approach: the objective was to identify the costsand benefits accruing under each of the solutions considered in order to provide a knowledge base anda number of significant interpretation elements for the evaluation. To achieve this, it will be necessaryto establish the current degree of risk and that which is envisaged to apply after the actions have beentaken but also to identify the most convenient and practical alternative.

In this particular case, a Cost/Benefit Analysis (CBA) approach was used. In its classic form, thismethodology takes into consideration the costs and benefits accruing to a system after an action hasbeen taken, it measures them in monetary terms and attempts to provide a brief evaluation of theirrelationship using only one indicator. This type of analysis is very effective when the values at stake aremainly economical, the community is quite heterogeneous and its level of interest is sufficientlyuniform. This is certainly not the case with the actions planned for the Tagliamento River, where socialand environmental costs as well as benefits are important and their distribution is not uniform due tothe fact that some social sectors and/or entire communities are affected either by costs or benefits.

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This is the reason why this study was developed through two complementary analyses:1. the verification of the economical advantage of the actions

Despite the uncertainty associated with the basic information available, it was believed importantto carry out an analysis of the costs of the actions and a comparison of this analysis with theexpected benefits. The economical-financial analysis was performed by applying the Net PresentValue (NPV) criterion and the Cost/Benefit (C/B) ratio.

2. Community Impact AnalysisThe objective of the Community Impact Analysis is to integrate the economical-financial analysisso that also the following elements are taken into account:- any non-monetizable impacts due to lack of market values;- the distribution of costs and benefits for the various categories of actors involved.By relying on a method which borrows from the Economics of PlannedDevelopment/Community Impact Analysis (Lichfield, 1996) it is possible to break down thepossible welfare changes for the main territorial and social categories.This entails the processing of matrices which are less “elegant” than the traditional aggregatedCost Benefit Analysis (CBA), but capable of better recording all the effects and impacts from allpoints of view (areas, social groups, etc.).In addition, the analysis allows an assessment of the hypotheses based on a possible negotiationbetween the “actors” involved and the creation of a series of alternative or supplementary ideas,which may contribute to guide the decision-making process towards better solutions with a viewto sustainable development.

STATUS QUO AND ALTERNATIVE PROJECTS

Two action hypotheses were examined, however, although they are not the only possible actionsavailable to attenuate the flood peak, they represent the only developed proposals with project content,which enable them to be compared in a C/B type analysis. These hypotheses were compared with theexisting situation or No-action alternative.The main simplifications made to facilitate such comparison are as follows:- the actions envisaged by the Abridged Plan with regard to the lower reaches of the Tagliamento

(either already in the pipeline or planned for the future) were considered only at a descriptive level;the financial and community impact analysis was performed solely with respect to specific workscarried out to increase the flood capacity of the river. Thus, the assumption made is that all workshave been completed and that at Latisana the discharge is equal to 4000 m3/s. This choice is linkedto a number of factors: the difficulty in establishing the contributions made by each project to thehydraulic safety, the centrality of the retention basins from a functional point of view (reduction ofthe discharge at Latisana from 4600 to 4000 m3/s) and in the debate currently under way;

- to calculate the cost of the various actions and their related benefits it was assumed that serviceswould be delivered as soon as the construction works commenced. This simplification avoids havingto rely on a cost-time chart, which with this type of works is actually difficult to comply with, and onthe calculation of the partial benefits, which could be obtained while the works are in progress; and

- the estimate did not take into account any health damage or loss of human lives. In the authors’opinion, safeguarding these values cannot be considered “negotiable” nor can it be estimated inmonetary terms38. Moreover, as already indicated, non-structural measures are those, which bestguarantee the safeguard of population. As these actions can be initiated within a relatively shortperiod of time and require small capital outlays, it is assumed that these measures are in place.

38 Generally C/B analyses resort to estimates of the value of human life, linked to any income, which may accrue in the future, and any biological damagesin terms of lost income as well as care and assistance costs.

41

a) No-action alternativeThe no-action alternative is the present situation, which assuming no actions are taken, wouldremain unaffected by major changes over time. This is a no-action solution that, althoughunanimously excluded, remains to date the winning choice. It represents the reference hypothesisfor the assessment of the proposals to carry out works to increase the flood capacity of the river.

b) Abridged plan for the safety measures set out by the Water AuthorityOn 28 August 2000, the Abridged plan for the hydraulic safety of the middle and lower reachesof the Tagliamento River was approved by a Decree issued by the President of the Council ofMinisters (Official Gazette no.69 of 23 March 2001), which may be viewed as the result of a longtechnical, administrative and political process, started after the flood events which occurred in themid-60s. This is an abridged plan, i.e. the identification of a number of projects deemed usefulfor a specific goal, which is the hydraulic safety of the lower reaches of the river due to the lackof a real Basin Plan.39

The abridged plan entails actions to mitigate the flood wave in the middle course of theTagliamento and to increase the overflow capacity (discharge) in the final stretch of the river. Thesuggested hydraulic scheme is as follows:- at Latisana, the maximum discharge of the Tagliamento must not exceed 4000 m3/s;

downstream of Latisana, 1500-1600 m3/s of the discharge will flow into the Tagliamento and2400-2500 m3/s will be diverted into the Cavrato channel which needs to start operating whenthe flow exceeds 1500 m3/s as opposed to the actual 900-1000 m3/s;

- any excess water will need to be temporarily retained in appropriate detention basins,constructed in the middle course of the river, downstream of the Pinzano gorge, having a totalstorage capacity of 30 million m3.

The reference event taken into consideration to establish the extent of the works is a 100-yearflood.The works envisaged by the plan are included in the table below and are ranked according to thepriority level assigned to them by the abovementioned document:

Priority Abridged plan

1 - improvement and strengthening of the embankments through aprons (Cesarolo)2 - first water retention basin downstream of Pinzano (approx. 10 million m 3)3 - intake construction of the Cavrato channel4 - structural adjustment of the Cavrato drainage channel5 - second water retention basin downstream of Pinzano (approx. 10 million m 3)6 - adjustment and strengthening of the dikes of the final stretch of the Tagliamento,

from the intake of the Cavrato up to the mouth7 - third water retention basin downstream of Pinzano (approx. 10 million m 3)8 - completion of apron and defence works downstream of Ronchis

Three water retention basins are planned to be carried out in the middle part, with the aim ofdecreasing water discharges with flood waves greater than 4000 m3/s. In the outline hypothesis,the water retention basins are considered as three storage basins and, the related channelizationworks carried out near the right bank of the river reduce the width of the riverbed from 2.5 kmto 0.8 km approximately.

39 The Abridged plan does not include elements, which define it as a real plan, however it has all the features of a project meant to be carried out in phases.In fact, it deals only with the execution of a number of construction works, lacking the predictions required to spread integrated actions throughout theentire basin and the territory crossed by the river.

42

In order to start the implementation phase, the Region has issued a call for tenders for thepreliminary planning of the works. This phase of the administrative procedure is stillincomplete, as the list of the winners has not yet been published40.

c) Alternative hypothesis to improve the flood capacity of the middle and lower course ofthe riverTaking into account the reference parameters set out in the Abridged plan, the objective here isto attenuate the flood wave through actions which try to avoid interfering, as far as possible,with the natural equilibrium of the river and preserve the middle floodplain tract which is anarea of high environmental value and the chosen site for the construction of the reservoirsenvisaged by the Abridged plan.The action proposals entail:- raising of the embankments on the orographic right side by 1 metre41;- re-elevation and reinforcing of the sections south of Latisana, located before and after theCavrato channel,- the construction of seven retention basins in a stretch of approximately 20 km, betweensection no. 129 and section no. 80, to the north of Latisana having a storage capacity of 21million m³.These areas are located within the main river right and left embankments, which require theraising of the floodplain banks over a stretch of 24 km, as well as protection works to be carriedout at the toe of the embankment. In order to ensure the proper operation of the overflowthreshold, three open weirs are planned to be constructed to serve the first five retention basinswhich will neither interfere with low and moderate discharges, nor with the water in both theunderflow conduit and the water table.

The study highlights the fact that the railway bridge in the Latisana bottleneck may represent anobstacle as it lies one metre below the height of the embankment, and also that there is thepossibility of increasing the average discharge to 4000 m3/s if the planned construction worksto raise the bridge are carried out.

Priority Hypothesis of increasing the flood capacity of the riverin its middle and lower course

1 - superelevate the railway bridge at Latisana- raising of the embankments between section no.146 and section

no.1452 - structural adjustment of the Cavrato drainage channel

- intake construction of the Cavrato channel- raising and reinforcing of the sections situated before and afterthe Cavrato channel

3 - construction of the first two water retention basins (sections130/124, approx. 6.6 million m3)

4 - construction of the third water retention basin (sections 124/118,approx. 3.9 million m3)

5 - construction of the fourth and fifth water retention basins(sections 114/107, approx. 7.8 million m3)

6 - construction of the sixth and seventh water retention basins(sections 85/76 and 82/78, approx. 2.7 million m3)

40 The description of the planned actions does not take into account the working drawings, recently released by the Regional Authority, as the execution ofthe works might be substantially different from the one envisaged by the four selected working drawings, as required by the tender rules.41 Corresponding to sections no.146 and no.145 of the Barigazzi survey, located at 70,435 and 69,835 metres from the sea respectively.

43

IDENTIFICATION OF AREAS CONCERNED

In order to estimate a correct cost-benefit ratio it is necessary to define the risk-prone territory, theextent and frequency of damage as well as the areas affected and the modifications caused by theactions envisaged in the hypotheses.

a) To identify the potentially flooded area and the extent of the damage, reference was made to therisk-prone zoning42 prepared by the Basin Authority for the North Adriatic Rivers in compliancewith Law No. 267 of 1998 (the so-called Sarno Law). This zoning identifies three levels of risk, eachof which is related to a specific water blades in case of a 100-year flood event: P1 = up to 50 cm; P2up to 1 m; P3 up to 3 m. The surface of the affected areas has been worked out based on thecartography maps (CTR- Regional Technical Maps) at a scale of 1:10,000 distinguishing for each Plevel any urban areas, scattered houses and agricultural lands or similar areas.The total flood-prone area is equal to approximately 12,500 ha and falls within the Municipalities ofVarmo, Ronchis, Latisana, Lignano, Morsano al Tagliamento and San Michele al Tagliamento43.The area is represented mostly by agricultural land, only 8% being covered by residential buildingsor production plants.More than 70% of the territory is hit by less than 50 cm water blade, whereas 5.4% is affected by aflood ranging between 1 and 3 metres. The extent of the damage is undoubtedly affected by thepresence of hundreds of urban settlements with a high concentration of valuable propertyrepresented by portions of the historical centres of the towns of Latisana and San Michele alTagliamento.The population living in the flooded area is estimated to be approximately 20-25 thousand people.

Affected surface

(ha)

P1 P2 P3Total

Percentage

values

Centres and settlements 524 115 98 737 5.9

Scattered houses 199 9 28 236 1.9Cultivated area 8,328 2,708 558 11,594 92.3

Total 9,051 2,832 684 12,567 100

Percentage values 72.0 22.5 5.4 100

In addition to the abovementioned areas, which are directly affected, also the area near the mouthof the river should be taken into consideration as many kilometres of shoreline are affected by theaccumulation of debris transported by the flood.

b) The area which is directly affected by the construction of the water retention basins envisaged bythe Abridged plan is represented by a floodplain situated on the right bank of the Tagliamento, thetotal surface of which amounts to approximately 1,100 ha. The area devoted to agricultural crops isapproximately 650 ha, whilst the remaining 481 ha are not cultivated. Assuming the crop allocationreported by the latest 2000 General Agricultural Census conducted by ISTAT (Italian NationalInstitute of Statistics) in the neighbouring municipalities, it could be estimated that the area wouldbe used as follows: 327 ha of fit for seed-lands, 226 ha of permanent crops, 58 ha of meadows, 9 haof poplar plantations, 30 ha of wood and forest land. The effect on the agricultural uses is related tothe damage resulting from the filling of the basins as well as to the disruptions and permanentmodifications of the waterbed. The narrowing of the riverbed will affect fish farming activities

42 As the zoning document has not yet been released to the public, inspection was only possible at the offices of the Regional Spatial Planning Directorate.43 According to a communication by Prof. Marco Petti of the University of Udine (CIRM Seminar, Udine, 30 April 2003), by applying an innovativehydraulic model to the basic data available (an accurate verification revealed them as being incomplete), overflowing occurs in four points, three of whichtake place between Ronchis and Latisanotta, and one just next to the railway bridge of Latisana. This hypothesis provides a better definition of theboundaries of an area exposed to a greater hydro-geologic risk. This area, which comprises largely of new surfaces, is made up of farmlands and smallsettlements and is affected by a moderate water blade. In this scenario, the percentage of damages would be 20-25% greater than the one calculated underthe “Sarno” hypothesis.

44

currently practised on the left bank of the river within the Municipality of San Daniele del Friuli. Infact, as the river discharges flow in a lower section, they significantly modify the hydrometric level,which may often reach heights, which are incompatible with the existing bypass system.

c) The seven detention reservoirs envisaged by the alternative hypothesis affect an area which issimilar, in terms of size, to the one considered by the Abridged plan, i.e. approximately 1,050 ha. Ofthese, 600 ha and 468 ha are allocated to cultivated and non-cultivated areas respectively. Assumingthe crop allocation reported by the latest General Agricultural Census for the Municipalities ofRonchis and Varmo, the following values are obtained: 544 ha of land fit for seed, 10 ha ofpermanent crops, 11 ha of meadows, 14 ha of poplar plantations, 17 ha of wood and forest land.Quarry activities such as extraction, selection and washing are carried out in the uncultivated area.For these activities the level of risk would be probably similar to the one they are exposed to atpresent, even if flood frequency may increase. The area is already subject to floods andarrangements are in place to ensure the moving of equipment by taking into account the potentialwater levels. Fixed assets, represented by buildings, oil mills, sieves, concreting stations for quarryactivities, washing, selection, possible production of pre-parcelled concrete, cannot be locatedwithin the dikes, or rather it is advisable that, in case they are, they be moved to appropriate D4zones. Any muddy materials, which might deposit in the basins, have the same particle-size as thefine sand of the Tagliamento and therefore could be treated as such.

DESCRIPTION OF SCENARIOS AND DEFINITION OF EVALUATION CRITERIA

The comparison between the three hypotheses leads to the definition of three different scenarios:- Leaving the present situation unchanged;- The construction of the works envisaged by the Abridged plan, hence solving the 100-year event

risk and achieving the partial mitigation of events with a return time greater than 100-years;- The construction of the works envisaged by the alternative proposal, hence solving the 100-year

event risk and achieving a limited mitigation of events with a return time greater than 100 years44.

These scenarios entail financial costs and benefits, which must be estimated.Under the hypothesis of leaving the present situation unchanged, with actions being carried out, thecost sustained by the community as a whole is equal to the net present value of all the potentialdamages added together:- direct, private and public material damages;- private and public indirect damages;- limitations of use; and- infrastructural and environmental damages which can be measured in monetary terms.In case the water retention basins and other hydraulic works are carried out, against benefits to beestimated on the basis of the frequency and magnitude of the avoided damages, the analysis of the costswill need to consider:- the cost of carrying out the works (construction of the detention basins, strengthening of the basin

side wall, possible adjustments made to the low flow channel (riverbed) located downstream)including all construction site costs45;

- basin maintenance costs;- lost revenue.

Each hypothesis uses a specific method to evaluate these economical and financial aspects, as theircharacteristics and in particular their information basis differ.

44 The lower capacity of the detention basins envisaged by the alternative proposal led to estimate a contribution to the mitigation of floods with a returnperiod greater than 100 years, lower than that offered by the Abridged Plan (see note 54).45 Reconditioning costs were not taken into account as it was assumed that the effect of the actions might be continuous and for an indefinite period oftime (dismantling of the structural works as well as removal and disposal management of debris)

45

a) No-action alternative

Damages were assessed based on the simulation of the effects of a 100-year flood event.An estimate of the losses per surface unit was calculated for each type of land use and risk area.These estimates were arrived at by using data of floods of various magnitudes and intensity that haverecently occurred in the Municipalities of Lestizza (1998) and Pordenone (2002), both in Friuli VeneziaGiulia, which have been appropriately tailored to suit the case under examination.In particular:

1. built-up areasWith regard to the territory occupied by buildings, (centres, settlements and scattered houses):- with water blade up to 50 cm – from 0 to 50 cm - (P1) reference was made to the flood of the

Cormor brook, which affected the Chief town as well as the Santa Maria hamlet, and themunicipality of Lestizza46. The documentation (number of damage claims, criteria for thecalculation of the damage indemnities and related payments) provided by the Technical officeof the Municipality of Lestizza represented the basic information used as a starting point. Theofficial data were integrated in order to take into consideration all those elements, which arenot recognised by public action (in terms of both criteria and financial constraints).

- With water blade up to 1 m – from 50 cm to 1 m – (P2) reference was made to the flood,which affected the northeastern part of the town of Pordenone in November 2002. The basicdata were provided by the Technical office of the Municipality of Pordenone (these includedthe list of the damage claims, the criteria adopted to establish entitlement and the mapshowing the flooded areas as per the Town Council resolution no.130/02). Also in this case,all the damage elements, which had not been recognised by the indemnity prearranged by thepublic body, were considered.

- With regard to a water level limit up to 3 m – from 1 m to 3 m – (P3) the conditions andrelated values obtained for the P2 risk scale were considered to have worsened andconsideration was given to the presence of traditional and historical buildings, as well as to theconcentration of high-value tertiary activities in the area exposed to such risk. The three-metrewater limit was considered as the maximum, by taking into account that the water level wouldaffect only the first floor and that the upper floors would not be directly damaged.

2. farmlandIn this case the damage is linked to:- crops currently cultivated (species and varieties, crop cycle phase, average yield);- agricultural characteristics of the land and the presence of agricultural infrastructures and

irrigation systems;- water level;- the time water stays.The distribution of crops was made on the basis of the data of the latest 2000 AgriculturalCensus conducted by ISTAT for the affected municipalities, as it was reckoned thatapproximation would be sufficient to define the extent of the damage.The weighted average of the damages that can be surmised for each main category of crops wascalculated using the above elements. The maximum damage value is represented by the loss ofthe fruit still on the plant (hanging) at the time of harvesting (the expected value of the harvestless costs incurred for the harvesting). This value was reviewed to consider the non-simultaneityof the crops and it was increased for the costs relating to the restoration of the originalagronomic conditions, considering that the water stays for approximately one week.

46 This flood gave rise to situations similar to those with a 50 cm high average water blade with peaks, which in the Santa Maria hamlet reached and evenslightly exceeded 1 metre.

46

With regard to the P3 and P2 zones, the values obtained were considered as the average damageper surface hectare. In the P1 zone, considering the modest impact of the expected water level,the damage was estimated to be equal to 20% of the value calculated for the other two zones.The calculations did not take into account cattle-farms, which, on the other hand are littlewidespread in the territory under examination, as their safety can be achieved using simplepreventive measures.Agricultural buildings were considered under damages suffered by built-up areas.

3. Territorial infrastructuresOn the basis of recent surveys and analyses performed for the drafting of the PRGC incomparable areas, the development of territorial, road and railway infrastructures can be assumedto be equal to 2.5% of the total surface. The damage for this type of immovable property can beestimated as follows:- P3 zone: settlement of the roadbed, scarification of the tar mix, resurfacing the roads with

bitumen coating (binder and blanket), housing minor works of art; cleaning and restoration ofdrainage ditches and road signs; as regards railway lines, settlement of the ballast, of the floorsystem and the railway track and structures;

- P2 zone: to an extent equal to two-thirds of the damage suffered by the P3 zone;- P1 zone: approximately equal to 20% of the damage suffered by the P3 zone.

4. ancillary operational costsThe flood-prone area is crossed by a network of infrastructures of regional, national andinternational importance. With regard to this significant aspect, taking into account the flatterritory, with a slight and uniform north-south acclivity, as well as the localisation and size of theP1, P2 and P3 zones, it is possible to formulate the following hypothesis:- the motorway and the railway are not significantly affected (the network will not be closed to

traffic) thanks to the elevation of their respective construction works. The only criticalsituation is connected with the possible temporary raising of the iron railway bridge at Latisanaand, hence the interruption of the line for a few hours. As the bridge underbeam is at a lowerlevel than that of the embankment, the above action must be planned and it may even becomenecessary in case of a flood, even if works for the detention basins are carried out;

- as regards highways, the bridge on highway no.14, which crosses the Tagliamento at Latisana,should be closed to traffic. Interregional traffic could use alternative routes such as themotorway or other roads (less smooth, but acceptable considering that the bridge would beclosed for a short period of time) at less than ten kilometres to the north as the crow’s flies(Madrisio bridge on the Provincial Road no.95) and at 10/15 km to the south (Bevazzana).

- the provincial network does not suffer from interruptions at Lignano and Bibione. Inparticular, the Madrisio Provincial Road no.95 (made on an embankment which had originallybeen planned for a railway) runs at a safe level; the Provincial road no.75 which connects theHighway no.14 with Lignano, represents the eastern limit of the P1 zone; to the west, in theVeneto region, the P1 zone is bound by the road which skirts the “Taglio Nuovo” channel atless than 3 km from S.Michele al Tagliamento; also immediately close to the north, the P1border is represented by a road constructed on a shallow earth embankment;

- the network of local roads which fall under the P2 and the P3 zones relates to an area which isin the immediate neighbouring of the Tagliamento and the Cavrato channel:

- the period of time during which the water stays thus preventing traffic from flowing or in anycase causing discomfort in the P1 zone should not exceed 24/48 hours. The extent of erosionor damage caused by water in the P1 zone is not such to require subsequent closing of theroads to traffic;

- the tourist sector, quite widespread in the neighbouring shoreline area, should not suffer eitherfrom direct or indirect damages due to floods;

47

The costs, which the Government would incur as a consequence of the above situation, are noteasily quantifiable, but it is assumed that they would range between 5% and 15% of the amountof the structural damage, moving from the P1 to the P3 zone.In addition to the above costs, there are indirect costs, relating to the restoration of originalconditions, equal to approximately 10%.

5. general and emergency costsIn order to assess general and emergency management costs, estimates were made starting fromthe analysed incidents and then they were compared with the final results of the most severenatural calamity which occurred in the Friuli Venezia Giulia region in the past century, theearthquake of 1976. Also in this case, a prudent estimate leads to values ranging between 5% and15% of the amount of the structural damage, moving from the P1 to the P3 zone.

b) Abridged plan hypothesis

The cost of the works for the detention basin envisaged by the Abridged plan is stated in the documentitself, and amounts to 150 billion lire, VAT included (equal to approximately 77.47 million euros) withno details being provided. The above figure was used for the evaluation47.In order to compare the various action hypotheses, more significant physical quantities were used froman economical and environmental point of view. With regard to the water retention basins of theAbridged plan, this was possible by using the information contained in the only project, among theones, which had been submitted to the call for tenders, for which an approximate calculation wasavailable48.The categories being considered are:- excavations;- embankments;- coarse pumice aggregate for concrete;- cement- rockfill dam;- iron for reinforced concrete and steel in general;

Action Excavation Embankment Pumice for

reinforced concrete

Cement Rockfill dam Iron for reinforced

concrete and other

Area occupied by

the basins (ha)

1 Abridged plan 2,278,435 2,226,203 82,091 204,141 53,381 6,403,891 1,112

2 Alternative

hypothesis

382,064 1,198,676 58,109 143,731 64,097 7,087,426 1,063

Difference (1-2) 1,896,371 1,027,527 23,982 60,409 - 10,716 - 683,535 49

c) Alternative hypothesis for the increase of the flood capacity of the middle and lower reachesThe action on the middle and lower reaches envisages the construction of seven water retentionbasins and three open weirs, capable of making the water surge and the basins fill, situated in adifferent location from the one stated in the Abridged plan.The cost estimates were made by unit indexes, starting from a comparison with similar works. Theonly scope of solutions considered, which were judged as rational from a technical and economicalpoint of view, is to allow an estimate of the costs. Also in this case, in fact, the elements at hand arenot enough to allow an approximate estimate, but can only help to establish a relative order of sizeuseful to carry out an ex-ante valuation of different strategic options.

47 The call for tenders for the final planning of the project quoted a maximum amount of 200 billion lire (103.3 million euros). Three of the four bidsselected for evaluation range between 140 and 155 billion lire (72.30 – 80.10 million euros).48 Hydrodata project. The other projects admitted – Technical, SWS and RPA – could have values which differ substantially from the one used as theydepend on the technical choices respectively adopted. Nevertheless, the order of size of the project volumes for the major hydraulic works (designed takinginto account soil morphology and functions required) should remain basically unaltered.

48

The estimated cost of the weirs was based on technical and economical data of recently draftedprojects relating to the construction of very big viaducts (works which, as regards the constructiontype, may be compared to the weirs), recently envisaged to be carried out in the region. Inparticular, a four-lane viaduct of approximately 250 m was used as a reference point for extractingthe cost indices, which were then applied to the length of the weirs envisaged by the project underreview. In particular, the part which was taken into account was the floor system which supportstwo lanes, whose estimated cost was translated from the original four-lane project by applying acoefficient of 0.40 for the 3 m h x 1200 m l weir; by applying a coefficient of 0.50 for the 3.90 m hx 900 m l weir and by applying a coefficient of 0.60 for the 6 m h x 600 m l weir.

The internal embankments required for the carrying out of the water retention basins were planned tohave a pebble gravel foundation 1 metre below the average land-surface, a 45% bank slope and rockfillcover for 50% of that part of the embankments exposed to the current and for the overflow sill. Onthis overflow sill, the revetment is planned to be cemented with concrete in a quantity equal to 25% ofthe volume of the revetment itself.

As regards the raising of the existing floodplain embankments, it is planned to maintain the present45% bank slope and the 3-metre width at the top, to remove the turf on the surfaces affected by theworks and to restore it on the new parts. Considering that the embankments will need to be onlyslightly raised (except for a limited number of stretches) no concrete baffle plates, nor foundationsdifferent from the ones already indicated are envisaged.

In addition to the above-calculated costs, 20% of overheads were added to compensate for normaltechnical expenses relating to design, management, testing, temporary structures and any reclamation ofthe affected areas. Italian VAT applied to the works was 20%49.

EVALUATION OF COSTS AND BENEFITS

By applying the abovementioned methodology, it is possible to quantify the costs and benefits, whichmay be expressed in monetary terms.In the hypothesis of a flood with a 100-year probability of occurrence, as defined on the basis of thezoning for the “Sarno” law, damages may be quantified as amounting to 220 million euros.

P1 P2 P3

Centres and settlements 19.65 26.19 58.64 104.48

Scattered houses 7.50 2.05 16.75 24.34

Farmland 3.45 3.74 0.77 7.97

Infrastructures 6.79 10.62 9.40 26.81

Total 37.39 40.64 85.56 163.59

Indirect costs 5.37 6.74 22.61 34.72

Emergency costs 1.79 4.49 13.56 19.85

Total 44.55 51.87 121.73 218.16

A more dramatic hypothesis may occur due to an increase of the affected surfaces or to anembankment failure in an urban area. The second possibility is undoubtedly the one with the highestimpact on the economic damage due to the increase in the P3 zone values. These hypotheses were notexamined under the present study as they were considered as falling outside the indicated decision-making context, but they may be evaluated at a later time by applying the processed unit values.

49 All goods and services have been calculated gross of Italian VAT, i.e. at market price, using a C/B analysis.

49

The overall cost of the works to increase the flood capacity of the river envisaged by the Abridged planis estimated to be 165.27 million euros (Italian VAT included).

Priority Abridged plan Costs (million euros)1 - improvement and strengthening of the embankments through aprons (Cesarolo) 20.662 - first water retention basin downstream of Pinzano (approx. 10 million m 3) 37.183 - intake construction of the Cavrato channel 25.824 - structural adjustment of the Cavrato drainage channel 15.495 - second water retention basin downstream of Pinzano (approx.10 million m 3) 20.666 -adjustment and strengthening of the dikes in the final stretch of the Tagliamento,

from the Cavrato intake up to the mouth10.33

7 third water retention basin downstream of Pinzano (approx.10 million m 3) 19.638 - completion of apron and defence works downstream of Ronchis 15.49

TOTAL 165.27

The cost of the adjustment works of the Tagliamento in the stretch from Latisana to the mouth and ofthe Cavrato channel, amount to less than total costs, whereas the cost of the detention basins amountsto 77.47 million euros, analysed as follows:

Abridged plan Costs (million euros) - first water retention basin downstream of Pinzano (approx.10 million m 3) 37.18 - second water retention basin downstream of Pinzano (up to a storage capacity of 20 million m3) 20.66 - third water retention basin downstream of Pinzano (up to a storage capacity of 30 million m 3) 19.63TOTAL 77.47

The cost of the detention reservoirs of the alternative hypothesis may be calculated with an estimate ofunit values of approximately 36 million euros, analysed as follows in the five foreseen actions:

Action Works Raising of the

embankments

Internal

embankments

Weirs Total

water retention basin no.1 1.80 1.20water retention basin no.2 1.80 1.17

1

Weir 6.78 12.74

water retention basin no.3 1.45 0.962Weir 6.36 8.77

water retention basin no.4 1.27 1.03

water retention basin no.5 1.56 1.20

3

Weir 5.09 10.15

4 water retention basin no.6 1.87 0.96 2.82

5 water retention basin no.7 0.91 0.60 1.51

Total10.65 7.11 18.23 35.99

50

It is worth noting that the total cost to be incurred by those carrying out the works must also includeoverheads and Italian VAT, which for hydraulic works is 20%. This amount, which is now comparableto the one of the works envisaged by the Abridged plan, is equal to 50.39 million euros.

Costs (million euros) Cost of materialand works

Overheads(20%)

Italian VAT20%

Total

Raising of external embankments 10.65 2.13 2.13 14.92Construction of internal embankments 7.11 1.42 1.42 9.96Construction of weirs 18.23 3.65 3.65 25.52

TOTAL35.99 7.20 7.20 50.39

These figures take into account only the financial costs expected to be incurred to carry out the works.In addition to these costs, there are also management and maintenance costs as well as costs arisingwhen the works become operational:- in both actions aimed at reducing the flood discharge, slickens is a very relevant aspect and the

settled amount depends on the capacity of the water retention basins and the time taken by the latterto empty. Thus, in addition to the maintenance costs for the new embankments, there will also bethe cost related to the maintenance and cleaning of the water retention basins after the event. Theassumption that the first water retention basins will frequently fill up implies the need to plan forsites or alternative uses of large quantities of slickens. This study fails to examine this aspect in anydepth, however it may become significant and entail a possible increase in maintenance costs if theslickens needs to be disposed of, whereas if commercial use of the slickens is possible, thenmaintenance costs may be lower (mixing with fat soils for agrarian uses, grass sport fields orgardening);

- the two hypotheses involve the construction of new embankments and the raising of part of theexisting ones. This fact, which, pending more accurate calculations may be considered as having thesame impact in both cases, will result in an increase in management and ordinary maintenance costsequal to that required for approximately 34 ha of embankment surface50.

- as floods, with a lower discharge and no overflow increase in frequency, the yielding of theembankments as well as greater erosion due to the lack of “free” floodplain areas may occur. Theentity of these phenomena may become significant for the hypothesis of the Abridged plan, whereasthey appear to be less crucial for the alternative hypothesis. From an economical point of view, theeffect may be considered as an increase of the yearly maintenance costs.

Finally, the environmental effects, highlighted by the analysis carried out along with the economicalone, as well as any cultural effects are worth noting. The analysis does not attempt to quantify them inmonetary terms and to include them in the evaluation table, it simply points them out51.The construction works and the long-term consequences of the new fluvial dynamics envisaged byboth projects will have permanent and direct impacts on the landscape. In addition, in terms of visualamenity, there will be impacts on the ecosystems, due to the construction works (execution phase) andthe permanent modification of the environmental conditions, in particular the flow of deepwater andsurface water. In both cases, due to the size and location of the works (particularly highembankments and within the catchment of a Site of Community Importance (SCI), as definedin EU Habitat Directive 42/93), the hypothesis of the water retention basin in the area furthernorth proves to be more prejudicial compared with that which envisages the basins to beconstructed further downstream.

50 This maintenance relates mainly to the mowing and uprooting of shrublike and arboreal vegetation, where the embankment is not protected by bitumengrouted stone revetment.51 It is believed that the quantification of the environmental effects of these projects cannot be calculated without affecting the reliability of the overalljudgement. This economic analysis and the environmental one can however act as a reference point for a multicriteria evaluation of an environmentalimpact study.

51

As both hypotheses promote a further “artificialisation” of the watercourse, by erecting “barriers” andcreating limitations to the present use of the basin areas, from a cultural point of view, they encouragelocal communities to “distance themselves” from the river. In the case of the alternative hypothesis,this impact would be partially dampened by adding extra length to one of the weirs so that it could beused as a bridge, and therefore promote the interaction of the local population with the river andfacilitate the relationships among the communities living on the two banks.

IDENTIFICATION OF STAKEHOLDERS

Along with the calculation of the economic values at stake, another investigation was also conducted toidentify and define the actors which have a bearing on the decision-making process and which arenecessary to perform the community impact analysis. In particular, for each party, the following werehighlighted:- the relevant interests and their classification, depending on whether they were of economical-

financial nature or not and direct or indirect.- the location, as the same category of actors may have different interests and positions, depending,

for instance, on whether they are in areas with a critical hydraulic safety level or in the specific areawhere the detention basins are planned to be executed;

- the landmark of the potential impact, which guides the actors towards one or the other hypotheses;- the level of importance of the interest at stake, which influences the commitment of the party in the

decision-making process.The actors were grouped under three main headings (administrations, privates, general public), andeach of these headings was further subdivided based on interest similarity and social role.

a) Administrations and Public entitiesLocal administrations have a priority interest in the safety of the citizens and in the safeguard of theassets and income of their own communities: guaranteeing safety and healthiness to the population fallswithin the main tasks of the Municipality, whereas ensuring a good planning of the territory and of theroad infrastructure falls within the main tasks of the Province. These objectives legitimise the veryexistence of these entities and for this reason they are at the top of the political agenda of all thecouncils operating in territories exposed to hydrogeological risk52. This is the reason why non-economical and indirect economical interests are more important for the Municipalities and theProvince.For the Municipalities which show a protection deficit, the carrying out of works to improve theflood capacity of the river offers a direct economical benefit linked to the possibility of avoiding theloss or the diminution in value of owned assets and the reduction of the services provided. Althoughthis advantage may be less significant than for private parties, it is also represented by an increase in thecapital value of property. Other indirect economical advantages are linked with the non-marginaleffects on the financial statements of the local government agencies, caused by higher urbandevelopment, income and property value generation. Moreover, anticipating flood helps to avoid thatphase of disruption in the entity’s normal operational activity and of its financial statements, which maylast several years and have negative financial and administrative repercussions. Although the twoproposals offer almost similar safety conditions, the Alternative proposal might encounter, at least inthe initial stages, a slight opposition, due to the long “militancy” by many administrations in favour ofthe construction of the water retention basins as planned by the Abridged plan.If the basins envisaged by the Abridged plan are constructed, the administrations of theMunicipalities affected by the works to improve the flood capacity of the river will face burdensdue to the economical and environmental loss suffered by the territory. Whereas the financial damagesuffered by the entities may be viewed as being negligible, the deterioration of the environmental capitaland of the place attractiveness is much more significant and may entail repercussions on the futuredynamics of local development. These effects may also take place in the territories downstream of the 52 Even if the attention to the safeguarding of the soil commercial value and economical development aims to mitigate or radically change this engagement.

52

works due to the changed water downflow, thus turning the neighbouring municipalities intostakeholders. As a result, it is not surprising that local administrations of this area are opposed to a lossof opportunities, which is not matched by any positive return for their own territory.If the works envisaged by the alternative hypothesis were to be carried out, all the coastalMunicipalities to the south of the bridge of Casarsa della Delizia up to Latisana, would beaffected. These entities might incur charges similar to those indicated for the area situated furtherupstream, but of a lower amount as they would depend on the characteristics of the affected area andof the planned works. For the Municipalities of the more southern stretch, these costs may be morethan compensated by the interest in their own hydraulic safety: the same Administrations which ask forthe safeguard would have the works on the territory to guarantee that safety. The part located moreupstream would not gain significant hydraulic benefits, however, through a relatively inexpensivemodification, it would be possible to use one of the weirs as a bridge, thus offering indirectly quiteinteresting benefits.53

The Friuli Venezia Giulia Region is interested in the simultaneous achievement of the safety,environmental and economical objectives to guarantee a sustainable development and satisfy theadministrations and populations involved.The Entity participates directly also with regard to the financial aspect, as it is the main resourcesupporting the carrying out of the works and one of the most involved parties in protection and post-disaster management actions.The Veneto Region has similar concerns, but its interest in the issue is not as “high” because the areaand the population involved are much less than those of Friuli and also because its territory suffersfrom other important hydrogeological safety problems. The possibility that the Municipality of SanMichele al Tagliamento might pass to the Friuli Venezia Giulia Region may reduce the attention paid tothis basin.The European Union, through its regulations and the distribution of community resources, expressesa policy and, in this way it indirectly represents the interest of a much larger community for a specificsector or a local project. In this case, Directive 2000/60/EC is a clear reference point, whichimplementation laws may make less rigorous yet mandatory. Just as binding are the regulations,providing for the set-up of the European environmental network that, among other initiatives,introduces the protection of NATURA 2000 sites. An important role might be played by the StructuralFunds, which may express interest in the Tagliamento by providing financial support for part of theprojects (if these prove to be in compliance with Community policies). Finally, also Justice communityinstitutions might intervene, by representing private or prevailing interests, which may have beenprejudiced.The mission of the Water Authority is to guarantee hydraulic safety and cannot but be in favour ofactions, which reduce current risk levels.

53 The bridge would connect the village of Rosa with the ancient parish, which was abandoned on the opposite bank of the river to protect the village fromhydraulic risks.

53

SECTORS/INTEREST

GROUPS

INTEREST LOCATION TYPE OFASSOCIATED

VALUE

No-actionalternative

Abridgedplan

hypothesis

Alternativehypothesis

PRIORITY

1 ADMINISTRATIONS1.10 Local administrations1.11 Municipalities Less calamity risk, less prevention costs,

increased tax receiptsC DNE/IE/INE/D

E- + +/- 1

Preservation of environmental quality,increased tax receipts

A DNE/INE/IE + - + 2

Preservation of environmental quality,increased tax receipts

B DNE/INE/IE +/- +/- - 2

1.12 Provinces Increased safety of the territory and ofthe road infrastructure

T DNE/INE/IE - +/- +/- 3

1.20 RegionFriuli Venezia Giulia Increased safety, reduced land

management costs, environmentalquality preservation, increased taxreceipts

T DNE/IE/INE/DE

- +/- +/- 1

Veneto Increased safety of the territory,reduced land management costs

T DNE/IE/INE/DE

- +/- +/- 3

1.30 European Union Safeguarding environmental values(financial support provided for theregional development)

T INE (DE) - - + 3

1.40 Water Authority Hydraulic safety T DNE /IE - + +/- 1

Legend/key

Type of involvement Location Intensity of involvementDE direct economical-financial A Between Pinzano and

Spilimbergo1 primary involvement

IE indirect economical-financial B Between Codroipo and Varmo 2 deep involvementDNE direct non economical-financial C Between Varmo and the mouth 3 average involvementINE indirect non economical-financial T The entire area/cannot be

defined4 weak involvement

b) Private partiesPrivate parties, which are more concerned about the hydraulic safety of the Tagliamento, areproperty owners, entrepreneurs, residents, service providers and users.Property owners are directly interested in safeguarding their assets and in the possibility ofincreasing their value as well as the income produced. Landowners and owners of premiseslocated in flood-prone areas will be but in favour of actions aimed at minimizing the frequencyand intensity of the event, even if the feeble awareness of the risk weakens the strength throughwhich this interest is expressed.54 The parties with the highest values at stake are the owners ofassets situated in the P3 zone and those owning building areas, the use of which is conditional tothe possible urban choices under the different scenarios. As the probable loss in value offarmland is less important, this category of landowners is less sensitive to the problem andtherefore less easy to involve.The majority of the areas interested by the construction of the water retention basins is StateProperty. In this case, the capital interest is subordinate to the general public interest ofenvironmental and social nature. Based on information, which have not yet been verified, thereare privately owned surfaces in both sites. This situation would highlight a private propertyinterest that, in the absence of an adequate return, could not but oppose a worsening of existingconditions. A similar attitude might be taken up by those who own the interested surfaces duringthe costruction phase, but also by owners of the external ones, which although might not sufferdirect damages, could witness a loss in the market value of their assets.

54 According to a phone consultation with some estate agencies of the area, it came out that the sensitivity of the housing and the building lots market tothe hydraulic risk is attenuated in the months following the occurrence of the risk.

54

SECTORS/INTERESTED

GROUPS

INTEREST LOCALISATION ASSOCIATEDVALUE BY

TYPE


Abridgedplan

hypothesis


PRIORITY

2 PRIVATE PARTIES2.10 Real estate owners2.11 Farmland safeguarding real estate A DE/IE + - + 3

safeguarding real estate B DE/IE + + - 3safeguarding real estate C DE/IE - + + 3

2.12 Building area increase in real estate value C DE/IE - + + 22.13 Buildings increase in real estate value and land income C DE/IE - + + 2

2.20 Entrepreneurs2.21 Farmers reduction in the risk of crop losses, reduction

in the risk for structures and meansC DE/IE 2

reduction in the risk of crop losses A DE/IE/INE + - + 2reduction in the risk of crop losses B DE/IE/INE + + - 2

2.22 Inert extraction increase in extraction, reduction in the riskfor structures and means

A DE/IE/INE + - + 4

increase in extraction, reduction in the riskfor structures and means

B DE/IE/INE + + - 4

2.23 Constructions increase in revenues T DE/IE/INE - + +/- 3reduction in the risk for structures andmeans

C DE/IE/INE - + +/- 3

2.24 Craftsmen reduction in the risk for structures, means,products

C DE/IE/INE - + +/- 2

2.25 Manufacturers reduction in the risk for structures, means,products

C DE/IE/INE - + +/- 3

2.26 Trade and services reduction in the risk for structures, means,products

C DE/IE/INE - + +/- 2

2.27 Tertiary (other) reduction in the risk for structures andmeans

C DE/IE/INE - + +/- 2

2.28 Public service managers reduction in the risk for infrastructures andmeans

C DE/IE/INE - + +/- 3

2.30 Residents and operators2.31 Ground floor residents

with cellar/basementreduction in the risk of assets, reduction indisruptions

C DE/DNE/IE/INE

- + +/- 2

2.32 Residents other storeys reduction in disruption C IE/INE/DNE - + +/- 22.33 New residents increased opportunities C IE - + +/- 42.34 Operators reduction in disruption/loss of income C DE/IE/INE - + +/- 32.35 New operators increased opportunities C IE - + +/- 4

2.40 Service users2.41 Public transport reduction in disruption C DNE/IE/INE - + +/- 32.42 Private transport reduction in disruption C DNE/IE/INE - + +/- 3

improved connections B DNE/IE/INE - - + 32.43 School and health-care reduction in disruption C DNE/IE/INE - + +/- 32.44 Administrative reduction in disruption C DNE/IE/INE - + +/- 32.45 Private urban reduction in disruption C DNE/IE/INE - + +/- 32.46 Recreational and

culturalreduction in disruption C DNE/IE/INE - + +/- 3

2.47 Tourists reduction in disruption/territory enjoyment C IE/INE/ - + +/- 42.48 Potential users better access to services/increased services C IE/INE - + +/- 4

2.50 Other partiesAssociations of anglers,hunters or cultural ones

maintaining cultural and environmentalservices

A DNE/IE/INE + - + 2

maintaining cultural and environmentalservices

B DNE/IE/INE + + - 3

Technical-scientificcommunity

technical and scientific contribution,prevailing position, prestige, professionalappointment

T DNE/IE/INE/DE

- +/- +/- 2

Legend/key

Type of involvement Localisation Intensity of involvementDE direct economical-financial A Between Pinzano and


IE indirect economical-financial B Between Codroipo and Varmo 2 deep involvementDNE direct non economical-financial C Between Varmo and the mouth 3 average involvementINE indirect non economical-financial T The entire area/cannot be


55

In the area where the water retention basins and related works are planned to be carried out, theentrepreneurs seem to be more concerned than the real estate owners. In case of 100-year floods,entrepreneurs operating in these areas would suffer damages to structures, means and interruption ofactivities due to the inflow of water and its permanence for a number of days. If flood events weremore frequent, partial flooding of one or more basins with lower storage capacity (for water masses andpermanence) would significantly reduce the extent of damages suffered. Farmers are the entrepreneurs,which are mostly affected as they use a large share of the surfaces planned for the basins. They wouldbe influenced in the choice of crops on the basis of possible damages to both crop and equipment, butalso in the strategic decisions made taking into account the greater use limitation and increaseduncertainty. Farmers represent one of the strongest and organised categories opposing the carrying outof the works. Mining activities as well are affected by the modified hydraulic regime. In this case, inaddition to the temporary disruption in activities there is also the risk for plants and equipment and thecharges to restart productive activities. The parties carrying out mining activities are not a strongcategory among the interested parties as their activities are less widespread, they are used to the riverand its effects, and there is the possibility of safeguarding most of their investments. Otherentrepreurial parties located in the area surrounding the water retention basins (and with economicinterests of a different entity, depending on the type of activity and on how close they are to the works)may become important actors in the decision-making process, if they are able to organise themselves asa powerful pressure group. Although the individual damage is more contained and not easilyquantifiable, tourist operators, farmers, breeders, manufacturers belonging to sectors which aresensitive to the link with the territory may associate to ask for the present situation to remainunchanged, to prevent future modifications to their own operational context.The parties, which are strongly interested in the hydraulic safety of their own territory, are theentrepreneurs located in those areas, which are not sufficiently protected. In this case, the enterprises,which demand protection, are activities, which involve a high level of investment and/or added valueby surface unit. Craftsmen, traders, tertiary operators are the ones which are more likely to incursubstantial direct and indirect losses and also those of the group which more strongly support theovercoming of the current deadlock with regard to the construction of the works to increase the floodcapacity of the river. Other parties, even if less in number, such as industrialists and public serviceproviders may pay a lot of attention to the limitation of the risk which their assets and activities may beexposed to and decide to join forces with the previous groups with regard to the request for action.The building sector does not present particularly sensitive risks, however it may enjoy a remarkableboost as a result of both the carrying out of massive works, such as the proposed ones, and the need tocarry out restoration works after the flood.In case of a flood, the residents of the area at risk are the category, which would suffer the majorconsequences. For these parties, material losses may be considerable taking into account the familybudget and, as a whole, represent the main expense item. The residents of ground floors or houses withcellars, in particular in the P3 zones, are the parties which face the greatest risks, however all theinhabitants of the flood-prone area are affected as far as danger awareness is concerned, the restrictedopportunities as well as the disruptions and problems which a flood entails.These parties represent the largest powerful group, even though they are less organised than othereconomic categories, with the possibility of exerting pressure on the choices, both directly and throughthe assent of those political forces, which support their interest.Non-resident operators are less important actors as they simply suffer the risk of a temporary job lossand possible long-term repercussions in the occupational levels. Similarly, all potential new residentsand operators have interests at stake, in that they may miss opportunities due to the risky situation orbecause of flood events, but they are not given due consideration.Moreover, also service users are among the parties, which are scarcely represented. The risk ofdisruption in services provided, such as those provided by public transport, schools, healthcare system,local government agencies, recreational and cultural centres, affects urban settlements, but it involves afar greater number of people than just the residents and operators. This uncertainty may have

56

repercussions also on long term choices, hampering the development of new services and thestrengthening of existing ones, with limitations for current and potential users.All the categories of residents and users that pertain to the risk-prone area demand, though withdifferent degrees of intensity, actions to guarantee safety. In the case of economical operators, thehypothesis of carrying out the water retention basins at Pinzano may initially encounter a net preferencebecause it is already in the pipeline. In the first phase, the alternative hypothesis may reap a mixture ofhostitility and interest and only later be evaluated with regard to its technical content, and eventuallybecome the first option in case the present deadlock last longer than expected.The “voiceless” parties include the tourists who, although from an economical and cultural point ofview are becoming increasingly more important and concerned about the preservation of theenvironmental and historical-artistic quality of the sites, are not a recognised pressure group55.Other categories, though numerically less strong, may take up a significant role in the decision-makingprocess. Groups concerned with the naturalness of the Tagliamento, such as fishermen, huntersassociations and cultural clubs, may become very resolute groups in opposing the carrying out ofstructures in the riverbed and may be capable of involving other local parties and act as their point ofreference.Finally, there is an additional category of parties, which plays a significant role and has no direct bondswith the territory under examination. It is the category of the technical-scientific community, which hasdedicated a lot of attention to the hydraulic safety of the Tagliamento and continues to do so. In thisregard, opinions differ. Two lines of thought may be identified: the one supported by the Italian expertsof hydraulics, approving the works to increase the flood capacity of the river in the middle reaches ofthe river and the other one supported by European and Italian scholars of hydrology andenvironmental sciences who oppose the project. It is difficult to understand the effects of theintroduction of a new hypothesis before it is carried out, however, if it were possible this wouldundoubtedly have significant repercussions in the debate under way.

c) General publicSome interests involved in the decision regarding the construction of the works for theimprovement of the flood capacity of the river cannot be ascribed to a specific social category,but to the community as a whole, both locally and at large.The historical and environmental heritage is important, as it is a means of building a sense ofidentity but also an opportunity of enjoyment, and the local communities, along with thosebeyond the regional boundaries in proportion to the value attributed to such heritage, have itssafeguard at heart. Environmental associations and institutes for the conservation ofartistic works voice these collective needs and represent an important factor in the decision-making process. In the case of the Tagliamento, the most remarkable action is supported by theenvironmental organizations that, though with heterogeneous positions, oppose the constructionof the water retention basins in the middle reaches of the river.Among values of public interest, worth of notice is social cohesion, which is particularlyimportant at both local and regional community level. The little attention paid in this first phaseof the administrative procedure to the participation and negotiation between administrations andother social parties contributed to create a climate of sharp confrontation. A shared solutionappears rather difficult at present and the alternative hypothesis may be able to bring theconfrontation to a successful conclusion.The regional community plays decisively a very important role in terms of interests at stake.The regional and national subjects, as taxpayers, take up the burden of the construction works, aswell as that of the partial restoration of the damages. The general interest, therefore, hopes forthe most appropriate allocation of resources in terms of obtainable benefits versus costs to besustained. In this light, the priority assigned to the retention basins should result from thecomparison with other projects under examination (concerning hydraulic safety, but also healthand welfare sectors).

55 Their requests are partly supported by the economic sectors linked with tourism and organizations for the protection of the common good.

57

Last but not least, there are the political parties that, despite representing directly only part of thepopulation, are capable of encouraging and guiding public consent on specific collective choices. Untiltoday, their role has not been significant, as the position was dominated by the geographical positionrather than by the political belonging: representatives of the same political forces presented themselvesto the electorate with contrasting positions with regard to the construction of the basins, depending onthe catchment area. This situation is going to last for quite some time, unless the debate on theTagliamento does not become a fighting ground at regional level or wider mediation processes areinitiated.

In addition to the actors directly involved in the decision regarding the detention basins, other partiesmay be interested in considering also the other possible measures set out in the first chapter (ReferenceContext). In this case, the stakeholders would be the farmers of the upper catchment area and of thoseriparian areas which over the years have operated as natural detention basins, the dwellers and the realestate owners of these areas, the Reclamation consortia, the managers of infrastructures, educationalcommunities, non-profit organizations and, in many cases, among the actors playing an important rolewith regard to planning and carrying out the actions.

SECTORS/INTEREST

GROUPS

INTEREST LOCATION TYPE OFASSOCIATED

VALUE


Abridgedplan

hypothesis


PRIORITY

3 GENERAL PUBLIC3.10 Collective parties3.11 Historical heritage heritage protection and possibility of

enjoymentC DNE/INE - +/- +/- 4

3.12 Environmentalheritage

heritage protection and possibility ofenjoyment

A DNE/INE + - + 2


B DNE/INE + + - 2


C INE - + + 4

3.13 Social cohesion stronger sense of identity andparticipation

A DNE/INE + - + 2

stronger sense of identity andparticipation

B DNE/INE + + - 2

stronger sense of identity andparticipation

C DNE/INE - + + 3

3.14 Economicdevelopment

increased product added-value T IE - + + 3

3.15 Future generations value conservation and use opportunity T IE/INE - -/+ + 4

3.20 Regionalcommunity

improved regional system, reducedpublic spending

T IE/INE - +/- + 3

3.30 Political parties collective problems solved, agreement T DNE/INE - +/- +/- 2

(*) The breakdown indicated is by type of interest. The stakeholders should be identified in the local community and in different parties (local,national and international associations)

Legend/key

Type of involvement Location Intensity of involvementDE direct economical-financial A Between Pinzano and


IE Indirect economical-financial B Between Codroipo and Varmo 2 deep involvementDNE direct non economical-financial C Between Varmo and the mouth 3 average involvementINE Indirect non economical-financial T The entire area/cannot be


SUMMARY EVALUATION

a) Verification of the economical-financial feasibility of the actions.

The financial analysis was performed using the net present value criterion (NPV) and the Cost-Benefitratio. The benefit of the actions was calculated as being equal to the net present value of the uncertain

58

damages caused by the 100-year event. The above value was increased by the benefit resulting from thedamage reduction due to less frequent events56. The discount rate used was 2%.On the basis of prudent estimates, under the scenario defined by the “Sarno” zoning, the constructionof defence works generates a financial benefit ranging between approximately 53.15 and 73.58 millioneuros for the Abridged plan and the Alternative hypothesis respectively. Both NPVs are positive,however, the hypothesis of increasing the flood capacity of the river further downstream ispreferable compared to that of the Abridged plan.The difference is greater if the cost-benefit ratio (C/B) amounting to 1.55 for the Abridged plan iscompared with 2.17 for the Alternative hypothesis.

No-action

alternative

Abridged

Plan

Alternative

hypothesis

construction of detention basins 77.47 50.39

maintenance (net present value of yearly costs) 19.37 12.60

Total works 96.84 62.99

damages due to 100-year event (Sarno scenario) 218.16

benefits (net present value of damages) 149.99 136.57

NPV 53.15 73.58

C/B 1.55 2,17

Thus, by comparing the hypotheses which have been put forward, the alternative proposal appearsto be more economically viable due to the higher net present value generated, but also due tothe lower capital layout required by the works.For a more objective evaluation of the social benefit of the investment, due to cutbacks in publicspending, this information should be compared with that relating to other actions (also in the field ofhydraulic safety programmes)57.

b) Community Impact Analysis

At present, the confrontation between the various subjects, communities and administrations is radicaland hinders a smooth decision-making process. With a certain degree of approximation one might saythat the main coalition force, which considers the hydraulic safety as a top priority and is in favour ofconstructing water retention basins in the middle reaches of the Tagliamento, includes theadministrations, political forces and the majority of civil society living in areas which are not sufficientlyprotected, sided by a large group of people from the academic and the technical world. The abovecoalition is opposed by the administrations, political parties, cultural and trade associations of themunicipalities of the middle course of the Tagliamento, which are supported by internationallyrenowned scientists and by all the main environmental organisations.The situation has been in a stalemate for a long time. The community impact analysis may offer acontribution to overcome the status quo, starting from the recognition of the fact that there are manyinterests at stake and just as many stakeholders. The value of the losses and gains for each category ofsubjects is not uniform and it is difficult to calculate, however, each interest represents a significantelement for the respective stakeholder.By recognising these interests it may be possible to overcome frontal confrontation and start acoalition process with regard to elements upon which there is wide agreement, which arenumerous even though not explicit, but also a confrontation process with regard to the concurrentobjectives in order to identify solutions which everyone considers fair and not penalising.

56 This damage was estimated by calculating the NPV of an amount equal to 75% and 50% of the 100-year event damage for the hypothesis of theAbridged Plan and the alternative one based on a 200-year event, respectively. The different contribution amounts depend on the assumption that thegreater storage capacity of the water retention basins envisaged by the Abridged Plan could generate, in case of greater tha 100-year events, higher benefitsthan the alternative hypothesis, assuming that the greater efficiency of the basins of the latter would not compensate for lower storage capacity.57 In addition, it is should be recalled that the basic hypotheses (accounting for basin costs only, lack of non structural and other measures) may be a topicof discussion and “negotiation” with regard to the overall strategic planning for the basin.

59

In this regard, the introduction of a third option lying between the Abridged plan and the no-actionalternative which envisages leaving things as they stand, could be decisive to hesitate no longer andopen up the possibility of negotiations. Such an opportunity must not be missed and should beexploited to strengthen participation and initiate a strong negotiating action, to allow theparties pursuing different objectives to confront each other and converge towards solutionswhich are of a clearly high collective interest and which attempt to meet the various types ofneeds.

CONCLUSIONS OF THE ECONOMICAL AND COMMUNITY IMPACT ANALYSIS

The cost-benefit and community impact analysis lead us to believe that there are convenience reasonsand large convergence spaces for actions whose objective is to guarantee the safety of the populationsof the lower course of the Tagliamento and the preservation of the environmental heritage representedby the river ecosystem.

To attain these objectives, it is necessary to overcome the current phase, characterised by contrastsbetween local communities and social sectors as regards the hypothesis to carry out water retentionbasins downstream of Pinzano, a situation which is slowing down other possible actions, even ordinaryones. This can take place only through a process, which envisages the following:a) focusing on objectives and planning a coherent system of actions;b) developing new project hypotheses for the mitigation of the flood wave paying attention to

hydraulic efficiency, but also taking into account the set of objectives and interests of the variousactors;

c) implementing new forms of participation and negotiation.

a) Focusing on objectives and planning a coherent system of actions

“Defusing” the controversy over the water retention basins is of fundamental importance. It meansshifting the attention of the debate on actual objectives to be pursued: the safety of the community andthe preservation of the fluvial ecosystem. There is large convergence over these two objectives andfrom that common ground it is possible to restart and overcome the confrontation generated byfocusing the reasoning on a simple project.Safety of the community means safeguarding all those values, which are non-negotiable (human life,above all) and reducing the social damage to a minimum (losses of economic nature, of environmentalvalues, possibilities of use, disruptions). International experience indicates that in case of floodsthe safeguarding of human lives depends on the population awareness of the risk and on theactions to be carried out, as well as the arrangement of adequate emergency measures. Ifavoiding the loss of human lives is part of the safeguard objective, in this respect there is wideagreement on the possibility to act immediately.The reduction of economic losses represents in order of importance the second element of safety, andone, which at present is likely to prevail. If the values at stake are of economic and financial nature, theabove is a significant judgement scale to establish whether action is worthwhile or not. This criterionexcludes expensive actions, which restrict damages due to events with an extremely low probability ofoccurrence.With the economic rationality as our starting point and with the awareness that no thaumaturgic actionexists, it is possible to agree upon a wide range of actions aiming at minimising damages and disruption.In this respect, the various possible actions should be analysed on the basis of their effectiveness(contribution to reduce the extent of damage), efficiency (having a high cost-benefit ratio), but also theability to guarantee the other objective at stake: the preservation of the fluvial ecosystem.The actions, which need to be implemented to reduce the economic damage, should also take intoaccount urban policies, structural actions and financial measures.

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In conclusion, in the light of the renewed relationship between the river and its territory which is aconcept that is beginning to establish itself in Europe, it is worthwhile underscoring the need to plan aseries of actions distributed throughout the territory, in order to increase the naturalwidespread flood capacity of the river and avoid any hasty and isolated actions, which areinevitably the harbingers of environmental impact and possible enormous risks for theincorrect operation of the works.In this regard, it is important to consider all those actions that may reduce the probability of a floodoccurring, “govern” the overflow to contain the potential damages and protect the most valuableassets, such as:- actions on the catchment area, specifically aimed at increasing the widespread flood capacity;- legal, technical, protection or other measures, aimed at monitoring the territory of risk-prone areas;- ad hoc embankments to protect single valuable assets or areas exposed to a greater flood risk;- contained flooding (both in terms of water depth and duration) of areas with a lower concentration

of high-value assets;

For this reason, it would be important to know and evaluate the possibility of using the agrarian andreclamation network and quantify the volumes of water, which may be retained to mitigate floodsthrough the possible controlled and widespread distribution over part of the farmland. The mainproblem is to define the entity of the contribution of these events (in terms of reduction of the levelsand bankfull discharges of the flood) and the ensuing alternative or complementary role to the majorhydraulic works.

b) developing new project hypotheses for the mitigation of the flood wave paying attention tohydraulic efficiency, but also taking into account the set of objectives and interests of the variousactors;

As regards actions aimed at mitigating the flood peak, the proposal to increase the flood capacity of thelower and middle reaches of the Tagliamento has the first and foremost merit as it highlighted theexistence of actual alternatives to the actions proposed by the Abridged plan in this field.Even if the information base required to finalise the project proposal is still incomplete and needs to befurther integrated, as indicated in the conclusions of the study conducted by the team of Prof. Todini,the proposal to carry out the detention basins closer to Latisana is more advantageous from aneconomical, social and environmental point of view, compared to the proposal which envisagesthe basins at Pinzano. The result, emerging from this analysis and the one performed by the“environmental” workgroup, shows that the hypothesis of the Abridged plan, developed as a prioritysolution to the hydraulic safety problem of the Tagliamento, has, in fact, become the main obstacle toachieve this objective.In this regard, the formulation of new action hypotheses for the mitigation of the flood peak and thedecision to opt for one or another will be carried out with clearer objectives in mind, up-to-dateinformation and appropriate evaluation methods, re-assigning to the Water Authority the role andresponsibility to elaborate new technical proposals.

c) Implementing new forms of participation and negotiation.

The hydraulic safety and the safeguard of the Tagliamento are absorbing issues, which should be solvedby all the communities and administrations present on the territory crossed by the river. In this regard,participation and negotiations take up a central role. These functions should not be considered asinstrumental to obtain agreement upon the construction of works, which is in itself a considerable fact,as it is revealed by the much disputed procedure of the Abridged plan, but they should be targeted toobtain the best possible results and enhance the value of contributions as well as of the opportunitiesexisting in the operational context. For this reason, alongside a clear allocation of responsibilities andthe strengthening of coordinating structures, it will be necessary to establish ways of including all the

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parties and communities which are directly affected and to promote active participation to solvingshared problems. In this area, some progress was made, especially with regard to the institutions, butfurther steps are still outstanding and should be made as soon as possible. A boost in this directioncomes from the extension of subsidies both vertically and horizontally, from Community rules in thisparticular sector, but especially from the development of a culture as well as of the achievement offorms of active democracy and evaluation of public actions.

These conclusions may represent the basis for operational planning, which might encompass thefollowing actions, analysed by objective groups:

a) Knowledge area (preliminary actions)actions aimed at improving the effectiveness of actions within all the fields described hereafter:- updating and refining risk and territorial value maps;- further development of the flood forecasting system.

b) Population safety policiesThese are actions aimed at safeguarding people’s lives and to reduce damages and disruptions incase of flood:- sharing of the civil protection plan and action coordination;- updating of all civil protection structures and infrastructures;- circulation of the civil protection plan and developing individual action plans.

c) Prevention and damage reduction policiesInstruments aimed at reducing potential damages through an active policy of protecting allexisting values. It includes measures to improve the spatial distribution of new settlements, worksto protect assets and activities (valuable or representing a risk) and to reduce the number ofvaluable assets at risk. These actions fall mainly within:- territorial planning- agricultural and forest policies.

d) River management policiesThese policies include actions to preserve the quality of the environment and improve hydraulicsafety. The guidance role played by the Water Authority and by the Regions might be to ensure:- the strategic planning for the Tagliamento,- coordination and participation by local administrations and communities,- the carrying out of infrastructural works in accordance with pre-established priorities.To support this action policy, it would be extremely useful to:- establish a Tagliamento Community in order to increase fields of joint action in the policies

concerning the two banks of the Tagliamento and avoid conflicts;- participate to networks with other European entities to exchange experiences and launch

experimentations, also taking advantage of the resources that the European Union providesfor these purposes.

e) Guarantee policiesThese are instruments aimed at promoting recovery when natural calamities occur. In this case, aspublic funds available are limited, supporting a pilot project which promotes private insurancepolicies against flood damages (informative material, promotional activities, incentives) ispreferred to the setting up of a specific regional fund.

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TOWARDS AN INTEGRATED MANAGEMENT PLANOF THE TAGLIAMENTO BASIN

The European experience shows that both the selection and integration of the various possiblemeasures need to be evaluated on the basis of the specific characteristics of the watercourse and theterritory under examination. Different mixes of various measures characterise the action depending onthe frequency and magnitude of the event, on whether the event occurs in a mountainous or flatground area and on whether there is a high or low concentration of settlements and valuable assets.If it is true that, especially with regard to the Tagliamento, there are actions, which may contribute(jointly and/or as an alternative) to achieve the safety and the fluvial ecosystem preservation objectives,international experience demonstrates that it is no longer possible to disregard a deep knowledge of thehydrological, geo-morphological and ecological features of the entire watershed58. In order to achievethis, it is necessary, urgent and essential to acquire complex knowledge deriving from themultidisciplinarity of skills and from the participation of those who live and carry out theiractivities along the river by involving actually and actively the basin communities.

This study, in fact, highlights the serious lack of data, hence of knowledge, regarding manyfeatures of the Tagliamento watershed, on which the safety of the riverine people and thefuture of an important part of the Friulian territory heavily depend.

This lack of culture must and may be compensated by a multidisciplinary team of specialists which,in cooperation with the Water Authority, would work not only to carry out timely and isolatedactions along the river corridor, but would plan for an integrated management of the basinaimed at guaranteeing the hydrological and ecological functionality of the river. This would beachieved by envisaging the safeguard and value enhancement of natural areas which are stillpresent and taking into account all the problems which affect the fluvial corridor59, byidentifying appropriate action measures which are in line with the principles established byDirective 2000/60 EC.

Today the Friuli Venezia Giulia Region has the opportunity to play a leading role in aninnovative process within a European context, in which great are the expectations for themanagement decisions affecting the Tagliamento basin which, besides being a reference ecosystem forthe Alps and an internationally important ecosystemic model, might also become an importantintegrated and river management model at European level.

The hypothesis, which attempts to turn the river corridor into an area of international interest,is in fact absolutely realistic and would generate definite and long-term advantages with regardto both socio-economic and environmental aspects. Technically the conditions exist; what isneeded now is the political willingness to pursue the path whereby hydraulic safety isguaranteed by promoting the restoration of the hydrogeological and environmentalequilibrium also through the preservation of ecological processes and the definition of ascenario, which allows the identification of actually sustainable management choices.

58 The construction of detention basins to increase the flood capacity of the river is certainly an effective way to safeguard urban centres in heavilyanthropized territories. However, although these basins must comply with strict hydraulic engineering techniques, a wider approach should be adopted bytaking into account both the geo-morphological and ecological aspects of the river.59 Pollution due to the Burgo paper mill, lack of water due to withdrawals for hydroelectric and irrigation purposes, eutrophication due to intensiveagricultural practices, excavations and removal of inert material, etc.

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ANNEX 1

COMPARISON OF THE TWO HYDRAULIC PROPOSALS

Abridged plan Alternative

No. of concerned municipalities 560 961

Site of Community Importance (SCI) YES NO

Height of dikes 6.20 – 8.60 m 1.5 - 5 m

Retention basin volume (in millions m³) 30 21

Retention basin area (in millions m²) 9 11

Apron YES NO

Impact on water table YES NO

River continuum interrupted uninterrupted

Costs/Benefits 1.55 2.17

NPV 53.15 73.58

60 Dignano, Pinzano al Taglaimento, Ragogna, San Daniele del Friuli, Spilimbergo61 Camino al Tagliamento, Codroipo, Latisana, Morsano, Ronchis, S. Martino al Tagliamento, San Vito al Tagliamento, Varmo and Valvasone

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ANNEX 2

TOWARDS AN ACTION PLAN FOR THE TAGLIAMENTO RIVER

This section wishes to provide an extensive though incomplete framework of the possible actions(many involving a combination of actions, others just a simple alternative) on the Tagliamento River,which may contribute to the safety and preservation objectives of the riparian ecosystem.

1. Recovery of the soil retention capacity and reduction of the meteoric water inflow in theriverbed

a) Protection of the soils and of the minor hydrographical network. To ensure that current averageudometric coefficients are preserved and improved and hydraulic functionality increased, thisaction should affect the entire basin. This would entail checking the present status, theidentification of the best soil management practices (to integrate currently used planninginstruments) and of the actions aimed at “reducing” the water outflow through works whichcould at the same time improve the local environmental equilibrium. Extensive control requiresthe co-operation of the population and of the institutions in charge of the whole basin as well asactions concerning the management of agriculture, forest conservation, minor tributaries and lastbut not least currently or originally humid areas. Unlike the past, today this type of actions ismuch more feasible thanks to the reduced anthropic pressure on mountainous areas, adequateagricultural policy measures, a greater interest in the bio-diversity preservation as well as to thereconditioning of sites intended for tourist and recreational purposes to their natural status. Allthe above actions can rely on European Union funds.

b) Co-ordination of the management of water bypass, retention and discharge systems of the entirerivercourse and its tributaries. Recent flood events highlighted that the numerous by-pass andretention system works affecting the river-courses were inefficiently managed. In case of adverseweather forecast, on the days and hours prior to the expected flood, the structures designed tomitigate the river discharge must operate in concert in order to reduce any possible risk.

c) Land maintenanceMaintenance carried out to the Tagliamento basin with the aim of preserving the environmentalequilibrium or maintaining it stable must guarantee the functionality of the ecosystem throughregular and widespread actions to manage:• any renaturalisation process (recovery of outflow and humid areas);• environmental recovery;• environmental impact reduction (reinforcing through naturalistic engineering techniques); and• any naturalistic management (woodland conservation and management, weed monitoring,

land environmental improvement, repopulation of autochthon species).In particular, land maintenance must guarantee the functionality of the ecosystem, the safeguardof the ecological continuity, the protection and stability of the autochthon biocoenosis. Landmaintenance can be carried out by different bodies (i.e. Park authorities, Consortia ofmunicipalities in mountain areas, Land reclamation consortia), co-ordinated by the WaterAuthority, which establishes the action plans and the joint action criteria.

d) Restoration actions and actions to ensure viable conditions for stable phytocoenosis inabandoned no-maintenance mountainous areasIt is imperative to identify those abandoned mountainous areas (but also other types of land)where activities were once carried out as well as those where it is either difficult to resumeprevious activities or guarantee adequate land use monitoring. In fact, the effects of the changeswhich have occurred in the use of the mountainous area of the Tagliamento basin do not appearto have been quantified as yet. These areas require specific land planning aimed at promoting therecovery of native vegetation, which would guarantee maximum ecological functionality (i.e.adequate water retention capacity) and no need for maintenance.

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2. Discharge increased at critical points (urban areas or areas where public utility structuresare located)

a) Raising of the embankments. This is one of the most traditional and widespread defence actionsagainst the hydraulic risk and it is linked to the increase in the average discharge of thewatercourse. Embankments are commonly used along flood-prone stretches and along stretcheswhere damages are expected to affect people or significant structures and environments(historical, cultural, social, environmental sites). Obviously, embankments cannot exceed certainlength and height limits due to technical reasons (even in the event of severe floods) but alsobecause of the effects on the surrounding environment. It is crucial that the embankments beproperly and regularly maintained so as to preserve their hydraulic functions and ensure, in caseof flood, that the river behaves according to its expected dynamics.

b) Elimination or reduction of physical impediments in the most critical river stretches. Increasingthe water discharge is a strategy that should be applied only to those stretches of the river, whichcross towns and are not sufficiently wide. In this case, the presence of obstacles, such as inertmaterials and riparian vegetation, can reduce the width of the river section, increase theroughness coefficient and, consequently, diminish discharge capacity. Regular maintenance to themost critical areas of the river carried out to ensure the effectiveness of the potential discharge aswell as the maintenance of the dike construction works are two crucial requirements. In certaincases, other elements such as the beams or the arcades of a bridge could represent an obstacleand possibly cause downstream overflowing and/or damage to construction works. The problemcan only be solved through infrastructure adjustments or the identification of additional outflowcorridors. However, it is necessary to verify the possibility of enlarging the hydraulic section ofthe river also within towns in order to promote the stability of riparian vegetation and improvethe scenic landscape of the town without affecting the hydraulic capacity and efficiency of theriverbed.

3. Abatement of the flood peaka) Actions on the main river course and its tributaries: reservoirs, lateral artificial schemes, in-line

detention basins62, as well as embankments, are the traditional solution commonly put forward byhydraulic engineers against any flood risk. The aim of the construction of the basins is to containa water volume sufficient to reduce the flood peak and therefore allow the river discharge withinthe riverbed. The safety level required is the one, which guarantees defence against a 100-yearflood event.It is however necessary to draft a plan allowing for the real-time co-ordination of all reservoirs,regulation areas and water by-passes in order to guarantee a joint management regime based oncommon and shared objectives, especially under water crisis situations (exceptionally high andlow river discharge). This co-ordination is also strictly related to point 5, which follows.

b) Regulation of the discharge through dikes or drainage channels. When the discharge exceeds theoutflow capacity within the embankments, the water outflow can be controlled and siphoned offto channels or areas designated to receive the water mass. Drainage channels may be viewed bothas a main device to control discharges and as a “safety valve”, after all other construction workshave gone into operation, in order to protect top priority areas from flood effects and direct areduced overtopping towards a territory where the economic, social and environmental impactwould be far milder. The possibility of using drainage channels with guided outflow areas ordischarge corridors has certainly been one of the least studied solutions. There is undoubtedly anumber of objective execution problems due to the characteristics of the flood wave and thewidespread land urbanisation, but this hypothesis is to be considered both as a direct device forthe abatement of the flood flow and as a management policy of extreme events which are greaterthan the reference events taken into account in other flood abatement projects.

62 The possibility of erecting a weir in Pinzano (already excluded by the abridged Plan) has been discarded since it is certainly considered lessadvantageous than the other two hypotheses, based on social and environmental criteria.

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c) Recovery of outflow areas and renaturalisation actions. With regard to the restoration of theecological functionality, areas for the recovery of the flood capacity of the river as well as areasfor its preservation and renaturalisation can be identified and delimited. Hence, the types ofactions to be carried out need to be identified.

4. Limitation of the potential damagea) Correct spatial planning and identification of town planning criteria leading to the reduction of

the potential consequences of the damage to people and structures, both public and private,(zoning, construction criteria for public infrastructures and service centres) should be carried out.A correct town planning has the aim of stopping the traditional practice of concentrating valuesin vulnerable areas, which eventually gives rise to a spiralling level of defence actions. Planningthe development of new settlements in lower-risk areas, updating networked services, the raisingof priority infrastructures along with appropriate construction criteria can prevent the currentsituation from worsening.The recently proposed Piano Territoriale Regionale Strategico – PTRS (Strategic RegionalTerritorial Plan) identifies the Tagliamento River as a fundamental element of the environmentalsystem of the Friuli Venezia Giulia region as well as of the Pan-European Ecological network,which guarantees the preservation of biodiversity. If the approach of the Piano TerritorialeRegionale Strategico – PTRS (Strategic Regional Territorial Plan) is confirmed, the ecologicalimportance of this area should be recognized by an Integrated Territorial Plan, which would bedefined and managed by all concerned municipalities.At present a lot can be done, at a municipality level, through the planning instruments currentlyin use while waiting for the implementation of new procedures, by adopting Law No. 267 of1998 (the so-called Sarno Law) and by paying more attention to the mitigation of present risksand by trying to ensure that their level does not increase in the future.Some policies relating to specific sectors, in particular the agricultural one, can contribute tostrengthen these territorial choices, by fostering land uses and technologies, which are compatiblewith damage reduction strategies.

b) Construction criteria suitable to reduce flood damages. The flooding of buildings happens mainlythrough openings in basements, doors and any other part connected to the external perimeter.The vulnerability of buildings depends on whether these elements are present, located aboveflood depth as well as on the implementation of appropriate defence measures. This applies tohouses, but also to production facilities, which should adopt adequate construction techniques(absence of cellars and basements, construction level, types of window and door frames) for thevarious levels of risk.Innovative and adequate construction techniques should be identified and their use mademandatory for all new settlement areas. This hypothesis, which private citizens may findpenalising and hard to accept, can be integrated and mitigated by specific urban or tax reliefs.

c) Different protection levels depending on the values to be safeguarded. If preventive measures canbe adopted for all new construction works, ad hoc protection countermeasures should be appliedto all existing ones. Normally, most of the damage is suffered by small urban areas (old towncentres, shopping and industrial areas) or single facilities (hospitals or delicate infrastructures), therest of the territory (cultivated areas, scattered houses) being only partly affected by it. Theeconomic and social damages, but also any environmental and cultural ones, can be significantlyreduced, if works for the safeguard of limited areas of the territory are carried out. Historicaltown centres and places with a high cultural value, structures offering essential services as well assites which may cause severe pollution accidents are the first on the list when it comes toprotection since their cost/benefit ratio is undoubtedly favourable even in case of low-frequencyevents. Depending on each case, protection can be permanent (embankments, dikes, raisedaccesses, safety valves) or temporary (sheet piles for mobile dikes).

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Flood risk mapping can help identify all those land elements, which should be specificallysafeguarded. With regard to the lower course of the Tagliamento River, protecting only fewstructures could reduce the risk of serious environmental pollutions to a minimum and, thesafeguarding of some production sites could significantly reduce the extent of the economicdamage.

5. Defence from the exceptional flood eventa) Carrying out of protection works and providing monitoring tools and emergency means

Investment in civil protection resources generates the highest cost/benefit ratio, since importantsocial and economical welfare results can be achieved with low resource requirements. Aneffective action requires an appropriate forecasting and warning system for the population andthe arrangement of action plans. Effective warning means having a couple of hours to act safelyand this can mean the safeguarding of lives and a significant reduction of the damage. It isparticularly important to develop a plan, which takes into account all actions to be carried out tosafeguard the community and also responsibilities at all levels. Actions must be able to rely onequipped areas located in safe places as well as suitable means and qualified personnel.

b) Defence training of all population and shared planning of civil protection actionsBeing informed is the best weapon to safeguard people and reduce damage to goods andproperty. International experience shows that, in case of a flood event, the saving of human livesis possible only if the population is “fully aware and knows” the potential hazard and adoptsappropriate behaviour in emergency situations. Thus, the existence of a civil protection plan isnot enough as this should be spread or, even better, shared with the population. This actionshould lead each inhabitant of the risk-prone area to keep an “action plan” to be put into effectin case of need. The civil protection and, in particular, the forecasting service must enable peopleto carry out the plan in complete safety. A website where all information about the catchmentbasin and any related risk maps can be retrieved should be developed just as it happens in otherEuropean Union countries.In fact, despite the Civil protection is highly efficient, unfortunately, environmental calamities stillcause victims, suffice it to mention the recent flood events of the Canal del Ferro and Valcanale.The majority of these calamities could be avoided, if all the population had a “mental map” ofthe risks and also clear ideas on the actions to be carried out in case of emergency. This riskculture can be developed in a short period of time through targeted actions aimed at specificcommunities, public events, informative materials and other tools, which would help people toacquire specific behaviour to be adopted in case of floods.

6. Guarantee of restorationa) Guarantee funds constitute a traditional measure, which guarantees, without affecting public

financial planning, adequate support to those communities and single individuals affected bynatural calamities. Originally this instrument was highly reliable and generally covered the damage,however due to recent policy changes concerning cuts in public expenditure and in the number ofactions, it gradually lost its features. At present, state and regional guarantee funds represent onlya limited source of funds, whilst other financial instruments, promoted and participated by publicbodies, could be granted locally.In addition to all existing instruments, a specific regional guarantee fund may be set up. Theresources for this regional solidarity action could be obtained through a specific regional taxlevied on friendly-priced fuel.

b) Collective, individual or private insurance schemesInsurance schemes are becoming increasingly used as a means to recover damages caused bynatural calamities. Since total active defence from the event cannot be guaranteed, insurancecompanies offer the possibility of claiming damages to restore goods or property to their originalstate.

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Insurance policies are a “market instrument” however, they can be influenced by the public bodywhich could decide to make it compulsory (currently under examination by the EuropeanCommission, and included in the draft Financial Act 2004) or more easily promote a collectiveapproach and/or envisage a contribution towards the cost of the insurance premium.Even if this instrument does not reduce damage directly, it has undoubtedly a number of directand indirect advantages. In fact, to an increase in the demand for insurance policies wouldcorrespond a deeper knowledge of the risk-prone areas, which would lead to the drafting of moreaccurate risk maps. This knowledge and the resulting differentiation of insurance premiums mayfoster the culture of prevention with regard to the town planning and building sectors. Therelationship between annual insurance premiums, hazardousness and insured values may lead tomore attention being paid to the effects of floods when designing policies dealing with theallocation of areas to settlements and activities, as well as to promote the introduction oftechnical solutions of active protection.The existence of a wide-ranging insurance coverage on the territory may cause changes in thestrategy of the public body: the competition for resources between preventive measures andrecovery reduces and, in the light of the new framework of guarantees, protection objectives maychange.While waiting for regulations and the insurance market, both at national and European level, todevelop adequate instruments to reduce the negative financial effects consequent to floods,Regional authorities might promote feasibility studies and, eventually, support theexperimentation and implementation of insurance schemes for the communities and/or risk-prone categories.

In a logical ranking of priorities, countermeasures, which attempt to maintain the natural equilibrium ofthe river, would be preferred:- Soil management of the whole basin and maintenance of tributaries;- Maintenance of the natural flood capacity of the river;- Land planning to reduce the potential damage;- Community awareness and preparedness with regard to flood hazards.Where it is believed that the abovementioned actions could not guarantee a satisfactory level of safety,and only in that case, should actions aimed at modifying the fluvial dynamic be considered. At any rate,these actions should not substitute those aimed at preserving the natural equilibrium of the river andtheir financial and environmental impact must be proportioned to the expected social and economicdamage.

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ANNEX 3

RENATURALISATION

Renaturalisation is a combination of actions aimed at restoring the environmental characteristics andthe ecological functionality of an ecosystem according to its potential conditions, determined by itsgeographical location, its climate, the geomorphologic and geological features of the site and by its pastnatural history. Promoting renaturalisation on a large scale would be feasible only with a view tosustainable development, where the ecosystems forming the bedrock of human activities would regaintheir equilibrium through the reduction and control of the flows of pollutants produced as well as bytaking into account the hydro-geomorphologic, vegetational, faunal and micro-biological structure ofthe environmental mosaics. The new equilibrium attained with regard to any physical and biodiversityfeatures requires the restoration of new units which would naturally develop, according to precise,structural and functional rules, along with the existing artificial eco-mosaic units, i.e. renaturalisationactions. When these restoration perspectives are included in coherent frameworks of spatialrelationships, they become real multipurpose ecological networks, where nature perfectly coexists withenvironmentally friendly human activities. Renaturalisation can also be used to restore the pre-existingnatural conditions of an area and to achieve specific or intermediate objectives (i.e. recovery of theflood capacity of the river, reduction of flood speed; recovery of the river self-purifying capacity;preservation of precious species….).Renaturalisation should not be confused with techniques of environmental mitigation or landscapeinsertion, since their main objectives differ substantially. In fact, whereas the objective ofrenaturalisation is the restoration of environmental features (the reconditioning of a wood or a humidarea, the reintroduction of species, actions on the habitat or rare species, actions to contain infestingallochthonous species…) or of the ecological functionality (recovery of the outflow capacity, of theecological continuity and of the self-purifying capacity of a watercourse…), the main aim ofenvironmental mitigation techniques (through naturalistic engineering or different solutions oflandscape insertion) is to minimize any environmental impact or improve the landscape by carefullyplanning the location of any works or actions (for example, the consolidation of an escarpment throughnaturalistic engineering techniques is not a renaturalisation objective, rather an engineering one, i.e. theconsolidation of an escarpment). However, it is clearly advantageous to resort to techniques, whichallow appropriate environmental insertions and the exploitation of the biological features of any livingmaterials used, rather than rely on techniques or materials with high environmental impact. If properlyplanned and coherent with surrounding natural units, multipurpose mitigation actions (where projectworks are environmentally compatible) might be carried out along with specialised renaturalisationactions with the aim of restoring wide-ranging multipurpose ecological networks.As regards the Tagliamento River, actions having renaturalisation as a primary objective should be themain axis for the recovery of the hydro-geological and environmental equilibrium, of the river areas andthe water system. Restoring of the “flood pulsing” 2 of the fluvial ecosystem can be considered therenaturalisation objective of the Tagliamento River.

2 “Flood pulsing” is the idea that the physical and biotic functions of the fluvial ecosystem (represented by the riverbed and by the entire outflow river area) depend on thedynamic variations of the water discharge of the river itself” ( Middleton B., 1999 - Wetland restoration Wiley

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Summary table that shows possible renaturalisation actions identified (Extract from: WWF, Giovani Imprenditori di Confindustria, Coldiretti,2002. PATTO PER I FIUMI. La rinaturazione del fiume Po - Proposte per il bacino del Po. 2001 – 2002) (WWF, Young Entrepreneurs of theConfederation of Italian Industry, National Farmers Confederation, 2002. RIVER PACT. The re-naturalisation of the Po river - Proposals forthe Po basin 2001 - 2002)

Strategic objective taken from PAI Specific objectives Action typesTo guarantee a suitable safety level to the territoryof the Po river basin with regard to any hydraulic

Recovery of the hydro-geological equilibrium –Recovery of the flood capacity of the river

Restoration of oxbows and abandoned reaches (sector A)

and hydro-geological upheavals, through the Reducing the artificiality of the river banksrestoration of the hydro-geological andenvironmental equilibrium, the recovery of riparianareas and the water system, soil use planning

Excavation of water retention basins (sectors A and B)

for defence purposes, ground stabilization andconsolidation as well as the recovery of riparian

Recovery of the hydro-geological equilibrium –riverbed recovery

Recovery of the sinuosity and length of watercourses

areas, even degraded ones, by allocating them Reduction of artificiality (i.e. transversal works)to recreational uses” (paragraph 3, Art. No. 1of the Operating Instructions

Recovery of hydro-geological equilibrium.Reduction of flood speed

Widespread natural reforestation (sectors A and B)

Arboriculture for extensive wood production throughautochthon speciesForestation through autochthon species for biomassproductionReforestation and reshaping of the embankment flood bed(naturalistic engineering techniques)

Recovery of the self-purifying capacity Widespread reforestation (sectors A and B)Buffer zoneDevelopment of “filter ecosystems” (sector B)

Preservation of biodiversity and recovery of theenvironmental continuity

Increase and consolidation of ecological network nodes

Actions aimed at preserving habitat or species on the basisof a priority rankingActions aimed at monitoring invasive speciesCreation of biological corridors (of species-specific)

Improvement of the carbon cycle Development of units the purpose of which would be toact as “carbon sinks”, able to produce renewablebiomasses

Environment and landscape reconditioning Restoration of historical construction worksEnvironmental recovery for didactical and enjoymentpurposes

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REFERENCES

Altan M.G.B., Castellarin B., Fantin E., Foramitti R., Romanin F., Turoldo D.M., (1990), Le alluvionidel Tagliamento a Latisana e nei comuni della bassa friulana, Ediz. “La Bassa”-collana/12.

Arscott, D. B., K. Tockner & J. V. Ward (2000), Aquatic habitat diversity along the corridor of anAlpine floodplain river (Fiume Tagliamento, Italy). Archiv für Hydrobiologie 149: 679-704.

Arscott D. B., Tockner K. & J. V. Ward, (2001), Thermal heterogeneity along the corridor of an Alpinefloodplain river (Fiume Tagliamento, Italy). Can. J. Fish. Aquat. Sci. 58: 2350-2373.

Autorità di bacino dei fiumi Isonzo, Tagliamento, Livenza, Piave, Brenta-Bacchiglione (1997), Piano dibacino del fiume Tagliamento. Piano stralcio per la sicurezza idraulica del Medio e basso corso”.

Bacci M., Nardini A. (2000), Dalla valutazione di impatto ambientale alla valutazione integratapartecipativa, Ed. Cantagalli, Siena.

Castellarin B., (1988), Il Tagliamento: il fiume, le piene, le difese, Società Filologica Italiana, Udine: 81-94.

Fusco Girard L., Nijkamp P. (1997), Le valutazioni per lo sviluppo della città e del territorio, Angeli,Milano.

Edwards, P.J., Kollmann, J., Gurnell, A.M., Petts, G.E., Tockner, K. & Ward, J.V. (1999), The role ofisland dynamics in the maintenance of biodiversity in an Alpine river system, Bulletin of GeobotanicalInstitute, Research Project ETH.65. 73-86.

Egli T., (2000),. Non Structural Flood Plain Management. Measures and their Effectiveness,International Commission for the Protection of the Rhine (ICPR).

Gurnell, A.M., G.E. Petts, D.M. Hannah, B.P.G. Smith, P.J. Edwards, J. Kollmann, J.V. Ward and K.Tockner. (2000), Wood storage within the active zone of a large European gravel-bed river.Geomorphology 34: 55-72.

Gurnell, A.M., Petts, G.E., Harris, N., Ward, J.V., Tockner, K., Edwards, P.J. & Kollmann, J. (2000),Large wood retention in river channels: The case of the Fiume Tagliamento.

Gurnell, A.M., G.E. Petts, D.M. Hannah, B.P.G. Smith, P.J. Edwards, J. Kollmann, J.V. Ward and K.Tockner (2001), Island formation along the gravel-bed Fiume Tagliamento, Italy. Earth SurfaceProcesses and Landforms 26: 31-62.

Lapini L., Dall'Asta A., Bressi N., Dolce S.& Pellarini P., (1999), Atlante corologico degli anfibi e deirettili del Friuli - Venezia Giulia. Edizioni del Museo Friulano di Storia Naturale, Comune di Udine, 43,Udine.

Lapini L., Dall'Asta A., Dublo L., Spoto M. & Venier E., (1995), Materiali per una tereiofauna dell'Italianord-orientale (Mammalia, Friuli - Venezia Giulia). Atti del Museo Friulano di Storia Naturale. InGortania, 17, Udine.

Lichfield N. (1996), Community Impact Evaluation, University College Press, London.

72

Müller, N. (1995), River dynamics and floodplain vegetation and their alterations due to human impact.Arch.Hydrobiol.Suppl. 101: 477-512.

Perco F., Cassetti P.& Utmar P., (2000), Cormorani e Marangoni in Italia e nel Friuli - Venezia Giulia(Aves, Phalacrocoracidae). Atti del Museo Friulano di Storia Naturale. In Gortania, 22, Udine.

Petti M. (30 aprile 2003), Simulazione di esondazioni fluviali mediante tecniche ai volumi finiti,relazione presentata al Convegno “Rischio idraulico ed idrogeologico. Studi e prospettive operative”,CIRM – Provincia di Udine, Udine.

Poldini L., (1991), Atlante corologico delle piante vascolari nel Friuli - Venezia Giulia. Università deglistudi di Trieste, Trieste.

Schlaepfer D.R., Rotach A. (2003), Rapid expansion-contraction dynamics and Ecosystem-Processes ina large intermittent floodplain river (Tagliamento, NE-Italy), Diplomarbeit, Swiss Federal Institute forEnvironmental Science and Technology (EAWAG), Dübendorf, Switzerland.

Spaliviero M. (2002), Historic fluvial development of the Alpine-foreland Tagliamento River, Italy andconsequences for floodplain management, Geomorphology 1277 (2002), 1-17.

Stefanini S., Gerdol S. Stefanelli A. (1979), Studio per la definizione dei pericolo naturali nella RegioneFriuli Venezia Giulia (alluvioni, mareggiate, frane e valanghe), Regione Autonoma Friuli Venezia GiuliaAssessorato dell’Agricoltura, Foreste, Economia montana, Direzione regionale delle Foreste.

Stoch F., Paradisi S. & Buda Dancevich M., (1992), Carta Ittica del Friuli - Venezia Giulia. ETP, Udine.

Tockner, K. & Stanford, Jack, A. (2002), Riverine flood plains: present state and future trends.Environmental Conservation 29 (3): 308-330.

Tockner, K. & J. V. Ward (1999), Biodiversity along riparian corridors. Archiv für Hydrobiologie,Supplement 115/3: 293-310.

Tockner, K., Paetzold A., Karaus U. (2002), Leben in der Flussdynamik zwischen Trockenfallen undHochwasser, “Katastrophe oder Chance? Hochwasser und Ökologie” 37-47, Verlag Dr.Friedrich Pfeil,München.

Tockner, K., F. Malard & J.V. Ward (2000), An extension of the Flood Pulse Concept. HydrologicalProcesses 14: 2861-2883.

Tockner, K., J.V. Ward, D.B. Arscott, P.J. Edwards, J. Kollmann, A.M. Gurnell, G.E. Petts and B.Maiolini. (2003), The Tagliamento River: A model ecosystem for Alpine gravel-bed rivers.Aquatic Sci.65: 239-253.

Tockner, K., Klaus, I., Baumgartner, C. & J.V. Ward. Amphibians in a dynamic gravel-bed river.J.Appl.Ecol. submitted.

Todini E., Bossi A. (1986), PAB (Parabolic and Backwater) an unconditionally stable flood routingscheme particularly suited for real time forecasting and control - Journal of Hydraulic Research, Vol.24, n. 5.

Todini, E. and Bottarelli, M. (1997), ODESSEI: Open architecture DEcision Support System forEnvironmental Impact: Assessment, planning and management. In Operational Water Management,Refsgaard & Karalis (eds), Published for EWRA by Balkema, Rotterdam, Brookfield, 229-235.

73

Ufficio federale delle acque e della geologia (UFAEG) (2001), Protezione contro le piene dei corsid’acqua, Dipartimento federale dell’ambiente, dei trasporti, dell’energia e delle comunicazioni, Berna(CH).

Various Authors, (September 2003), Best practices on flood prevention, protection and mitigationWater Framework Directive Common Implementation Strategy.

Various Authors, (30 November – 1 December 2002), International Conference on prevention offlood hazards by integrating socio-economic and environmental conditions, Budapest Initiative onstrengthening international cooperation on sustainable flood management Budapest.

Verdesca D. (2003), Manuale di valutazione d’impatto economico-ambientale, Maggioli, Sant’Arcangelodi Romagna.

Vescia M. (2003), Analisi delle ipotesi d’intervento per la laminazione delle piene nel medio e bassocorso del fiume Tagliamento, Tesi di laurea, Univ. Degli Studi di Bologna, Facoltà d’Ingegneria, corsodi Laurea in Ingegneria Civile – Indirizzo Idraulica, anno accademico 2002/03.

Ward J.V., Tockner, K., Uehlinger U., Malard F. (2001), Understanding natural patterns and processesin river corridors as the basis for effective river restoration. Regulated Rivers: Research and Management17:311.323.

WWF (2002), Managing Floods in Europe: the Answers already Exist, more intelligent river basinmanagement using wetlands can alleviate future flooding events, WWF Background Briefing Paper.

WWF (2002), a cura di N. Toniutti e A. Agapito Ludovici, Tagliamento fiume d’Europa. Il problemadelle casse di espansione, WWF Italia.

WWF (2002), Living with the River, Life-Nature project in the Tisza floodplain, WWF Hungary.

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