Activity report

MOLINES: Modelação da inundação em estuários. Da avaliação da

perigosidade à gestão crítica

PTDC/AAG-MAA/2811/2012

PLANNING GUIDELINES AND FLOOD ALERT BULLETINS FOR SEIXAL

AND THE TAGUS ESTUARY

Pedro Pinto

March 2016

Funding:

Table of Contents

Introduction ..................................................................................................................................... 3

Framework .................................................................................................................................. 3

Objectives .................................................................................................................................... 3

Other activities ............................................................................................................................ 3

Compilation of Planning Guidelines ................................................................................................ 3

Territorial management tools ..................................................................................................... 4

Planning Guidelines ..................................................................................................................... 4

Flood Risk Management Guidelines and Dissemination ................................................................. 8

Alert Bulletin for the Seixal Bay ................................................................................................... 8

Alert Bulletins for the Tagus Estuary and the West Coast of Portugal ...................................... 10

References ..................................................................................................................................... 15

3

INTRODUCTION

Framework

This report describes the work performed by the Research Fellow Dr. Pedro Pinto (Chave de Associação

de Bolseiro FCT: J0248817N5Y) under a 3 month research grant of the project MOLINES - Modelação da

inundação em estuários. Da avaliação da perigosidade à gestão crítica (PTDC/AAG-MAA/2811/2012), in

the National Laboratory of Civil Engineering (LNEC). That activity took place between Nov 23rd 2015 and

Feb 22nd 2016, supervised by Dr. Paula Freire of the Estuaries and Coastal Zones Division (NEC) and Dr.

Anabela Oliveira of the Information Technology in Water and Environment Research Group (GTI), of the

Hydraulics and Environment Department (DHA) of LNEC.

Objectives

The objectives were:

Helping fulfill Task 12 of the Molines Project, regarding the compilation of planning guidelines.

Collaborate with the MOLINES Team in completing ongoing tasks regarding the Flood Alert System and other instruments of communication and outreach.

Attend and participate in meetings with stakeholders and project partners.

Other activities

As part of the MOLINES Team, the Fellow attended the workshop Gestão de Cheias em Ambientes Estuarinos (November 12th), and took part in a meeting (January 8th) with the Seixal Civil Protection, and a meeting (February 18th) with the ANPC. The Fellow integrated an organized field trip to Loures, Vila Franca de Xira and Lezíria Grande do Tejo and conducted five other short visits to sites around the Tagus Estuary.

COMPILATION OF PLANNING GUIDELINES As part of Task 12, the Fellow compiled a set of possible adaptation actions for the urban riverfront of

Seixal, based on relevant literature and field observation. These actions were divided into structural-

/non-structural measures, and further sub-divided into “hard/grey”, “green” and “soft” adaptation

actions. A sub-set of 19 actions was them selected as viable and recommended actions to be

implemented locally. These actions range in scope (from small actions at the dwelling scale to large,

region-wide policy shifts or improvements to the legal framework), in the time horizon expected for

their full implementation (some have already been implemented or could be within a couple of years,

others would require a generations’ time or more to be concluded), and in the costs involved. The

actions are equally characterized on the level of “regrets” they entail. Some actions, and especially those

garnering multiple benefits and flood protection with existing conditions, are considered of low- or no-

regrets. Others, would only be of real use if expected scenarios of sea-level rise come to be, and would

be either wasteful or would be of negative impact if not. These are high-regrets actions, and should be

avoided while there is a significant level of uncertainty over the timeframes of sea-level rise. A brief

description of these actions, as well as two tables listing them, is presented below. These guidelines are

4

to be included in one of the Project’s peer-reviewed papers, “A local scale approach to estuarine flood

risk management”, to be submitted to Natural Hazards.

Territorial management tools

In recent decades, municipal land-use management and planning has been vastly improved through the

implementation of mandatory municipal land-use plans (PDMs) and the introduction therein of several

National, Regional, and Local theme maps and strategies. In their latest revision, they are now required

to include risk maps, which highlight the territorial vulnerability associated with natural and

technological hazards. Flood-prone areas are equally required to be transposed into zoning and building

restrictions as part of the National Ecological Reserve. While this has been mandatory since 1990, the

technical requirements and methods have been recently improved to reflect the transposition of the

Floods Directive (Directive 2007/60/EC) into national law.

These changes, implemented ultimately at the municipal level, often derive from indications emanating

from regional plans or national strategies. With great interest to the Seixal waterfront and the Estuary as

a whole, are the Regional Land-Use Plan (PROT-AML) and the Estuary Management Plan (POET). Both

are pending final approval, but some of the measures therein are already being recommended by the

Regional Coordinating Commission (CCDR) and the Portuguese Environmental Agency (APA), both

central government agencies. Other sectorial plans, such as the Natura 2000 Plan, the Tagus River Basin

Management Plan, or the Natural Reserve Management Plan, require incorporation into municipal

planning, but their influence over local decision-making is less pronounced in the case of Seixal.

Municipal emergency planning deserves a separate document (Seixal’s latest Emergency Plan was

approved in 2014 and is targeted mostly at emergency response and coordination among civil

protection agents).

Planning Guidelines Risk avoidance from coastal flooding is becoming an increasingly difficult task. Urban waterfronts are

coveted by real-estate agents, as the value of prime-locations and views over the estuary come at a

premium. Former industrial and port areas present unique opportunities for centrally-located urban

development (ULI 2004; Brown 2008). At the same time, sea-level is rising and posing an ever-increasing

threat to urbanized shorelines and natural systems (Hallegate 2013; Fitzgerald 2008; Nicholls 2010).

Wetlands are now increasingly “squeezed” (Torio 2013; Kirwan 2013) between rising sea waters and

encroachment by flood defence infrastructures. While passive flood risk management has been

appropriate in some contexts, future challenges will demand a more pro-active adaptation stance.

In selecting the recommended planning guidelines for the Seixal waterfront, the MOLINES Team

identified a set of 26 possible adaptation actions (Table 1) that are being considered in the context of

urban waterfronts., from relevant literature (FLOODsite 2009; EEA 2013; Gersonius 2008; Wilby 2012;

Hallegatte 2009; Hamin 2009; Poussin 2012; Arkema 2013; CCAP 2011) and observation of local

conditions along the Tagus Estuary, during six visits to sites in Seixal, Almada, Vila Franca de Xira, Loures,

Oeiras, Alcochete, and Lisbon.

5

Table 1 – List of adaptation actions to coastal flooding and sea-level rise

The actions were separated into two main classes, based on whether structural interventions were

required. Although definitions vary, we take the simplest of definitions: “structural” actions require

Low High Small Large Short Long No/Low HighH

1 Equip vulnerable dwellings with removable, fixed, or automatic

flood gates for doors, windows, airholes and garage doorsX X X X

H2 Implement formal system of road signs

providing warning of flooded roadways and sidewalksX X X X

H3 Waterpumps must be installed on all basements,

underground garages, or ground floors below flood stageX X X X

H4 Transfer machinery, generators,

elevator shafts to higher floorsX X X X

H5 Improve stormwater drainage systems by replacing pipes,

introducing tidal vales, pumping stations or reservoirsX X X X

H6 Transfer schools, health facilities, firehouses, and other

civil protection agencies located on vulnerable areasX X X X

H7 Raise waterfront parapets/guards to increase

protection against low flood levels or wave spill-overX X X X

H8 Raise waterfront public spaces and/or design them

so as to double as barriers against floodingX X X X

H9 Rebuild with raised ground floors or on stilts,

with elevated pathways and driveways, above flood stageX X X X

H1

0 Abandon most vulnerable areas, moving

buildings, people and functions to safe locationsX X X X

H1

1 Create or upgrade dykes and

levees protecting vulnerable shorelinesX X X X

H1

2 Create flood barrier/dam

across river's mouthX X X X

G1 Actively manage existing wetlands so as to

increase their resilience and promote their expansionX X X X

G2 Reduce peak surface runoff by introducing green

infrastructure and improving infiltration and detentionX X X X

G3 Maintain beach nourishment projects

to reduce the impacts of coastal erosionX X X X

G4 Create new artificial wetlands, namely by

reconverting underused reclaimed landfill areasX X X X

G5 Protect existing wetlands,

beaches and dune systemsX X X X

S1 Identify safe routes alternative to

flood-vulnerable roadways and transit linesX X X X

S2 Forbid the construction of

basements in flood-prone areasX X X X

S3 Remove valuable or perishable items and sensitive

infrastructure from basements and flood-prone ground floorsX X X X

S4 Map risks, highlight vulnerable

areas, and increase awarenessX X X X

S5 Forbid new construction in vulnerable

areas through local planning instrumentsX X X X

S6 Raise awareness of politicians, civil protection agents, and

populations to the impacts of coastal flooding and sea-level

rise

X X X X

S7 Revise building standards so as to require higher

ground floor clearance on new buildings or reconstructionsX X X X

S8 Implement early flood warning and monitoring

systems (SMS, Media alerts, Sirens…)X X X X

S9 Enact changes to flood risk insurance policies so as to

increase accountability for "risky" location choicesX X X X

So

ft

No

n-S

tru

ctu

ral

Cost Time horizon RegretsScale

Str

uc

tura

l

Ha

rdG

ree

n

6

physical implementation, where “non-structural” rely solely on natural evolution of systems or require

no physical action. Another division is made between “grey”, “green”, and “soft” actions. Here, we

follow the definition of the European Environmental Agency (EEA 2013). “Grey”, also called “hard”

actions, are technological and engineering solutions, such as building or upgrading coastal defences or

reinforcing buildings; “green” actions center on the promotion of benefits from natural systems

(ecosystem-based), such as the protection and expansion of wetland areas to act as buffers against

storm-surge; “soft” actions are management and planning policy options, or new legal directives,

targeted at reducing risk exposure or promote a steady increase in the overall resilience of communities.

Examples would include forbidding new construction in vulnerable areas or making alterations to flood

insurance policies to increase accountability for location choices.

The 26 actions are then qualified according to their cost (low to high), the scale of intervention/scope

(small/dwelling, to large/regional or national scale), the time horizon for full implementation (from

short/less than 2 years to long/over 25 years), and regrets (No regrets being solutions that will provide

benefits regardless of whether flood risk increases, whereas high regrets solutions are those that, if

implemented, would adversely impact other measures of environmental performance or be too costly

to revert.

The rating of each action is derived from the team’s experience with the Seixal/Tagus Estuary situation,

and is naturally subjective and context-dependent. For instance, some “soft” adaptation actions are

relatively easy to approve in Portuguese legislature, once there is enough public/political support for

them. In other contexts, such as in the United States of America, change or updating legal documents

may be a much more strenuous effort, especially when land rights are involved (Eichenberg 2013,

Davoren 1982). At the same time, some more costly structural measures would likely face serious

financing constraints given Portugal’s economic hardship.

Based on these ratings and how adequate/easy to implement they would be for the specific context of

Seixal, we selected a set of actions that we would recommend as steps in increasing the resilience in

face of coastal flooding and future sea-level rise (Table 2).

Some of the actions indicated have already been completed (the Municipal Land Use Plan of 2014, for

instance addresses the delimitation of vulnerable areas, limited the construction of basements, and

expanded the protection of wetlands), while other actions (such as the remodelling of waterfront public

spaces so as to provide flood protection) would require future action. While quite a few of the actions

(1-11) address problems already experienced during exceptional storm-surges, others (12-19) should be

part of a long-term strategy to minimize the impacts of expected sea-level rise. All but 4 of the actions

are considered as no- or low-regret, that is, they provide multiple benefits and/or are beneficial even if

the more adverse impacts of climate change do not materialize.

7

Table 2 – Selection of adaptation actions to coastal flooding and sea-level rise in the municipality of Seixal

Time

horizon Cost Scale Regrets

Implemented

in Seixal? Agents

1

Equip vulnerable dwellings with removable,

fixed, or automatic flood gates for doors,

windows, airholes and garage doors

1-2 yrs Low Dwelling Low No

Homeowners, storeowners

(installation), Municipality

and parishes (supervision)

2

Implement formal system of road signs

providing warning of flooded roadways and

sidewalks

1-2 yrs Low Dwelling Low No

Municipality (installation),

civil protection agents

(supervision)

3Protect existing wetlands, beaches and

dune systems1-2 yrs Low City/Region No Yes

Municipality (planning

instruments), Environment

Agency (management)

4Identify safe routes alternative to flood-

vulnerable roadways and transit lines1-2 yrs

Low/

MediumBlock No Partially

Municipality, civil protection

agents, public transit

companies

5Forbid the construction of basements in

flood-prone areas3-10 yrs Low Dwelling Low Yes Municipality

6Forbid new construction in vulnerable

areas through local planning instruments3-10 yrs Low Neighborhood Low Partially Municipality

7

Remove valuable or perishable items and

sensitive infrastructure from basements

and flood-prone ground floors

3-10 yrsLow/

MediumDwelling Low Partially

Homeowners, storeowners

(implementation),

Municipality (supervision)

8

Waterpumps must be installed on all

basements, underground garages, or

ground floors below flood stage

3-10 yrsLow/

MediumDwelling Low No

Municipality, homeowners,

storeowners

9

Implement early flood warning and

monitoring systems (SMS, Media alerts,

Sirens…)

3-10 yrsMedium/

HighCity/Region Low Partially Civil Protection Agents

10

Actively manage existing wetlands so as

to increase their resilience and promote

their expansion

3-10 yrsLow/

MediumNeighborhood No No

Environment Agency

(planning/ managing),

Municipality (assistance)

11Map risks, highlight vulnerable areas, and

increase awareness3-10 yrs

Low/

MediumBlock No Yes Municipality

12Transfer machinery, generators, elevator

shafts to higher floors3-10 yrs

Medium/

HighDwelling Medium No

Homeowners, storeowners

(installation), Municipality

(supervision)

13

Improve stormwater drainage systems by

replacing pipes, introducing tidal valves,

pumping stations or reservoirs

10-25 yrsMedium/

HighNeighborhood Low Partially Municipality

14

Raise waterfront parapets/guards to

increase protection against low flood levels

or wave spill-over

10-25 yrsLow/

MediumNeighborhood Medium No Municipality

15

Raise waterfront public spaces and/or

design them so as to double as barriers

against flooding

10-25 yrsMedium/

HighBlock Medium No Municipality

16

Reduce peak surface runoff by introducing

green infrastructure and improving

infiltration and detention

10-25 yrsMedium/

HighNeighborhood Low No

Municipality (planning,

major features),

homeowners, parishes

17

Enact changes to flood risk insurance

policies so as to increase accountability

for "risky" location choices

10-25 yrs High City/Region High No Central Government

18

Revise building standards so as to require

higher ground floor clearance on new

buildings or reconstructions

+25 yrs Low Neighborhood Low No Municipality

19Create new artificial wetlands, namely by

reconverting underused reclaimed landfill

areas

+25 yrs High City/Region Low NoBaía do Tejo Society/

Environment Agency

South Bay" project,

Action

8

FLOOD RISK MANAGEMENT GUIDELINES AND DISSEMINATION

Alert Bulletin for the Seixal Bay As part of the Flood Risk Management Guidelines and Dissemination, the Fellow helped create the

“Boletim de Alerta de Inundação Estuarina para a Baía do Seixal”, in close collaboration with the Molines

Team, the Proteção Civil do Seixal and ANPC. This system of communication conveys information on

conditions favourable to the occurrence of risk related to estuarine flooding, triggered by the Molines

forecast system based on a highly-accurate circulation model run daily at LNEC. The recipients are the

civil protection agents in Seixal as well as the national authority. It was conceived as a concise (one-page

long), easy to interpret, alert information vehicle. It includes information on the hour and level of alert

for each of the Critical Points analyzed by the Molines forecast system.

The Molines forecasting system was setup in previous tasks to automatically produce as outputs the

water elevation around the Seixal Bay. Several critical points were equally selected based on their high

vulnerability to estuarine flooding. For each of these points, the elevation difference between the street

level, along the waterfront, and the expected water level is automatically computed. Whenever a

certain elevation threshold is exceeded, a flood alert is triggered. Depending on how high the water is

expected to rise, the alert level increases.

The bulletin was thus setup so as to convey in a clear and precise manner the alerts triggered by the

model. The recipients are, in a first stage, the civil protection agents in the municipality of Seixal. The

configuration of the Bulletin went through several iterations, with three main aspects being paramount

to its creation:

It had to be consistent with the precision levels and trusted outputs of the Molines model;

The Bulletin had to be easily implemented as an automatic routine within the daily

forecasting/modeling computation procedures;

It needed to be suited to be readily available, understandable, and useful to actors with

different levels of expertise and knowledge of the forecasting system.

The final output needed to be generated as a pdf or similar format, so as to be easily transferred

and accessible to agents outside LNEC and/or without direct access to the Molines webpage.

The final version of the Bulletin (Figure 1) was approved after meetings with Seixal’s Civil Protection and

the ANPC, and following extensive revision and active contributions from several members of the

Molines Team, especially Dr. Paula Freire, Dr. Anabela Oliveira, Dr. André Fortunato, as well as the two

main programmers of the outreach platform, João Gomes and João Rogeiro.

9

Figure 1 – Alerta de Inundação Estuarina – Baía do Seixal

10

Alert Bulletins for the Tagus Estuary and the West Coast of Portugal

Based on the Seixal Bulletin, and resorting to the modeling capacities already developed by the Molines

Team, another communication tool was conceived: the “Boletim de Alerta de Inundação – Estuário do

Tejo” (Figure 2). This alert bulletin conveys similar information to that of the Seixal Alert, but this time

for a selection of Critical Points surrounding the whole Tagus Estuary.

The selection of Critical Points was made through an iterative process of identification of points for

which the most number of occurrences in separated events were registered. For this process, the Fellow

used the database and GIS project developed by Ana Rilo, also developed in the Molines Project.

Through the analysis of 18 storm events (since 1941) which registered multiple occurrences, three

different types of forcing factors were isolated as dominant causes of flooding in low-lying estuarine

shorelines (Figure 2):

“Green” occurrences are mostly associated with intense precipitation over small watersheds,

with subsequent drainage issues provoking urban flooding in the lower end of the valleys.

“Blue” occurrences are associated to events where the discharge of the Tagus River, just

upstream of its Estuary, was exceptionally high;

“Red” occurrences were those where storm surge and/or high winds can be isolated as the

principal cause for flooding along the Estuary’s margins.

Figure 2 – Analysis of Past Estuarine Flood Events

11

While most events will result of a combination of these factors, the selection of critical points took into

account especially those where storm surge/exceptional estuarine water levels could be isolated as a

dominant trigger of flooding. Further analysis of the events and locations of occurrences allowed for a

first selection of 19 critical points (Figure 3).

Figure 3 – Pre-selection of Critical Points based on the Analysis of Past Estuarine Flood Events

Following site visits to Seixal, Cova da Piedade, Cacilhas, Cova do Vapor, Trafaria, Vila Franca de Xira,

Ponta da Erva, Parque das Nações, Cais do Gás, Terreiro do Paço, Alcântara, Dafundo, and Cruz

12

Quebrada, the critical points were narrowed to 11, plus an offshore “virtual buoy” for monitoring

conditions at the Harbours entrance.

The final version of the Estuary Bulletin includes additional information on atmospheric conditions in the

Tagus Estuary/Lisbon Region, as well as information on the expected wave height, also extracted from

the Molines model (Figure 4).

This tool is proposed to fit the needs of civil protection agents, municipalities, and a select group of

entities such as the Administração do Porto de Lisboa (APL) (Port Authority), Associação de Beneficiários

da Lezíria Grande de Vila Franca de Xira (ABLGVFX) and Reserva Natural do Estuário do Tejo (RNET). It

includes a couple of additional elements regarding the meteorological conditions for the Estuary so as to

increase its usefulness for a greater number of stakeholders.

With a similar layout and drawing from the experience of both these bulletins, the prototype for a third

bulletin, “Alerta de Condições do Mar” (Figure 5) was equally produced. It is based on the outputs of

LNEC’s Water Information Forecast System application for the Portuguese coast, based on high

resolution wave propagation and storm surge models (http://ariel.lnec.pt). All three Alert bulletins were

presented to, and well-received by, the ANPC and Civil Protection of Seixal, and could spur further

developments within the “Sistema Nacional de Proteção Civil”, in case the ANPC so wishes.

13

Figure 4 – Alerta de Inundação Estuarina – Estuário do Tejo

14

Figure 5 – Alerta Condições do Mar – Costa Ocidental

15

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