Understanding the tides crucial for joint management of the Scheldt Estuary ..................................... 4

From stakeholder to shareholder – organising stakeholder commitment for the Scheldt estuary of the future ................................................................................................................................................ 5

A smooth Scheldt .................................................................................................................................... 6

Keynote 4 - Nature-based Flood Defences: panacea or illusion ............................................................ 7

Using natural foreshores instead of traditional dike re-enforcements: a field pilot in the large shallow lake Markermeer, the Netherlands .......................................................................................... 8

Towards a consistent suite of models for flood risk management ....................................................... 9

Numerical study of flow and turbulence through submerged vegetation .......................................... 10

Human versus natural mud fluxes in the Scheldt estuary: are they significant and if so, how can they best be optimised? ............................................................................................................................... 11

River-induced flushing of the turbidity maximum in narrow estuaries ............................................... 12

Suspended sediments over silt-sand mixtures under waves ............................................................... 13

The new Delta Flume for large-scale physical model testing. ............................................................. 14

Wave attenuation over the Great Barrier Reef matrix ........................................................................ 15

Pilot Application of Delft3D Flexible Mesh: Assisting a Field Campaign at the Sand Engine .............. 16

Sustainability of the multi-channel system in the Westerschelde under influence of dredging and disposal ................................................................................................................................................. 17

Simulation of long-term morphodynamic behaviour of the Western Scheldt .................................... 18

Modeling the morphodynamics of the mouth of the Scheldt estuary ................................................ 19

Land subsidence: the flooding threat in coastal cities, a case study in Ho Chi Minh city ................... 20

Establishing a sediment budget in the ‘Kleine Noordwaard’ area of the Biesbosch inland delta ...... 21

Delta Alliance - for the resilience of deltas worldwide ........................................................................ 22

Dutch results of Pro-Tide a NWE-Interreg project on Developing, Testing and Promoting Tidal Energy in coastal and estuarine zone ................................................................................................... 23

Determining accurate weir discharge-water level relationships via CFD ............................................ 24

Predicting flooding events on gravel coasts ......................................................................................... 25

RISC-KIT: Resilience-Increasing Strategies for Coasts – toolkit ............................................................ 26

Towards a nonlinear meander evolution model .................................................................................. 27

Land subsidence, sea level rise and urban flooding: coping strategies in coastal cities ..................... 28

Development of coastal-FEWS: early warning system tool development .......................................... 29

Operational wave forecasts in the southern north sea ....................................................................... 30

Towards time and space evolving extreme wind fields ....................................................................... 31

Validation of SWAN under extreme conditions in the Wadden Sea ................................................... 32

Global-scale modelling of sea level extremes to estimate coastal flood risk ...................................... 33

Modelling River Dunes in the Rhine Branches Under Extreme Floods ................................................ 34

Estuarine Mangrove Squeeze In The Mekong Delta ............................................................................ 35

Batumi coastal protection: facing decreasing river discharges of gravel and canyons traps ............. 36

Transferability and parameter uncertainty of hydrological models for estimating future mean and extreme discharges in the context of climate change ......................................................................... 37

Sustainable ports development concept as adaptive, environmental and socio-economic growth .. 38

Modeling of wave attenuation by vegetation with XBeach................................................................. 39

FIeld measurements - do they provide the ground truth? .................................................................. 40

Wave growth at short fetches .............................................................................................................. 41

Predicting wave-induced loads on a moored ship with a non-hydrostatic wave-flow model ............ 42

Coupling a near field outfall model with a far field hydrodynamic model .......................................... 43

Transition structures in grass slopes of primary flood defences tested with the wave impact generator .............................................................................................................................................. 44

A European flood risk model and its use for analyzing climate change adaptation strategies ........... 45

On the set-up of field research in sumps of wastewater pumping stations ....................................... 46

Preventing salt intrusion through shipping locks: recent innovations and results from a pilot setup47

Bubble plume towed in salt-stratified water ....................................................................................... 48

Water – air bubble screens reducing salt intrusion through ship locks .............................................. 49

Laboratory studies on the response of fine sediment to wind ............................................................ 50

Numerical simulation of flow and sediment transport dynamics on the Magdalena River section of Barrancabermeja-La Coquera (Colombia). ........................................................................................... 51

Hydraulic modeling of Magdalena River using SOBEK ......................................................................... 52

SWAN’s underestimation of long wave penetration into coastal systems ......................................... 53

Long waves in intermediate depths and their influence on the design of nearshore terminals ........ 54

Three-dimensional Arabian Gulf Hydro-Environmental Modeling using Delft3D ............................... 55

Computational Fluid Dynamics of a bubble curtain for the prevention of salt intrusion at sea locks 56

Development of a numerical model to predict the erosion of a dike after the failure of the

revetment using time dependent boundary conditions ...................................................................... 57

Developing a transport model for plastic distribution in the North Sea ............................................. 58

Extreme value analysis in typhoon prone areas: case study of the Pearl River estuary ..................... 59

Comparison between the operation of a prototype and a model pump ............................................ 60

Numerical modelling of the impact of Sea level rise on large tidal inlet/basin systems .................... 61

Open ports for container vessels ......................................................................................................... 62

On the (in)applicability of ANSI/HI 9.8-2012 guidelines at wastewater sump design ........................ 63

Discussion on the acceptance criteria for physical model testing of intake pumping stations .......... 64

Morphological evolution of Yangtze Estuary on decadal-scale and its response to human interference .......................................................................................................................................... 65

Monitoring the impacts of floating structures on the water quality and ecology using an underwater drone ..................................................................................................................................................... 66

The 2013 Xaver storm surge and the resilient response of the North Sea defence system ............... 67

Sharing research data of the sand motor with the openearth datalab ............................................... 68

Using water age to quantify the hydrodynamic circulation in Lake Taihu using D-Flow Flexible Mesh .............................................................................................................................................................. 69

Sensitivity of the Sobek 2D Overland Flow Model to change in grid cell size ..................................... 70

Numerical and physical modelling of different nourishment designs ................................................. 71

Reshaping of realistic beach nourishments under high angle wave conditions ................................. 72

Wave–current interaction study along Gulf of Khmbhat, India ........................................................... 73

Effect of vegetation on floods: the case of the river Magra ................................................................ 74

Comparison of three bed form models to predict roughness for operational flood modeling .......... 75

Understanding the tides crucial for joint management of the Scheldt Estuary Marcel Taal 1, Youri Meersschaut 2, Gert-Jan Liek 3 1 Deltares 2 Flemish Authorities, Department of Mobility and Public Works, Maritime Access Division 3 Dutch Ministry of Infrastructure and the Environment, Rijkswaterstaat Zee en Delta The Scheldt estuary is situated in the Netherlands and Flanders/Belgium. Both countries collaborate in policy, management and research, as laid down in a treaty of 2005. Preservation of the ‘physical characteristics of the estuary’ plays an important role in formulating objectives, but it is still debated ‘what exactly should be preserved’. What exactly should be preserved’ has a diversity over the various places, as both actual values and driving forces are different along sites. A management plan in such detail is not available.

Recent research has shown which role the tidal intrusion has in these discussions. Tidal intrusion as (an indicator of the) objective for future policy (i) reflects a long term development, (ii) can be linked to changes within the estuary itself, including sediment management and (iii) can be evaluated easily, as for practically all user-functions the increase in tidal amplification is regarded as negative. As a conclusion we pose that we need to accept that from science alone we cannot expect an unambiguous answer when preservation of the ‘physical characteristics of the estuary’ is fulfilled.

From stakeholder to shareholder – organising stakeholder commitment for the Scheldt estuary of the future Stephanie Janssen 1, Gerald Jan Ellen 2, Marcel Taal 3 1 Deltares 2 Deltares 3 Deltares The Scheldt Estuary is of central importance to ports, an extremely valuable, unique and protected nature reserve and is located in an area that is intensively used by agriculture and offers many opportunities for the tourism industry. Moreover the Scheldt Estuary covers both Dutch and Flemish territory. Due to this multitude of functions, the Scheldt Estuary provides the stage for a broad range of stakeholders and (conflicting) interests. Especially in the past decades these diverging interests led to an extremely tense decision-making process and accompanying implementation. The EU Interreg project ‘Estuaries on the MOVE’ (EMOVE) has taken up the challenge of bringing stakeholders together and organizing bottom-up commitment in working towards a sustainable Scheldt Estuary of the future. The main ambition of EMOVE was to turn stakeholders into shareholders, meaning that parties obtain ‘ownership’ of a particular development or project. Crucial in the approach were: 1) generating a shared understanding of the Scheldt estuary – combining state-of-the-art knowledge on the physical and ecological functioning of estuary involving knowledge on tidal processes, sediment budgets, estuarine processes and more with the different perspectives stakeholders have on the estuary – by means of a ‘Group Decision Modelling’ method and 2) collectively formulating projects and organizing coalitions for these projects. The result of the approach was both successful and highly promising. Five different projects were formulated – ranging from a changing polder regime (‘wisselpolders’), to a cross-border nature reserve, environmental-friendly sediment techniques, silt agriculture and governance opportunities – supported by stakeholder coalitions involving a variety sectors. The applied methodology of bottom-up project formulation, combined with Group Decision Modelling provided fruitful ground for a future healthy and sustainable Scheldt Estuary of the future and moreover important lessons for organizing stakeholder commitment in sensitive decision-making environments.

A smooth Scheldt Jelmer Cleveringa 1, Marcel Taal 2 1 ARCADIS 2 Deltares The Scheldt estuary delivers important (ecosystem) services, as a shipping lane, a nature reserve and in the protection against flooding. Ongoing studies of various aspects of estuarine development are an essential element of the estuarine management and this study is one example from many, executed in cooperation between the Netherlands and Flanders. The bathymetry of the Western Scheldt, the Dutch part of the Scheldt estuary, is measured each year. The abundance of data allows for detailed analysis of the morphology at scales that range from the (sediment volume of the) entire basin to the evolution of individual tidal flats and small tidal channels. Additionally the interpretation of aerial photographs of the intertidal and supra-tidal environments provides detailed information on the abundance of bed forms (mega ripples). A decline in the number of small tidal channels – ebb- and flood chutes and channels that connect the main ebb- and flood channels, is observed throughout the Western Scheldt. The large number of small tidal flats have merged into a limited number of bigger entities, and the jagged edges of the flats have given way to almost straight water lines. The surface area of the inter-tidal flats that is covered with mega-ripple fields has decreased. The overall change is from an irregular distribution of inter-tidal flats with branching channels and shallow areas towards smooth tidal flats in between the main channels. Causes for the smoothing of the Scheldt have not yet been found. Hypotheses and explanation have to account for the distribution of the change throughout the Western Scheldt. Explanation on the scale comprise intrinsic pattern development and/or the closure of branching tidal basins. Changes in the propagation of the tidal wave are ruled out as an explanation, because these are more pronounced in the eastern reaches. Future research, including numerical modelling simulations may provide more insight in the underlying mechanisms. Estuarine management needs to incorporate the fact that the future Scheldt will be a smoother Scheldt. The present and future morphology of the tidal flats and small channels differs from past patterns. Values that are associated with this morphology have and will changed and it may require tailor-made measures to retain them.

Keynote 4 - Nature-based Flood Defences: panacea or illusion Bregje van Wesenbeeck 1 1 Deltares

Using natural foreshores instead of traditional dike re-enforcements: a field pilot in the large shallow lake Markermeer, the Netherlands Ellis Penning 1, Henk Steetzel 2, Jasper Fiselier 3, Marieke de Lange 4, Vincent Vuik 5, Jaap van Thiel de Vries 6, Robbin van Santen 7, Sonja Ouwerkerk 8 1 Deltares 2 Arcadis 3 Royal Haskoning DHV 4 Alterra Wageningen UR 5 HKV 6 Boskalis 7 Arcadis 8 HKV - Lijn in Water Increasingly, natural foreshores are seen as a valuable alternative for, or addition to conventional dikes. Natural foreshores consist of shallow zones and beaches with a gradual slope and a (near-) natural vegetation, e.g. freshwater reedbeds and wetlands, willow forests, salt marshes and mangroves. They create an additional protection against flooding and wave attack on the dikes or can even protect the dike completely from being attacked. Using wide beaches and dunes is common practice in the coastal flood defense of the Netherlands. This is so far not the case for the larger delta lakes in the Netherlands. The shorelines of these lakes are at present protected by dikes, some several centuries old and important cultural historic monuments. There are several locations where the use of a soft defense in considered for various reasons. One is to spare the older dikes which otherwise would have to be completely rebuilt because of problems with macroinstability. In some places a soft defense may offer a more cost-effective and also more flexible alternative. A soft defense along these larger lakes is however a novelty. Many processes work differently from those at the coast. There are no tides, wave length is much shorter and vegetation will play a larger role in shore line development. The design of these defenses and also the expectations regarding related maintenance can therefore not be based on experiences gained over the past centuries on the coastal dunes and beaches. In order to better understand the crucial aspects of designing, constructing and maintaining a natural, vegetated foreshore, a pilot is being carried out along the ‘Houtribdijk’ dike between Lake Markermeer and Lake IJsselmeer (the Netherlands). This dike needs reinforcement since it no longer complies with Dutch safety standards. The pilot was constructed in summer 2014, and consists of a 500 m long stretch of sandy foreshore along the dike. Monitoring takes place from 2014-2018 for aspects of hydrodynamic forcing, morphodynamics in relation to vegetation development. We will present the process of design, implementation and the monitoring results of the first year after implementation.

Towards a consistent suite of models for flood risk management Robert Slomp 1, Ferdinand Diermanse 2, Hans de Waal 3, Jan Stijnen 4, Jan Noort 5, ludolph wentholt 6 1 Rijkswaterstaat-WVL 2 Deltares, the Netherlands 3 Deltares, the Netherlands 4 HKV Lijn in Water, the Netherlands 5 STOWA 6 STOWA Consistent national flood-risk management is only possible if the tools to analyse and implement policy are consistent. However, policy tools, flood defence assessment tools, design tools, flood forecasting tools have different requirements for computation times, accuracy, and spatial and temporal scale. Another challenge is that the instruments commissioned by the national water authority (Rijkswaterstaat), or the regional water authorities (water boards) have been developed by different (sub)contractors. The responsibility for the national waters is with the national government, while the STOWA (the training and research organisation for the regional water authorities) and provincial governments are responsible for the regional water systems. Facing this problem, the national and regional water authorities greatly reduced the number of separate instruments and achieved a fairly well-organized set of instruments and data for some main types of analyses during the past years: • The same hydrodynamic models for water levels, and wave propagation are used. • In the last 5 years probabilistic instruments have been used to calculate hydraulic loads for both the national water systems (Hydra-model suite), and the regional water systems (PROMOTOR). • The instrument to assess the strength regional flood defences (DAM) has been used for policy analysis of the national flood defences (3600 km) as well. • Indicators for policy tools have been provided using these tools. The national and regional water authorities have to be flexible, and should be able to use, adapt, and expand the instruments to cope with new policy questions. However, there is a major drawback to keep developing new tools for every policy question: the danger of inconsistencies. Therefore the national water authorities aims at the development of reusable, common software components. Consistent models are important for long term and short term policy choices and the evaluation of measures, and for explaining the level of a flood alert. Inconsistency definitely costs money and may cost lives.

Numerical study of flow and turbulence through submerged vegetation

Hyung suk Kim 1, Moonhyeong Park 2, Mohamed Nabi 3, Ichiro Kimura 4 1 River and Coastal Research Division 2 River and Coastal Research Divsion 3 Deltares 4 Hokkaido University Vegetation elements obstruct the flow and considerably decrease the mean flow velocities compared to non-vegetation zone. The additional form drag exerted by vegetation significantly affect the velocity distributions, turbulence structures and Reynolds stress profiles, and thus influence sediment transport and water pollutant. Especially, unlike the flow through emergent vegetation, the flow through submerged vegetation creates relatively high velocity gradient and induces a strong shear layer near the top of the vegetation element. An understanding of flow structures and exchange of mass and momentum through submerged vegetation is essential to be successful river restoration. In this paper, we perform LES for open channel flows through submerged matrix cylinders which are regarded as rigid-submerged vegetation. The computational model solves the filtered Navier-Stokes equations on a Cartesian grid with local refinement and employs the ghost-cell immersed boundary method to deal with solid boundaries. The cylinders are explicitly handled by computational grids. First, to validate the present computational model, the computation is conducted on experimental configuration of Liu et al. (2008) who measured streamwise and lateral velocity profiles and turbulence intensities using lase Doppler velocimetry (LDV). A good agreement between computation and measurement is found. The effects on submergence ratio (water depth to vegetation height) and vegetation density are investigated. The presence of the streamwise velocity inflection results in a strong shear layer region near the top of the cylinders and creates high turbulence. The coherent structures are produced above and behind the cylinders and those intensities increase with increasing vegetation density. The large scale vortices, which are a main mechanism of momentum exchange between the vegetation layer and the out of vegetation, are generated above the vegetation and these penetration depths decrease with an increase in the submergence ratio and vegetation density. It is demonstrated that LES can capture large scale vortices originating at the top of vegetation and account for detailed instantaneous flow fields through submerged vegetation.

Human versus natural mud fluxes in the Scheldt estuary: are they significant and if so, how can they best be optimised? Thijs van Kessel 1, Gijsbert van Holland 2, Joris Vanlede 3 1 Deltares 2 IMDC nv 3 Flanders Hydraulics Research, Flemish Government The mud dynamics of the Scheldt estuary is governed, like other estuaries, by the interplay between tidal flow, freshwater discharge, marine and fluvial mud supply and local sources and sinks, notably mud flats. Human impacts on the mud dynamics can be either direct or indirect. Direct impacts are caused by harbour and fairway maintenance dredging (i.e. dredging vessels transporting mud from A to B), indirect impacts are caused by human modifications of the estuary such as increasing channel depth by capital dredging or reducing the area of tidal flats by land reclamation, thus modifying the natural flux. Using a process-based mud transport model of the Scheldt estuary, these impacts have been quantified by evaluating different scenarios representative for the present bathymetry and maintenance dredging procedure or with a modified bathymetry or modified dredging procedure. The focus of this presentation is on the dredging procedure, as this can more easily be modified on the short term than estuarine bathymetry (both a reversion of land reclamation and channel depth would have large consequences for the economical function of the Scheldt estuary). The results show that although the ‘human’ fluxes caused by maintenance dredging are typically small compared to natural gross fluxes, they are very significant compared to natural residual fluxes, notably in the narrower section of the estuary near Antwerp. Here more than half of the available mud is ‘second-hand’, i.e. it has been dredged from and released back into the estuary at least once. This implies that an optimisation of the dredging and release cycles, including the smart selection of release locations, offers the perspective of smaller human impacts, possibly even at lower costs. A down-estuary shift of release locations would be favourable, whereas the present practice is that dredged mud is regularly released up-estuary of the harbour or access channel from which it has been dredged. Also, a shift to locations closer tidal flats may interrupt the vicious circle between mud disposal and dredging by enhancing the accretion rate of these flats. However, the surface area of these flats has to be substantial to provide more than just a short-term solution.

River-induced flushing of the turbidity maximum in narrow estuaries Johan Winterwerp 1, Miguel de Lucas Pardo 2, Bas van Maren 3, Julila Vroom 4, Zheng Bing Wang 5 1 Deltares & TUDelft 2 Deltares 3 Deltares 4 Deltares 5 Deltares & TUDelft In three previous papers (Winterwerp, 2011; Winterwerp and Wang, 2013; Winterwerp et al., 2013), we have argue that the Loire and Ems River have evolved into their current hyper-turbid state in response to large-scale engineering works, such as narrowing, rectification and deepening, sometimes accompanied by redirection of fresh water as well. In this paper, we show how fine sediments can build up in a flood-dominant narrow estuary at low river flows. Under normal flow conditions, the balance between river-induced flushing and estuarine circulation forms an estuarine turbidity maximum at the head of the salinity intrusion. At low river flows, this dynamic equilibrium is disturbed by the effects of up-estuary transport by tidal asymmetry and sediment-induced drag reduction. This conclusion follows from numerical simulations with Delft3D on the fine sediment dynamics in a schematized model of the Upper Sea Scheldt, the tidal river upstream of Antwerp.

Suspended sediments over silt-sand mixtures under waves Peng Yao 1, Min Su 2, Zhengbing Wang 3, Changkuan Zhang 4, Yongping Chen 5, Marcel J.F. Stive 6 1 Delft University of Technology 2 Delft University of Technology 3 Delft University of Technology & Deltares 4 Hohai University 5 College of Harbor, Coastal and Offshore Engineering, Hohai University 6 Delft University of Technology Deposits on tidal flat area are generally the mixtures of clay, silt and sand. The different types of sediment bed (clay-silt-sand mixtures) will result in different sediment transport processes, affecting the morphological changes. As these fine materials are mainly transported in suspension, it is important to understand the mechanisms of suspended sediment transport. The sediment in a silty coast behaves different from that of a sandy coast and muddy coast. One of its distinctive characteristics is the formation of the high concentration layer (HCL) near bottom during the stormy weathers. Although this phenomenon is well known, the formation and transport mechanism is poorly understood. Historically, many theories have been proposed to describe the near bed sediment concentration for non-cohesive sediments, whether these formulations are suitable for the silt-enriched HCL is unclear. We conducted a series of flume experiments to explore this knowledge gap on the HCL of the silty coast. Two types of bed materials with different silt content are investigated. The present study mainly concerns the suspended sediment concentration under various wave conditions. Quasi-steady high concentration layer has been observed in a wide range of wave conditions for both sediment beds. Suspended sediment concentrations are measured using a transverse suction system. The concentration inside the HCL (lowest measuring point) varies from 3 g/l to 60 g/l. Then, several existing near bed concentration predictors are tested against the experimental data. The results show that the latest formula of Van Rijn (2007a; 2007b) can give the best overall fitting results and can be used as a predictor for silt classes after coefficient re-calibration. This study is the first step in a systematic investigation of morphological changes over silty tidal flats.

The new Delta Flume for large-scale physical model testing. Marcel van Gent 1 1 Deltares The new Delta Flume in Delft was constructed to facilitate large-scale physical model testing. The new Delta Flume has a length of about 300m, a width of 5m and a height of 9.5m. The maximum wave heights that can be generated are about Hs=2.2m with maximum individual wave heights in the range between Hmax=4m and 4.5m. This unique facility enables physical modelling at prototype-scale or at close-to-prototype scale. Preventing or diminishing scale-effects is especially important for coastal structures in which sand, clay, grass or other natural construction material is being applied. Besides projects with dikes and dunes, structures such as breakwaters, bed protections, monopiles, offshore wind farms, storm surge barriers are scheduled to be tested. Along with new facilities also new measurement techniques have been developed, both for the new Delta Flume and for the other wave facilities (e.g. wave basins). The new Delta Flume completes a set of wave facilities for physical model testing consisting of small and large-scale test facilities and 2D (wave flumes) and 3D (wave basins) facilities.

Wave attenuation over the Great Barrier Reef matrix Shari Gallop 1, Ian Young 2, Roshanka Ranasinghe 3, Tom Durrant 4, Ivan Haigh 5 1 University of Southampton 2 Australian National University 3 UNESCO-IHE, Deltares, Australian National University 4 Bureau of Meteorology 5 University of Southampton Offshore reef systems consist of individual reefs, with spaces in between, which together constitute the reef matrix. This is the first comprehensive, large-scale study, of the influence of an offshore reef system on wave climate and wave transmission. The focus was on the Great Barrier Reef, Australia, utilizing a 16 yr-record of wave height from seven satellite altimeters. Within the GBR matrix, the wave climate is not strongly dependent on reef matrix submergence. This suggests that after initial wave breaking at the seaward edge of the reef matrix, wave energy that penetrates the matrix has little depth-modulation. There is no clear evidence to suggest that as reef matrix porosity (ratio of spaces between individual reefs to reef area) decreases, wave attenuation increases. This is because individual reefs cast a wave shadow much larger than the reef itself; thus a matrix of isolated reefs is remarkably effective at attenuating wave energy. This weak dependence of transmitted wave energy on depth of reef submergence, and reef matrix porosity, is also evident in the lee of the Great Barrier Reef matrix. Here, wave conditions appear to be dependent largely on local wind speed, rather than wave conditions either seaward, or within the reef matrix. This is because the Great Barrier Reef matrix is a very effective wave absorber, irrespective of water depth and reef matrix porosity.

Pilot Application of Delft3D Flexible Mesh: Assisting a Field Campaign at the Sand Engine Arjen Luijendijk 1, Freek Scheel 2, Lisanne Braat 3, Niek Waagmeester 4 1 Deltares / TU Delft 2 Deltares 3 University Utrecht 4 Deltares For the execution of field measurements around the Sand Engine during MegaPEX2014 there was a need for operational model predictions. Local river outflow causes non-uniform velocities and spatially complex current patterns near the Sand Engine. For assessing the optimal timing and location of the instruments and GPS drifters, information on the predicted hydrodynamics was desired. A pilot application with the new Flexible Mesh version of Delft3D was therefore set up focusing on 3D hydrodynamic operational forecasts for the area covering the Rhine river mouth and Sand Engine. One single mesh was developed with flexible resolution in cell sizes in the areas of interest while covering all relevant (tide-influenced) areas, such as part of the river network, all port basins, Maasvlakte2 and large parts of the open sea. The number of grid cells did not exceed 100,000 while a resolution of tenths of meters was obtained around the Sand Engine and the river mouth area, which was virtually impossible to achieve using curvilinear grid methods. Comparisons of the model results with observed water levels, velocities and salinities showed very satisfying results. First comparisons with X-Band radar images show a remarkable good reproduction of the fresh water plume passing the Sand Engine. Besides the limited amount of grid cells, the flexible time step saved computational time as well.The present pilot application has clearly shown the benefits of the Flexible Mesh approach in saving grid cells and enclosing complex geometries with desired resolution in one single mesh, but more important it provides the ability to easily incorporate relevant large-scale phenomena in your simulation that at some moments can dominate the local hydrodynamics.

Sustainability of the multi-channel system in the Westerschelde under influence of dredging and disposal Zheng Bing Wang 1 1 Deltares & TUDelft The Westerschelde estuary is pre-eminently a system where sustainable coastal management is required. It serves as navigation channel to the Port of Antwerp, but it is also a Natura 2000 area. Its multi-channel system is an important natural characteristic. Deepening and maintenance of navigation channels are crucial human interferences. The disposal of dredged sediment can jeopardize the multi-channel system and thus the ecological value of the estuary. This paper presents an ongoing study meant to improve our knowledge on the morphological development of estuaries for supporting estuarine management considering accessibility for navigation and the ecological value. We focus on the question whether a multi-channel system in the Westerschelde can be sustained under pressure of future deepening and maintenance. Therefore, we explore the robustness of the system and try to quantify the threshold for which the system switches from a multi-channel system to a single-channel system. This is done by considering morphological development on different spatial scales, ranging from channel-shoal interaction to full estuary scale. Furthermore, the effects of sand transport and mud transport will be considered separately. The study is based on a combination of analyses of field data, theoretical analysis, process-based modelling with idealised schematisations and with complex geometries. The results of the study will directly be applied for developing better strategies for disposal dredged sediments, supporting decision making concerning sand mining and further deepening of navigation channels, and for monitoring the effects of human activities on the morphological development in the estuary.

Simulation of long-term morphodynamic behaviour of the Western Scheldt Gerard Dam 1, Mick van der Wegen 2, Dano Roelvink 3, Robert-Jan Labeur 4, Bram Bliek 5 1 UNESCO-IHE / Dam Engineering 2 Deltares 3 UNESCO-IHE Institute for Water Education 4 TU-Delft 5 Svasek Hydraulics In this paper we use a 2D process-based model to hindcast morphodynamic behavior of the Western Scheldt estuary. The periods of 1860-1970 (110 years) and 1905-1970 (65 years) are simulated. We compare the results to a historically unique dataset of bathymetric maps. The results show that the model results get better over time. The results show that the model is capable of simulating the large scale erosion and sedimentation that has occurred in the considered period. We attribute this to the self-organization of both the model and reality. The interaction between the major tidal forcing and the estuaries' fixed outline overrules other uncertainties over long time scales. Our research shows that process-based models applied in confined environments and under constant forcing conditions may perform well especially on long time scales. This makes them potentially suitable for centennial time scale forecasts related to, for example, climate change.

Modeling the morphodynamics of the mouth of the Scheldt estuary Jebbe van der Werf 1, Tomas van Oyen 2, Bart De Maerschalck 3, Arnold van Rooijen 4, Abdel Nnafie 5, Marcel Taal 6, Toon Verwaest 7, Lodewijk de Vet 8, Julia Vroom 9, Mick van der Wegen 10 1 Deltares 2 Flanders Hydraulics Research 3 Flanders Hydraulics Research 4 Deltares 5 Flanders Hydraulics Research 6 Deltares 7 Flanders Hydraulics Research 8 Deltares 9 Deltares 10 Deltares The Scheldt estuary is situated at the border of The Netherlands and Belgium. It consists of a river part from Gent to about Antwerpen, an inner estuary (Western Scheldt) from Antwerp to Vlissingen and a mouth or ebb-tidal delta. The average Scheldt river discharge is about 100 m3/s. The pre-dominantly semi-diurnal tide amplifies in upstream direction to a tidal range exceeding 5 m near Antwerpen, making the Scheldt a tide-dominated estuary. The Western Scheldt includes the entire gradient from fresh to salt water providing various habitats for marine flora and fauna. In addition to these ecological values, the estuary is of large economic importance as it provides navigation routes to the ports of Antwerp, Gent, Terneuzen and Vlissingen. Safety against flooding is the third important aspect of the Scheldt estuary. This paper presents the Delft3D-NeVla model to study the morphodynamics of the mouth, in relation to the other parts of the Scheldt estuary. We are particularly interested in the impact of possible morphological interventions in the mouth, such as the creation of a new navigation channel and the use of this dredged sediment to protect the coast. The 2DH model covers the entire Scheldt estuary and includes the effect of tide, wind, waves, dredging and dumping activities and the presence of non-erodible layers. The model will be validated against observation data of flow, waves, suspended sediment concentration and morphological change. In this way, sand transport and morphodynamics can be predicted on a time-scale of 10-20 years.

Land subsidence: the flooding threat in coastal cities, a case study in Ho Chi Minh city Duy Truong Tuan 1, Frits Dirks 2, Phi Ho Long 3, Ger de Lange 4, Ruben Dahm 5 1 HaskoningDHV Vietnam Ltd. 2 HaskoningDHV Nederland BV 3 Center of Water Management and Climate Change, Vietnam National University 4 Deltares 5 Deltares Many rapidly developing coastal cities, like Jakarta, Manila, Shanghai and Ho Chi Minh City, face flooding threats caused by a variety of reasons, some natural and some man-made. In many cases, land subsidence is posing a much bigger threat to the city than sea level rise. This phenomenon is not yet widely recognized and therefore attracts insufficient attention for remediation. The example of Ho Chi Minh City is elaborated where the effect of land subsidence is 3 to 10 times bigger than the effect of expected Sea Level Rise. Due to heavy rainfall, high river discharges and high tides, HCM City is experiencing frequent flooding of streets and wards, which is not life-threatening but causing nuisance and also significant economic damage. It is recognized that this situation is further aggravated by the impact of climate change, which is causing sea level rise and changes in rainfall distribution over the year. What is not widely recognized is the fact that land subsidence is occurring at an alarming rate and posing an even bigger threat to the city. The HCM City flood center, SCFC, has developed an Integrated Flood Management Strategy. In the preparation of that strategy, also an analysis is made of all uncertainties affecting the future flood risk, including sea level rise, land subsidence, precipitation, etc. To analyze the possible land subsidence, a model was developed, based on an existing groundwater model, to make land subsidence projections. Analysis shows that land subsidence is mostly caused by controlled and uncontrolled groundwater extraction for drinking and industrial water supply. Projections of future subsidence show very disturbing figures for Ho Chi Minh City, which are much larger than the expected sea level rise, even for the worst case (high emission) scenario. Based on this analysis, it is concluded that it is of great economic interest for HCMC to give high priority to activities aimed at 1) collecting more knowledge on land subsidence and 2) reducing the land subsidence as much as possible. Priority should be given to the reduction of groundwater usage in the vulnerable areas and developing a strategy towards renewable water resources. Other coastal cities in the region, like Jakarta, Manila, Shanghai and many others, face similar problems and can learn from the Ho Chi Minh City case to set up a strategy to cope with land subsidence.

Establishing a sediment budget in the ‘Kleine Noordwaard’ area of the Biesbosch inland delta Eveline van der Deijl 1, Eelco Verschelling 2, Marcel van der Perk 3, Hans Middelkoop 4 1 Universiteit Utrecht - Department of Physical Geography 2 Deltares 3 Universiteit Utrecht - Department of Physical Geography 4 Universiteit Utrecht - Department of Physical Geography Many deltas in the world cope with drowning and loss of delta land by sediment starvation and accelerated soil subsidence as a result of embankment of channels and drainage of land. The urgency of the problem is enhanced by sea level rise. Effective delta restoration requires a thorough understanding of the rates and mechanisms of delta aggradation and their controls. This study aims to quantify the rates and patterns of aggradation in the ‘Kleine Noordwaard’, a former polder area in the Biesbosch inland delta in the south-west of the Netherlands, in which water and sediment have been reintroduced since 2009. A sediment budget was established using existing bathymetric data collected using a multibeam echosounder and LiDAR digital elevation models collected since the opening of the polder, supplemented with field observations of the location and height of cut banks. Consecutive measurements of channel bathymetry showed a positive sediment budget in the channels between march 2009 and march 2013. During this period 59533 m3 of sediment was retained in the channels in the ‘Kleine Noordwaard’, which corresponds to an average sedimentation rate of 16.8 mm/year in the channels and 3.4mm/year over the entire area. Sedimentation and aggradation mainly took place in the channels in the central part of the former polder area, whereas the areas near the entrance and exit of the system were subject to channel erosion. It is therefore likely that a part of the sediment deposited in the central part of the system was supplied internally by upstream erosion of the channels. In addition, erosion of an island and old dikes also significantly contributes to internal sediment redistribution. Near-future research will focus on the sources of the sediment deposited in the area.

Delta Alliance - for the resilience of deltas worldwide Tom Bucx 1, Cees van de Guchte 2, Wim van Driel 3, Greet Vink 4, Renske Peters 5 1 Deltares 2 Deltares 3 Alterra, Wageningen University and Research Centre 4 UNESCO-IHE 5 Delta Alliance Delta Alliance is an international knowledge-driven network organization with the mission of improving the resilience of the world’s deltas. With increasing pressure from population growth, industrialization and a changing climate, it is more important than ever that these valuable and vulnerable locations increase their resilience to changing conditions. Delta Alliance brings stakeholders involved in delta management together in order to benefit from each other’s experience and expertise and as such contribute to an increased resilience of their delta region, building on scientific research and practical experiences. Delta Alliance has eleven network wings worldwide where activities are focused. The Delta Alliance has many linkages with other networks and initiatives such as the Global Water Partnership strategy 2014-2018, the Belmont Forum Deltas project, the GEF Transboundary Waters Assessment Programme, the Alliance for Global Water Adaptation, and the SIWI/UNEP initiated From Source to Sea partnership. This is further supported by the Sustainable Deltas Initiative 2015 as endorsed by ICSU. One of the most important research activities of the Delta Alliance in the past years was a comparative assessment of the vulnerability and resilience of 14 deltas wordwide, addressing various aspects of delta development and management of deltas. In this collaborative project of the Delta Alliance a framework for delta assessment is applied, combining a DPSIR approach with a Spatial Layer model and addressing also governance aspects. The advantage of this approach is that delta management and development is being considered in an integrated perspective and it is sufficiently generic which makes it applicable for all deltas. Comparison of the scorecards for the different deltas clearly shows that current overall sustainability is not satisfactory for most of them. Many are in the danger zone, which means that they are very vulnerable to adverse drivers of change. An inventory of research gaps has been carried out based on the delta descriptions. This provides an overview of the issues that have been identified for further research and potential opportunities for collaboration.

Dutch results of Pro-Tide a NWE-Interreg project on Developing, Testing and Promoting Tidal Energy in coastal and estuarine zone Leo van der Klip 1, Jacob van Berkel 2, Ivo Pothof 3 1 Province of Zeeland 2 Entry Technology 3 Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology / Deltares Pro-Tide's mission is to Develop, Test and Promote Tidal Energy in coastal and estuarine zone. Within the wide spectrum of Tidal Power applications, the Dutch project is specifically targeted at Low Head Tidal and River Hydropower, for conditions as found in the Brouwersdam project (typically 1 meter head, thousands of m3/s), and also in Delta rivers. In addition to the challenge how to join forces between Public and Private Partners, (PPP), the Dutch project specifically focuses on searching, finding and selecting the Best Available Technique, tests and demonstration this technology. The Best Available Technique is identified by a independent, purpose targeted and independent R&D-advisory board, using a Multi Criteria Analysis (MCA). The first step involves a worldwide technology scan, condensed in factsheets, covering 10 categories and providing a comprehensive overview of available techniques. The subsequent MCA utilizes selection criteria, ranging from Levelized Costs of Energy (LCoE) and Fish Friendliness both with 0.3 weighting factor to Export Ability with 0.05 weighting factor. The best techniques identified in the MCA are now being tested for performance and fish friendliness. The first test results which are very relevant for future application will be presented, also in conjunction with economic parameters. In the presentation, the process of identifying an selection the Best Available Technique will be outlined. The overview and ranking of techniques will be presented, with considerations why a technique is in more or less extend suitable for application in Ultra Low Head Tidal- and River Power systems. Overall, the paper and presentation will provide a clear overview and targeted- and quantitatively tested selection of Ultra Low Head Tidal and Delta River Power techniques.

Determining accurate weir discharge-water level relationships via CFD Aldo Tralli 1, Tommaso Boschetti 2, Francois Clemens 3 1 deltares 2 Department of Civil, Chemical and Environmental Engineering University of Genova 3 Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology / Deltares This study documents the use of Computational Fluid Dynamics (CFD) to obtain accurate Q(h)-relations on two weir structures in the storm protection system in the municipality of Eindhoven , in the Netherlands. Being able to accurately determine weir discharges is of key importance in urban water management: the most common method is performing a level measurement and calculating the discharge using the standard weir equation. Since this equation is only valid in certain conditions, this can lead to large deviations from the actual discharge in a real-life situation: calibrated parameters, relevant for a specific weir, would be needed, but are rarely determined because of costs and practical reasons. As a consequence, large uncertainties exist in the determination of the flow near weirs, despite the availability of measurements. CFD has been proven to correctly reproduce the water flow over a weir ([1], [2]): accurate Q(h)-relationships can be derived from the CFD calculations, providing a much better description of the actual weir discharge, than the standard equation. The CFD methodology validated in [2] against experimental data, is further documented here and applied to two different non-standard weirs: the Q(h)-relations obtained via CFD are compared with the standard equations and the discrepancies are quantified. The end goal is to implement this enhanced information to the wastewater control system of the municipality. Bibliography: 1. S. Isel , M. Dufresne , J.B. Bardiaux , M. Fischer & J. Vazquez , Urban Water Journal (2013): Computational fluid dynamics based assessment of discharge-water depth relationships for combined sewer overflows, Urban Water Journal, DOI: 10.1080/1573062X.2013.806561 2. P.van Daal-Rombouts, A.Tralli, F. Verhaart, J. Langeveld, F. Clemens, 13th IAHR/IWA International Conference on Urban Drainage(2014) : Determining accurate weir discharge-water level relationships.

Predicting flooding events on gravel coasts Robert McCall 1, Gerd Masselink 2, Timothy Poate 3, Dano Roelvink 4 1 Deltares 2 Plymouth University 3 Plymouth University 4 UNESCO-IHE Institute for Water Education Gravel beaches and barriers occur on many high-latitude, wave-dominated coasts across the world. Due to their natural ability to dissipate large amounts of wave energy, gravel coasts are widely regarded as an effective and sustainable form of coastal defense. However, despite their usefulness as a form of coastal defense, relatively little research has been directed towards understanding the response of gravel beaches to storms, leading to a lack of understanding of the physical processes on gravel beaches. At present, coastal managers have very limited guidance in choosing coastal management strategies to prevent flooding during storms. In this paper we address this issue by investigating typical flood defence strategies at two natural gravel beaches in the UK using a newly-developed a process-based morphodynamic model called XBeach-G, which has previously been shown to have good skill in simulating hydrodynamics and morphodynamics on gravel beaches during storms. Application of the process-based model warns of an overestimation of coastal flooding resilience in swell-dominated conditions along the southern UK coastline and highlights current beach reprofiling schemes as unsustainable, in particular with respect to extreme storm events.

RISC-KIT: Resilience-Increasing Strategies for Coasts – toolkit Ap van Dongeren 1 1 Deltares INVITED Recent and historic high-impact events have demonstrated the flood risks faced by exposed coastal areas. These risks will increase due to climate change and economic development. This requires a re-evaluation of coastal disaster risk reduction DRR strategies and prevention, mitigation and preparedness PMP measures. To this end, the UN Office for Disaster Risk Reduction formulated the Hyogo Framework for Action, and the EU has issued the Floods Directive. By their nature, neither is specific about the methods to be used to assess coastal risks, particularly those risks resulting from dune and structure overtopping, the non-stationarity of surge and flash flood events, and coastal morphodynamic response. This paper describes a set of open-source and open-access methods, tools and management approaches to fill this gap. A Coastal Risk Assessment Framework will assess coastal risk at a regional scale. Thus critical hotspots can be identified for which an impact-oriented Early Warning System/Decision Support System is developed. This can be applied in dual mode: as a forecast and warning system and as an ex-ante planning tool to evaluate the vulnerability. The tools are demonstrated on case study sites on a range of EU coasts with diverse geomorphic settings, land use, forcing, hazard types and socio-economic, cultural and environmental characteristics. Specific DRR plans will be developed for all sites. A management guide of PMP measures and management approaches is to be developed. The toolkit will benefit forecasting and civil protection agencies, coastal managers, local government, community members, NGOs, the general public and scientists.

Towards a nonlinear meander evolution model Shiyan Zhang 1, Dong Chen 2, Koen Blanckaert 3, Willem Ottevanger 4, LeiLei Gu 5 1 Chinese Academy of Sciences 2 Chinese Academy of Sciences 3 LCH - ENAC - EPFL 4 Deltares 5 Chinese Academy of Sciences The evolution of meanders has been the focus of research challenging river engineers for decades. The study simulates the natural evolution of meandering processes by coupling a nonlinear flow model (by Blanckaert and de Vriend, 2010) with the Bank Erosion and Retreat Model (BERM, by Chen and Duan, 2012). Distinguished from our linear meander evolution model (Chen and Duan, 2006) which adopted the first-order analytical solution of flow field in a sine-generated channel (by Johannesson and Parker, 1989), the present model is applicable to any channel planforms without curvature restrictions therefore more suitable for moderately and strongly curved channels. The computed results demonstrate the improvement of simulation of meander evolution by adopting the advanced hydrodynamic model.

Land subsidence, sea level rise and urban flooding: coping strategies in coastal cities Ger de Lange 1, Tom Bucx 2, Roelof Stuurman 3, Gilles Erkens 4 1 Deltares 2 Deltares 3 Deltares 4 Deltares Land subsidence increases the threat of urban flooding. This is evident by the increasing instances of coastal flooding in rapidly developing coastal cities, but also the increased runoff from climatic and topographic changes finds its way into subsiding cities. An assessment framework was developed that analyses the situation of a city with respect to awareness, knowledge, data availability, governance and coping strategy concerning land subsidence and flood prevention. We show that cities have seldom reached the stage where a coping strategy is developed, let alone that a governance structure is in place to implement it. This is illustrated by looking at cases, such as Tokyo, Ho Chi Minh City, New Orleans, Jakarta, Dhaka and Rotterdam, where investments in flood risk mitigation run into hundreds of millions of dollars/euros. We show that the timescale of the process leading from awareness to the implementation of coping strategies as compared to the timescale of the development of the flooding threat leads to the conclusion that immediate action is necessary if only to render these investments durable in the long term. We give some examples of the transition from mitigation to adaptation of land subsidence effects.

Development of coastal-FEWS: early warning system tool development Simone De Kleermaeker 1, Wiebke Jager 2, Ap van Dongeren 3 1 Deltares 2 Delft University of Technology 3 Deltares Coastal zone risks are likely to increase due to a combination of increased coastal hazards (inundation, wave attack, coastal erosion) due to climate change and an increase in economic development in the coastal zone. Thus, there is a need to protect coastal infrastructure and population through regional and national disaster risk reduction strategies. An essential ingredient in these strategies is forecasting, early-warning and decision support systems (EWS/DDS), which are typically applied to critical coastal areas. The challenges for developing a modern EWS are found in the integration of large data sets, specialized modules to process the data, and open interfaces to allow easy integration of existing modeling capacities. In response to these challenges, Delft-FEWS provides a state of the art EWS framework, which is highly customizable to the specific requirements of an individual organization. For coastal applications, the EWS component is a 2D model train of hydro-meteo and morphological models which computes hazard intensities. From the hazard intensity for every hazard type and the attributes (density, sensitivity and value) of every receptor type, the total expected impact can be obtained using the DSS. In the EU-funded project RISC-KIT, the robustness and applicability of the coastal EWS/DSS tool will be demonstrated on case study sites on the coasts of all EU regional seas with diverse geomorphic settings (open coasts, lagoons, salt marshes, deltas and estuaries), forcing (tides, surges, waves) and hazard types (erosion, overtopping, coastal rain-driven flash floods). For these areas, EWS are developed to provide real-time (short-term) forecasts and early warnings based on generic tools so that a common functionality across Europe can be achieved. An important innovation of the EWS/DSS lies in its application in dual mode: as a forecast and warning system and as a consistent ex-ante planning tool to evaluate the long-term vulnerability due to multiple (low-frequency) coastal hazards, under various climate-related scenarios.

Operational wave forecasts in the southern north sea Caroline Gautier 1, Sofia Caires 2 1 Deltares 2 Deltares Wave forecasts are paramount for the safety of coastal regions. Not only high water levels but also waves can pose a thread for flood defenses. Proper wave forecasts are thus essential in flood forecasting. Furthermore, larger ports need wave forecasts to optimize their tidal window. Also for predicting workability offshore, wave forecasts are needed. After a year of pre-operational use, from 2015 on the SWAN-North Sea model will be the operational wave forecast model of the Dutch part of the North Sea. It consists of two grids. The first coarse grid covers a large area (-12º to +9º E; 48º to 64ºN) and computes boundary conditions for the detailed nested model domain. The SWAN-North Sea simulations run continuously within FEWS-North Sea. Four times a day, a run is started, with a forecast horizon of 48 hours. SWAN-North Sea makes use of wind fields from the Dutch meteorological Institute (KNMI), wave boundary spectra from the operational wave model of the European Centre for Medium-Range Forecast (ECMWF) and water level and current fields from the operational hydrodynamic models WAQUA-DCSM and WAQUA-ZUNO. Sensitivity tests indicated that the model performs best with the whitecapping formulation according to Komen et al. (1984, J. Phys. Oceanogr.). Based on a six month validation at twelve locations, the models relative bias is 4% for significant wave height Hm0 and -30% for low frequency wave height HE10. The scatter indices are respectively 18% and 47%. The low frequency wave height HE10, defined as the significant wave height based on the domain 0.03 Hz - 0.10 Hz, turns out to be a hard parameter to simulate. Because of the steep low frequency flank of the wave spectrum, a small deviation in spectral shape has large effect on the forecast quality of this parameter. However, it is an important parameter determining to a large extend the motion of large vessels. Given the less good performance of the model for this parameter the best way to correct the model forecast spectra and hence the HE10 using observations, is being investigated.

Towards time and space evolving extreme wind fields Joana van Nieuwkoop 1, Sofia Caires 2, Jacco Groeneweg 3 1 Deltares 2 Deltares 3 Deltares Time and space evolving extreme wind fields are needed to produce accurate and realistic extreme hydraulic loads. To fulfill this need, a semi-parametric method based on the theory of max-stable processes has been proposed that can be used to determine the time and space evolving wind fields associated with a given return value of wind speed at a specified reference location. The method uses wind velocity time series over a grid of locations and their location-specific extreme value distributions in order to ‘lift’ observed extreme events (storms) into yet unobserved and even more extreme events. Because the lifted fields are needed to force hydrodynamic models, they need to be continuous in time and space and to extend over a few days before the peak of the storm in order to allow the spin up of the hydrodynamic models. Thus, even if the original values of the wind fields are not above the threshold used to determine the location-specific extreme value distributions at a given location and instant, they still need to be lifted. This is achieved by augmenting the location-specific extreme value distributions by the empirical distributions of the observations and lifting also the values below the thresholds. Mainly as a consequence of this procedure, the resulting lifted wind fields have low temporal and spatial wind speed gradients away from the peak of the storm. These gradients have raised concerns about the validity of the fields and it has been suggested that the lifting by means of a simple scaling factor may be preferable. To address these concerns, a thorough validation of the lifted fields has been carried out assessing the ability of the lifted fields to reproduce extreme hydraulic conditions. The main recommendation of this study is that a lifting method defined as the combination of the method based on the theory of max-stable processes and a fixed factor method be considered further for the determination of temporally and spatially varying hydraulic loads.

Validation of SWAN under extreme conditions in the Wadden Sea Amaury Camarena 1, Caroline Gautier 2, Joana van Nieuwkoop 3 1 Deltares 2 Deltares 3 Deltares This paper assesses the influence of different physical settings used to calibrate the spectral wave model: SWAN (Simulating WAves Nearshore). Even though the accuracy of SWAN has been assessed in various studies before, the applicability of SWAN to simulate extreme events has not been thoroughly evaluated. On 5th and 6th of December of 2013 a severe storm was successfully measured at a number of locations in the Wadden Sea, providing a rich dataset to compare SWAN results with measured data. Stationary simulations with different settings are carried out, focusing on the tidal inlet of Ameland and the eastern part of the Wadden Sea. It was found that the choice of whitecapping formulation and associated calibration parameters strongly influences the results of the SWAN model. Overall it is concluded that SWAN can accurately simulate waves during extreme events when the adequate combination of settings are used.

Global-scale modelling of sea level extremes to estimate coastal flood risk Sanne Muis 1, Martin Verlaan 2, Hessel Winsemius 3, Philip Ward 4, Jeroen Aerts 5 1 IVM VU University 2 Deltares 3 Deltares 4 IVM VU University 5 IVM VU University Increased coastal flood losses are likely to be one of the most costly impacts of climate change. Despite this, there are only a few studies on global coastal flood risk. These studies are all based on the DIVA database, which contains the only globally available data on extreme water levels. However, the water levels included in this database are based on simple assumptions and contain information for only four return periods. Moreover, the validation of these water levels is poorly documented. Hence, before we can accurately assess the impact of changing climate on global coastal flood losses to prioritise global adaptation actions, there is a need for an improved estimation of coastal water level extremes on a global-scale. On a regional scale, hydrodynamic models with meteorological forcing are frequently applied to calculate high water levels resulting from storm surges. However, as the modelling of surges in shallow coastal areas requires a high-resolution model grid, this approach is computationally too costly for most global models. The recent application of unstructured grids (or flexible mesh) in hydrodynamic models, allowing local refinement of the grid, has enabled the development of a global tide and surge model with a sufficient resolution in coastal areas, while maintaining computational efficiency. The global model is developed using Delft3D Flexible Mesh software from Deltares. By forcing the model with wind speed and atmospheric pressure derived from the ERA-Interim global reanalysis we can generate a 34 year hindcast of coastal water levels. Subsequently, extreme value distributions are fitted to the annual maxima to estimate exceedance probabilities for each output location. Here, we present first insights in the performance of the model by a comparison of the simulated water levels with tide gauge observations and the levels in the DIVA database.

Modelling River Dunes in the Rhine Branches Under Extreme Floods Satomi Yamaguchi 1, Sanjay Giri 2, Mohamed Nabi 3, Jonathan Nelson 4, Yasuyuki Shimizu 5 1 Civil Engineering Research Institute of Hokkaido 2 Deltares 3 Deltares 4 USGS- Geomorphology and Sediment Transport Laboratory 5 Hokkaido University The Waal branch of Rhine system is considered to be an important fairway. The flood events and extensive navigation cause significant morphological changes, which create difficulties for safe and efficient navigation particularly during low water period. Therefore, it is important to predict the bed level changes, particularly evolution of bed forms during the flood event including both the high water and low water periods. Besides this, it is also important to understand the bed form evolution process and resulting flow resistance during extreme floods in order to quantify their effect on water levels. Many attempts have been made to improve both understanding and predictive capability of bed form evolution, transition and associated resistance under varying flow conditions. The interaction among the flow-field, bed forms and sediment transport is quite complex and difficult to capture in simple models. Giri and Shimizu (2006) and Giri et al. (2014) made some noticeable efforts to numerically replicate the dune formation and evolution processes. They proposed a morphodynamic model that successfully reproduces fluid and bed form dynamics in a coupled manner under arbitrary steady or unsteady flow condition. In this study, we have addressed the issue associated with bed form evolution process during floods including some test cases under extreme condition in the Rhine branches, particularly in the river Waal. At first, we analyzed the observed data during moderate floods in the Waal. The bed level data were measured during two different flood events in 1997 and 1998 respectively. A vertical two-dimensional morphodynamic model with a free-surface flow condition, which includes equilibrium, non-equilibrium bed load transport as well as suspended sediment transport modules, was used to replicate the bed form evolution processes under the condition of varying flows. The boundary condition for vertical two-dimensional model was extracted from calibrated hydrodynamic models (WAQUA and Delft3D). A preliminary result shows that bed forms are present even during extreme (design) condition. This study reveals the capability of a numerical model, which can be applied to predict real-world river dunes and drag evolution with hysteresis effects in physics based manner.

Estuarine Mangrove Squeeze In The Mekong Delta Son Truong 1, Qinghua Ye 2, Marcel Stive 3 1 Section of Hydraulic Engineering,Faculty of Civil Engineering and Geosciences, Delft University of Technology, P.O.Box 5048, 2600GA, Delft, The Netherland 2 Deltares 3 TU Delft In the Mekong Delta Estuaries (MDES), due to the continuously increasing extension of local agriculture and fish farming in many regions, mangroves have degraded into a very narrow strip of sometimes less than 50 m in width. River banks at those locations are often suffering from erosion and are unstable. Many efforts have been undertaken to protect the river banks as well as to maintain the mangrove forests, but until now very limited results have been achieved. The erosion trend is anticipated to continuously increase in the near future. The threat to the existence of the coastal mangroves or tidal wetland habitats caused by the compound impacts of the human-induced and sea-level rise induced is increasingly recognized as term “squeeze”. While the “squeeze” issue for coasts has been increasingly recognized, the similarity for mangroves in estuary area is less well acknowledged. The difference is that while the main hydrodynamic forces effect on mangroves at coastal area are waves, mangroves in estuaries mainly affected by the flow, i.e. flow from tidal action and flow from river discharge. This implies a similarity with the hydrodynamics of floodplain vegetated channels. By analyzing the data from literature and from satellite images together with the application of the rigid 3D Vegetation in Delft3D-FLOW, the impacts of local fish-farming construction on the hydrodynamic of riverine mangrove forest in MDES is being studied. Results reveal a critical width required for the stable development of the riverine mangrove forest in MDES. Besides, flow penetration from the main channel into the mangrove regions play an important role and cannot be neglected in understanding the behaviors of riverine mangrove towards changes in landward boundary conditions.

Batumi coastal protection: facing decreasing river discharges of gravel and canyons traps Maria Di Leo 1 1 Technital SpA The beaches of Batumi coast are formed by gravel sediment carried by the Chorokhi River. Two submarine canyons stretch from the far depths to Batumi coast: one reaches Batumi Cape in the north, the other one lies directly opposite the mouth of river Chorokhi in the south. Previous studies have shown that part of the pebbles from the river flow into this canyon, hence failing to feed the beaches downdrift. Furthermore human interventions on the river (sediment mining, water flow regulation) have reduced in time the amount of sediment available to the beach, and further reduction is expected due to planned construction of new dams along the river. As a result the beach is suffering erosion in the southern stretch. In addition, geotechnical instability processes have been identified involving the canyon in the Northern area of Batumi coast. Here two different instabilities coexist: the main instability process, which led to a massive landslide observed in 1999, and a secondary instability process, which is independent from to the main one and involves smaller soil volumes. Both these processes can be related to the high sedimentation rate in the area. From a geotechnical point of view, especially with reference to the main landslide, the reduction in the sedimentation rate or better its halt could prevent any further instability phenomenon. The design process, developed with support of Deltares, has gone through different steps. At first, dominant natural mechanisms governing the transport of beach material and acting upon the coast of Batumi have been identified and quantified. Secondly, different design options have been evaluated considering the development of different coastal functions, both based on a technical and cost-benefit analysis. State-of-the-art numerical models have been used extensively in the study of the reference situation and in the evaluation of the different options.

Transferability and parameter uncertainty of hydrological models for estimating future mean and extreme discharges in the context of climate change Lu Wang 1, Shreedhar Maskey 2, Roshanka Ranasinghe 3, Han Vrijling 4, Pieter van Gelder 5 1 Delft University of Technology 2 UNESCO-IHE Institute for Water Education 3 UNESCO-IHE, Deltares, Australian National University 4 Delft University of Technology 5 Delft University of Technology Previous studies on climate change impacts have paid considerable attention on assessing the uncertainties associated with greenhouse gas emission scenarios and General Circulation Model (GCM) structures. Increasing studies stress the need for routinely testing the performance and analysing uncertainty of hydrological models in the impact assessment. The overarching objectives of this study are 1) to investigate the transferability of the hydrological model parameters to climatic conditions that are different from that in the calibration period, and 2) to compare the uncertainties in the future mean and extreme river discharges due to the equifinality of model parameters and the choice of calibration periods. A lumped Xin’anjiang Hydrological Model of the Huai River Basin in China is used to test the methodology. The transferability of model parameters is tested in the context of historical climate variability using the differential split-sample test. Four GCMs participating in the CMIP5 data portal are selected. The results show that the transferability of the parameters calibrated from a wet period to a dry period is poorer than the other way around. The model error as well as the variability in the simulation due to equifinality increase with the increase in the difference in rainfall amounts between the calibration and validation periods. Generally, the uncertainty due to the choice of calibration periods takes larger share of the total parameter uncertainty in the projected future mean discharge. When the calibration period contains enough information of climate variability, the equifinality becomes the main source of parameter uncertainty for high-return-period extreme discharge. The results will provide the basis for better understanding the uncertainties in assessing hydrological impacts of climate change.

Sustainable ports development concept as adaptive, environmental and socio-economic growth Cor Schipper 1 1 Deltares The concept of sustainable port infrastructure is central to sustainable green growth strategies developed, because decisions made within such a framework are long-lasting, more adaptive and resilient to change, environmental friendly, and more cost effective. In the design of ‘Green Ports’ it helps to mitigate sea level rise and increased storminess caused by climate change. Increasing demand on space in delta areas, combined with external threats such as climate change, accelerated sea level rise and subsidence, requires multi-functional approaches in water management. This requires a new way of managing, and specific knowledge and expertise in the field of eco-engineering. The way in which ports are managed has changed over the years when environmental criteria became an intrinsic part of operations and growth. We discuss some dedicated projects for specific port development and related projects and application of sustainable ports. To identify the Green Port concept a study of knowledge is made of operations in the world wide ports. We present the multi-disciplinary approach and a record of accomplishments in this field

Modeling of wave attenuation by vegetation with XBeach Arnold van Rooijen 1, Jaap van Thiel de Vries 2, Robert McCall 3, Ap van Dongeren 4, Dano Roelvink 5, Ad Reniers 6 1 Deltares 2 Boskalis 3 Deltares 4 Deltares 5 UNESCO-IHE Institute for Water Education 6 Delft University of Technology Over the past decades the effect of vegetation (e.g. kelp, mangroves, sea grass) on nearshore coastal processes has received more and more attention. In recent years several numerical wave models have been extended to include this effect. In the current study, the numerical storm impact model XBeach is extended with formulations for damping of short waves, infragravity waves, and mean flow. The model is verified using a number of laboratory test cases. XBeach is found to be able to reproduce the damping effect of vegetation on waves well, even though the amount of calibration done was limited. This work is considered as a first step only, and further model developments regarding vegetation implementation in XBeach are foreseen for the near future. Eventually, XBeach should be able to accurately take into account the effect of relatively complex vegetation species (e.g. mangroves) on the nearshore hydro- and morphodynamics in a computationally efficient way.

FIeld measurements - do they provide the ground truth? Ivo Wenneker 1, Niels Jacobsen 2 1 Deltares 2 Deltares Field measurements at sea of water levels and waves yield data for practical and research purposes. For example, they feed operational numerical models for ship navigation and storm surge prediction, and can be used for model validation. In such and other applications, field measurements are assumed to provide the ‘ground truth’. One expects that ‘redundant measurements’, i.e. measurements of some quantity at the same location by more than one instrument, would lead to (almost) identical data. We studied several years of ‘redundant data’ of: • water levels, measured at sea poles located offshore, near the coast, and sheltered in an estuary (instruments: Digital Level Meter (DLM), Radar and Step Gauge); • waves, measured at sea poles located in the surf zone (instruments: Step Gauge, Pressure Sensor, S4, Cap Wire). By comparing data of one instrument with that of another, we concluded that: • for ‘mild’ conditions, data differences are often minor; but • for ‘extreme’ conditions (e.g., storms, breaking waves, large tidal currents), data differences between instruments go up till 20 cm (water level), 50 cm (wave height) and 0.5 s (wave period). This implies that one should be cautious to classify field data obtained in ‘extreme conditions’ as ‘ground truth’. This is unfortunate, also because in such conditions numerical models are often less reliable. We will present various causes that can lead to these differences.

Wave growth at short fetches Jamie Morris 1, Caroline Gautier 2, Gerbrant van Vledder 3 1 Deltares 2 Deltares 3 Van Vledder Consulting For short-fetch areas (typically 500-5000m), such as lakes and wide rivers, the performance of SWAN is poorer than for longer fetches. Deltares (2013) showed an under prediction of wave height (order of 15%) for short fetches at Lake IJssel (Netherlands). This inconsistency in growth behavior suggests a shortcoming in the parameterizations of the physical processes responsible for wave evolution. To increase the reliability of SWAN model results, we investigated the parameters controlling wave growth at short fetches. Wind and wave data was collected at Lake IJssel where near ideal fetch-limited conditions can be observed during offshore winds. Observations along a cross-shore transect at three locations (FL49, FL48, and FL47) with fetches of 800 m, 1600 m and 10 000 m were analyzed. Observations of wave height were compared to a number of empirical growth curves (e.g. Kahma and Calkoen (1992)). Results indicate that for similar dimensionless fetches (gF/U10^2), the wave observations show a great deal of variability in dimensionless wave height (gHm0/U10^2). This can be partially attributed to measurement error, and due to simplification of the wind speed to one moment in time. However, it can also imply that parameters other than the typically used wind speed and fetch must be used to scale wave growth when the fetch is limited. Furthermore, the observations (at FL48 and FL49) generally lie above the theoretical growth curves. As SWAN is calibrated using the theoretical growth curve of Kahma and Calkoen (1992), this explains the under-prediction in the SWAN results. The role of a number of parameters in influencing wave growth was investigated (inverse wave age, wave steepness, temporal wind speed gradients, gustiness, and atmospheric stability). It has been determined that wind gustiness and wave steepness can explain some of the scatter in the wave observations, where steeper waves, and gustier winds result in higher wave heights than the contrary. Deltares, 2013b: SWAN uncertainties for short fetches, dd Dec, 2013. Report 1207807-001-HYE-0008. Kahma, K.K., and C.J. Calkoen, 1992: Reconciling discrepancies in the observed growth of wind-generated waves. J. Phys. Oceanogr., 22, 138901405.

Predicting wave-induced loads on a moored ship with a non-hydrostatic wave-flow model Dirk Rijnsdorp 1, Marcel Zijlema 2, Julie Pietrzak 3 1 TU Delft 2 TU Delft 3 Delft University of Technology Traditionally, ships are moored at jetties located inside a sheltered area (such as a harbour), which reduces wave impacts and allows for safe operations. With the recent increase of ship dimensions, entrance channels are deepened and widened, and jetties are located closer to the harbour entrance. Besides, there is an increasing demand for the construction of marine jetties at exposed locations, especially for the Liquefied Natural Gas industry. These developments lead to a greater exposure of moored ships, and puts stringent demands on the design of the jetties and mooring systems. This makes an accurate prediction of the wave-induced response of a ship, moored in a harbour or coastal region, of vital importance to ensure safe operations (e.g. loading and offloading activities). Several studies have used a model train to predict the wave-induced loads and motions of a moored ship (e.g., Bingham 2000, van der Molen and Wenneker, 2008, Dobrochinski 2014). Such a model train combines a wave-resolving model, which accounts for the wave propagation inside the domain (excluding the presence of a ship), with a diffraction model that computes the wave-induced forces on the ship. The overall aim of this study is to develop a single numerical model tool, to predict the wave-induced response of ship that is moored in a harbour or coastal region. For this purpose, the open-source non-hydrostatic wave-flow model SWASH (Simulating WAves till SHore, Zijlema et al., 2011) will be extended by nesting a floating body. In this work, we will present the numerical framework and validate the proposed method. The capabilities of the model will be assessed for the prediction of wave-induced loads on a restrained ship, that is located in open water and in a harbour basin. Model predictions will be compared with results of a physical model experiment (WL|Delft Hydraulics report, 2004), that was conducted in the Vinjé basin at Delft Hydraulics (now Deltares). References Bingham, H.B. (2000), Coastal Engineering 40, 21–38. Dobrochinski, J.P.H. (2014), M. S. thesis, Delft University of Technology, Delft, Netherlands. van der Molen, W., Wenneker, I. (2008), Coastal Engineering 55, 409-422. WL|Delft Hydraulics report, (2004), Delft, The Netherlands. Zijlema M., Stelling G.S., Smit P.B., (2011), Coastal Engineering, 58, 992-1012.

Coupling a near field outfall model with a far field hydrodynamic model Philip Roberts 1, Beatriz Villegas 2, Robin Morelissen 3 1 Georgia Institue of Technology 2 Consultant 3 Deltares The fate of outfall discharges in coastal waters involves hydrodynamic phenomena that act over wide ranges of temporal and spatial scales. Near field mixing occurs within a few minutes and a few tens of meters after which the plume is either trapped by density stratification or reaches the water surface. It then drifts with the current and is diffused by oceanic turbulence in the far field by processes that occur on time scales of hours to days and length scales of hundreds of meters to kilometers. It is not feasible to encompass all these scales in one model, so separate models are needed for the near and far fields that must be coupled. Near field mixing depends on the wastewater flow rate, current speed and direction, and density stratification. These can vary rapidly, resulting in wide variations of plume rise height and dilution; they can be simulated by the model NRFIELD. Far field transport depends on large-scale circulation patterns driven by winds, tides, and local freshwater sources; these processes can be simulated by the hydrodynamic model Delft3D. In this paper we describe the coupling of NRFIELD and Delft3D to produce a state-of-the-art system for predicting the impacts of wastewater discharges in coastal waters. Three steps are involved. First, Delft3D-FLOW is run to generate time series of currents and density stratifications near the diffuser. These time series are then used as inputs to NRFIELD, producing a time series of plume behavior, especially its rise height, thickness, and dilution. This time series in turn becomes an input to the transport modules of Delft3D. Mass sources of, for example bacteria, are apportioned into the grid cells that overlap the plume with initial concentrations and volumes computed from the near field dilution. The far field advective transport is then predicted by a model that uses the currents from the FLOW module, and either the gradient-diffusion type water quality model WAQ, or the particle-tracking model PART. For bacteria, the particle tracking module is best as it does not suffer from high numerical diffusion that can considerably overestimate impacts at specific locations and decay models of bacterial mortality can be readily incorporated. In this paper we describe the procedure for coupling NRFIELD and Delft3D and give an example application to San Francisco, California.

Transition structures in grass slopes of primary flood defences tested with the wave impact generator Paul van Steeg 1, Astrid Labrujere 2, Roy Mom 3 1 Deltares 2 Ministry of Infrastructure and Environment, Rijkswaterstaat 3 Infram BV The stability of grass slopes on primary flood defences under wave attack is an important aspect with respect to the strength of the entire dike. Therefore there is a need to understand the behaviour of grass slopes under hydraulic loads. Since grass cannot be scaled properly, research is usually conducted in full-scale wave flumes or, more recently, with use of several hydraulic simulators such as the wave impact generator. The wave impact generator is a special designed machine which simulates a sequence of wave impacts by releasing amounts of water on a grass slope. The hydraulic load is comparable with the load due to an irregular wave field with a significant wave height of Hs _ 0.6 m – 0.7 m and a wave steepness of sop _ 0.05 which represents riverine wave conditions. The development of the wave impact generator is described in Van Steeg et al (2014a). Within the project WTI 2017 (“Research and development of safety assessment tools of Dutch flood defences”) the wave impact generator was applied on several existing dikes. Variations on the dikes were different grass and clay quality (described in Van Steeg et al, 2014b), but also several transitions and objects. The present paper will describe and analyse tests that were performed on transition structures and objects in the grass slope. It was concluded that for several tests the stability of the grass slope was significantly lower when a transition or object was applied. This implies that transition structures are in some cases normative for the strength of grass slopes. References Van Steeg, P., Klein Breteler, M. and Labrujere, A., 2014a, Design of wave impact generator to test stability of grass slopes under wave attack, (in press), 5th Conf. on the Application of Physical Modelling to Port and Coastal Protection, Coastlab, 29 Sept. – 2 Oct. 2014, Varna, Bulgaria. Van Steeg, P., Klein Breteler, M. and Labrujere, A., 2014b, Use of wave impact generator and wave flume to determine strength of outer slopes of grass dikes under wave loads, (in press), 34th Int. Conf. on Coastal Engineering, 15-20 June 2014, Seoul, Korea

A European flood risk model and its use for analyzing climate change adaptation strategies Andreas Burzel 1, Friederike Holz 2, Hessel C. Winsemius 3, Karin de Bruijn 4, Laurens M. Bouwer 5 1 Deltares 2 University Kiel 3 Deltares 4 Deltares 5 Deltares With respect to climate change, there is an increasing attention in scientific and policy making communities of weather-related disaster risks. Moreover, there is increasing need to assess costs and benefits of climate adaptation at scales beyond river basins, in order to set priorities for action and financing in the context of the EU Adaptation Strategy at the European scale. The goal of this research as part of the FP7 BASE project is to develop a riverine flood risk model that can be applied at Pan-European scale and that is able to project changes in flood risk due to climate change and socio-economic developments in the future. For this purpose, the global flood hazard estimation method developed by Winsemius et al. (2013), that produces return period flood inundation datasets at 30 arc second resolution, for present day (EU WATCH) and future climate forcing (IPCC scenarios RCP4.5 and 8.5). These datasets are used for the land-used based assessment of flood impacts. In addition, the current standard of flood protection as firstly applied in Jongman et al. (2014) is considered in this European flood risk model. Compared to previous studies, the high resolution of both hazard and exposure input data as well as the use of the CLC 2006 dataset and the consideration of GDP up to the NUTS3 level allow for a detailed assessment of current and future flood risks. The results show the expected changes in flood risk in the future. For example, on a NUTS2 level, flood risk increases in some regions up to 179% (between the baseline scenario 1960-1999 and time slice 2049). On country level flood risk increases up to 60% for selected climate models. Further results of this flood risk analysis on a European scale will be shown at the conference. The results will be critically discussed under the aspect of major uncertainties in both future flood hazards as well as in the applied depth-damage functions. As part of the current research, the results from this study are compared with flood risk assessments on either local or regional scales. The findings from this analysis will be also presented at the conference.

On the set-up of field research in sumps of wastewater pumping stations Alex Duinmeijer 1, Francois Clemens 2, Ivo Pothof 3, Femke Verhaart 4 1 Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology / Municipality of Rotterdam 2 Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology / Deltares 3 Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology / Deltares 4 Deltares On the set-up of field research in sumps of wastewater pumping stations Alex Duinmeijer (a,b), Ivo Pothof (a,c), Francois Clemens (a,c) & Femke Verhaart (c) (a) Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology, PO Box 5048, 2600 GA, Delft, The Netherlands E-mail (Corresponding author) (e) Engineering Agency Municipality of Rotterdam, PO Box 6633, 3072 AB, Rotterdam, The Netherlands (c) Deltares, PO Box 177, 2600 MH, Delft, The Netherlands Abstract A large number of sumps of wastewater pumping stations experiences problems due to the presence of sewer sludge, floating fat, scum and other floating debris (hereafter referred to as ‘pollution’). This pollution can result in pump failures. It has been shown that the occurrence of pump failures has a significant impact on the serviceability of sewer systems such as a 16% increase of the yearly volume of CSO’s. In the current guidelines (e.g. ANSI/HI 9.8-2012) for sump design, guidelines with respect to pollution is only dealt with, in a superficial manner, for a limited number of sump geometries (i.e. trench type and circular sumps). Basically there is a need for a more generic formulation of guidelines. The current guidelines provide optimal hydraulic conditions in the sump and are, to the knowledge of the authors, only verified for clean water sumps. Applying measures to prevent vortices and air entrainment may even result in an increase of the pollution. Therefore, future guidelines should seek for a balanced compromise between avoiding poor flow conditions and air-entrainment on one hand and avoiding the development of pollution on the other hand. Furthermore, experimental data from real wastewater sumps is considered essential for science-based optimised design of wastewater pumping stations. Three classes of experimental parameters have been identified: _ sump geometry; _ pump operation, including capacity and suction level; _ sewage composition. The proposed paper will address all relevant issues and limitations for the set-up of an experimental field campaign. This reflection will result in a comprehensive description of the experimental set-up and possibly an analysis of the first results.

Preventing salt intrusion through shipping locks: recent innovations and results from a pilot setup Otto Weiler 1, Arend Jan van de Kerk 2, Kees-Jan Meeuse 3 1 Deltares 2 Royal HaskoningDHV 3 Rijkswaterstaat - Zee en Delta At many locations, freshwater canals and reservoirs are connected to the sea or estuary by shipping locks. With every passage of a vessel, a lock transports saltwater into the freshwater area, affecting the water quality for consumption, agriculture or industrial application. As a result of climate change, with increased periods of drought, freshwater is becoming increasingly scarce while economic development increases the demand for fresh water. For this reason it is becoming more important to reduce salt intrusion through shipping locks. In the Netherlands there are 23 navigational locks at fresh/saltwater interfaces, of which at present only the Krammer locks have a fully operational salt intrusion prevention system. The current system however is complex, expensive to build and maintain, requires a lot of space and increases locking time significantly. For these reasons this technique is not suitable for implementation at existing locks. An alternative system is sought with a similar level of effectiveness, but without the demands in space, time and costs. One of the traditional ways of preventing salt intrusion is the application of air bubble screens, also known as pneumatic barriers, in the lock heads. Taking this as a starting point, a highly effective combination of measures has been developed, using lab experiments, numerical simulations and field experiments. The new system, referred to as the Delta Salt Barrier System, includes improved air bubble screens, combined with freshwater injection, sills and freshwater flushing of the lock. Also, a computational tool has been developed to predict the salt intrusion for the specific site, conditions and operation. The new system has recently been tested in prototype. For one of the recreational locks at the Krammer lock complex, a pilot installation has been designed and built which has been in operation during the summer of 2014. Measurements have been taken to establish the salt intrusion using different combinations of measures. In general the measures performed as expected, although some new insights were gained as well. Furthermore the pilot has provided important experience on the operational aspects. Supported by the results of the pilot project, it has been concluded that application of the Delta Salt Barrier System would be an attractive alternative for maintenance of the existing system on the Krammer locks.

Bubble plume towed in salt-stratified water Rob Uittenbogaard 1, Scott Socolofsky 2, Yann Friocourt 3, John Cornelisse 4 1 Deltares 2 Texas A&M University 3 Deltares 4 formely Deltares This paper reports on a part of our research on the usage of bubble plumes for reducing the intrusion of seawater in a 15 m deep, salt-stratified tidal channel (the Rotterdam Waterway in The Netherlands). For scaling laboratory experiments, we set the relevant prototype conditions at 15 m depth, 1.5 m/s maximum current, and 1 psu/m maximum salt-stratification with an assumed linear profile. The prime objective of this part of our research is to determine the efficiency of converting (air-compressor) energy into increased potential energy of a salt-stratified current as well as the required air (mass) flux for achieving a given upward salt (mass) transport under prototype conditions. In stagnant density-stratified water, the vertical transport of bubble plumes has been explored mostly through small-scale laboratory conditions; Zic et al. (1990), Lemckert & Imberger (1992) and Asaeda & Imberger (1993) present estimates for the energy efficiency of the bubble plume for upward transport and mixing of denser water in stagnant density-stratified water. For the first time we explore the essential properties of a bubble plume in a salt-stratified current by the equivalent case of a bubble plume towed through salt-stratified stagnant water (typically 10 psu/m) . We conducted laboratory experiments at 0.7 m water depth in a canal at Texas A&M University, USA, and at 2.5 m water depth in Deltares’ 30m long water-soil tank in Delft, The Netherlands; the bubble plume was towed up to 0.4 m/s. From the change in the density profile per tow run of the bubble plume we derive the vertical salt-mass transport of the bubble plume and the energy efficiency. In addition, by using 4 different camera viewing directions, with several different depth levels of dye injection in front of the plume, and by measuring the velocity field around the plume, we observed the plume rise angle, its non-circular cross section, and the general flow pattern. Destratification efficiencies are comparable to and can sometimes exceed values in stagnant stratification.

Water – air bubble screens reducing salt intrusion through ship locks Rob Uittenbogaard 1 1 Deltares A Dutch tradition is the application of air-bubble screens (Bulson, 1961) for reducing salt intrusion through ship locks (Abraham & Van den Burgh, 1962). We define the ratio between the hindered and unhindered salt intrusion (i.e. lock-exchange flow) as Salt-Leak Ratio (SLR). The original air-bubble screens were initiated by releasing compressed air through perforated pipes across the lock floor. Schematic prototype experiments in non-operational ship locks showed that air-bubble screens can reduce the SLR to about 25-30 %. The lack of control over the distribution of the air flux along the perforated pipes¸ marine fouling and neglect in maintenance appeared to increase the SLR to about 50% in operational ship locks. The increasing population and ship/cargo traffic in delta areas as well as the growing demand for more and longer storage of fresh water at lower river discharge invited the following research toward reducing the SLR of air screens to minimal levels. Firstly, across the ship lock, the air is equally distribution by an air duct and series of air regulators each releasing a constant air-mass flux. Secondly, circular diffusers produce air bubbles of optimal size that prevent clustering and undesired openings. Thirdly, the diffusers are mounted in staggered arrangement on two air ducts creating a thick uniformly distributed curtain of air bubbles. This design yielded low SLR in operating locks. Yet the small vertical momentum of water in the air screen’s toe makes that part penetrable for salt water by the baroclinic pressure. Further, unavoidably, air screens entrain salt water and thus mix salt to the fresh-water side. For reducing these salt leaks we added a fresh-water screen at the salt-water side of the air screen. The water screen acts as a sill and reduces the leakage driven by the baroclinic pressure. Finally, the fresh-water of the water screen is mixed into the air screen and partially replaces the entrainment of salt water. Based on observations in a well-instrumented working ship lock (145m length, 14 m width, 5m depth) we present evidence that this combined water - air bubble screen yield the lowest SLR of 0-15 % ever recorded.

Laboratory studies on the response of fine sediment to wind Min Su 1, Peng Yao 2, Zhengbing Wang 3, Yongping Chen 4, Changkuan Zhang 5, Marcel J.F. Stive 6 1 Delft University of Technology 2 Delft University of Technology 3 Delft University of Technology & Deltares 4 College of Harbor, Coastal and Offshore Engineering, Hohai University 5 Hohai University 6 Delft University of Technology To investigate the effects of wind on the suspension of fine sediment, we perform a series of laboratory experiments on a type of in-situ sediments, which was collected from a silty tidal flat of the Jiangsu coast in China. For testing the combined effects of wave and wind, paddle waves are generated with wind blowing on the water surface. Quasi-steady suspensions were obtained under a wide range of wind conditions. Analyses of the suspended sediment concentration reveal that the wind indeed influences the motion of fine sediment, especially under a stronger wind condition. Furthermore, detailed analyses of the velocity in terms of a phase-averaged velocity and turbulence reveal that the response of this sediment to the wind is mainly through suspended load. Turbulence momentum induced by the wind can transport vertically and lead to a longer time sediment suspension. The influence depth depends on the ratio between the wind-induced turbulence and the accompanied attenuation.

Numerical simulation of flow and sediment transport dynamics on the Magdalena River section of Barrancabermeja-La Coquera (Colombia). Jose Oliveros Oliveros 1, Jorge Escobar-Vargas 2, Mohamed Yossef 3, Cesar Cardona 4, Cesar Garay 5, Jorge Sanchez 6, Wendy Ramirez 7, Felipe Ardila 8, Diana Vargas 9 1 CIRMAG - Universidad Javeriana 2 Universidad Javeriana 3 Deltares 4 CIRMAG 5 Cormagdalena 6 CIRMAG 7 CIRMAG 8 CIRMAG 9 Cormagdalena Due to the strategic importance of river transportation on the Magdalena River at the current Colombia´s development plan, Cormagdalena, as managing entity of the Magdalena river basin in Colombia, is building an unsteady numerical model for the flow and sediment transport dynamics for the Magdalena River (Colombia). This work shows the recent advances of a case of study on the river section (Barrancabermeja - La Coquera). The numerical platform is the computer program DELFT 3D which solves the shallow water equations, and the sediment transport equation with a finite difference approximation in three dimensions XYZ. The model is constrained by four boundary conditions, one at the beginning of the computational domain, where a flow discharge is imposed, a second one being an outlet condition, where a free surface elevation is enforced, and two additional flow discharge conditions are imposed, as inlet conditions, to take into account the Sogamoso River, which acts as a tributary. On each case a hydrograph of ten years was developed based on field measurements of climatologic stations in Magdalena and Sogamoso Rivers. Two modeling scenarios, for flow and sediment transport, were established: the first scenario is the modeling of the river natural dynamics, and a second scenario involves the modeling of groynes for the future maintenance of the waterway. From the hydrodynamic results a morphological model was developed based on the Engelund & Hansen, and the Meyer-Peter-Müller equations. A grid independence test was done for each of the simulations, ensuring an optimum distribution of the cells within the computational domain. Results showed that the numerical model approximates qualitatively the current natural conditions, and additionally shows how hydrodynamics changes, and how morphology dynamics evolves on the river when groynes are present within it. Additional analysis are presented where the efficiency of the civil works on the river are assessed to ensure the navigability on that section of the Magdalena River.

Hydraulic modeling of Magdalena River using SOBEK Jorge Luis Sanchez Lozano 1, Felipe Ardila Camelo 2, Jose Javier Oliveros Acosta 3, Wendy Dayana Ramirez Morales 4, Cesar Antonio Cardona Almeida 5, Cesar Ignacio Garay Bohorquez 6, Eelco Verschelling 7, Anke Becker 8, Migena Zagonjolli 9 1 2 3 4 5 6 Corporación Centro de Investigación Científica del Río Magdalena Alfonso Palacio Rudas 7 Deltares 8 Deltares 9 Deltares This paper presents a model of the complex Magdalena River system, as an important step towards knowledge-based river management and flood risk management in Colombia, with due attention for both human and ecosystem interests. Rio Magdalena is the largest river of Colombia. It drains a catchment of 257,000km2 and is home to 38million people. Anthropogenic use of the floodplain areas conflicts with the natural value of these areas. On the one hand there are the extended ecosystems with wildlife species. These natural habitats partly depend on regular river floodings for their continued survival. On the other hand more and more human settlements are constructed in the floodplains, attracted by the many goods and services that the river provides. This has led to a lower acceptance of river related floodings. In the past, decision making with respect to flood management in Colombia has not always been based on sound knowledge of the river system as a whole, but rather on observations at a limited number of locations. To facilitate a transition towards a more knowledge-based decision making process, not only for flood management but also for issues related to navigability, the Magdalena river authority has conducted a research project in order to improve their understanding of this river system. This research project focused on identifying and quantifying the major physical processes responsible for the inundations. For the first time in Colombian history, a numerical model of the entire Magdalena river was constructed and calibrated. The model consists of a one-dimensional component that represents the main channel system and a two-dimensional component for the floodplains and other inundation areas. This model was used to analyze water balances and hydrodynamics during different stages of 2010-2011 period. Different strategies to reduce vulnerability to flooding were evaluated using the model. These steps provided the authorities involved with insight into the physical processes involved in the floodings and the feasibility of the proposed strategies. Furthermore, the modeling endeavor has revealed gaps in data collection and in the organization of the data collection process. This can guide future efforts to improve the model. The numerical model seems to be an ideal tool to facilitate objective and knowledge based discussions with other stakeholders on the management of the river to reconcile wetland requirements and human needs.

SWAN’s underestimation of long wave penetration into coastal systems Jacco Groeneweg 1, Joana van Nieuwkoop 2 1 Deltares 2 Deltares One of the unresolved issues in the spectral wave model SWAN is that wave penetration of swell waves into complex tidal inlets or estuaries is often underestimated by SWAN. Previous studies into this problem revealed that two-dimensional nonlinear interactions, and especially the sub-harmonic interactions could play a major role in the transmission of energy from flats into navigation channels. Since this process is missing in SWAN, this process can explain SWAN’s underprediction of wave energy penetration into a complex tidal inlet system. With this mechanism in mind, it was examined in this study under which conditions SWAN underestimates the wave energy when propagating into complex tidal inlet systems. For this purpose, various existing hindcasts in complex tidal areas have been reanalysed. It was concluded that a mismatch between measured and computed swell energy is often already observed in the tidal inlet for conditions where the ebb-tidal delta is of influence. Whether or not the low-frequency wave energy is underestimated by SWAN is to a large extent determined by the local geometry. For a number of cases it was clearly seen that 2D nonlinear interaction plays an important role. In those cases the waves first propagated over the ebb-tidal delta or tidal flats and subsequently came across a channel. From 2D wave spectra it was seen that the observed waves could enter or cross the channel, whereas the computed waves were refractively trapped to the channel edges.

Long waves in intermediate depths and their influence on the design of nearshore terminals Arne van der Hout 1, Martijn De Jong 2, Frederick Jaouen 3, Olaf Waals 4 1 Deltares 2 Deltares 3 MARIN 4 MARIN Over the last decades the increased use of LNG has resulted in more interest in nearshore terminals. At such terminals this potentially hazardous cargo is not inside a port, nor near a city center. However, long waves (or infragravity waves) present at such relatively exposed locations can lead to excessive vessel motions. This particularly applies to LNG vessels, which show limited motion damping. Numerical methods that can calculate long wave conditions were typically developed and validated for the shallow coastal zone, say

Three-dimensional Arabian Gulf Hydro-Environmental Modeling using Delft3D Tanuspong Pokavanich 1, Yousef Alosairi 2, Reimer de Graaff 3, Robin Morelissen 4, Wilbert Vergruggen 5, Kholood Al-Rifaie 6, Taqi Altaf 7, Turki Al-Said 8 1 Kuwait Institute for Scientific Research 2 Kuwait Institute for Scientific Research 3 Deltares 4 Deltares 5 Deltares 6 Kuwait Institute for Scientific Research 7 Kuwait Institute for Scientific Research 8 Kuwait Institute for Scientific Research The Arabian Gulf (AG) is a semi-enclosed shallow water body surrounded by countries having extreme desertic weather conditions, having the largest coastal developments in the world, seafront industry including the world’s largest power and desalination plants. The AG is facing water quality deterioration from multifaceted stresses, occurring naturally from its poor exchange with the outer sea, as well as cumulative anthropogenic stresses. There is very limited systematic monitoring, knowledge sharing, integrated and cumulative impacts studies and planning for coastal development by the AG surrounded countries. One of the reasons is the absence of generally integrated and holistic tools with which the physical processes and cumulative impacts in the AG can be studied. The objective of this study is to develop a numerical tool to promote better studies and integrated planning among the surrounded countries. This paper presents the development of a three-dimensional hydro-environmental numerical model for the AG using a coupled hydrodynamic model (Delft3D-FLOW) with a biochemical model (Delft3D-WAQ). The coupled model is driven by realistic forcing boundary data derived from different sources e.g., ECMWF ERA-Interim spatial weather data, water temperature and salinity profile timeseries from MyOcean model. The model is validated against field measured data in Kuwait waters. The results of the three-dimensional model will be used to characterize the hydrodynamics and the biochemical features of the AG with a special focus in Kuwait waters. The model will be useful to study cumulative impacts in the entire AG, but can also be applied to generate boundary data for local simulation models for future projects. It is planned to establish an internet forum to advertise existences of the model and promote its usage at the end of the project.

Computational Fluid Dynamics of a bubble curtain for the prevention of salt intrusion at sea locks Thomas O'Mahoney 1, Mike van Meerkerk 2, Aris Twerda 3 1 Deltares 2 TU Delft 3 TU Delft Bubble curtains are a method of reducing salt intrusion at sea locks. In the absence of a bubble curtain a gravity current flow forms as the lock doors are opened owing to the density difference at the interface between salt and fresh water regions. A bubble curtain is a screen of bubbles injected from the canal floor, across the lock opening, forming a hydrodynamic barrier which slows down the exchange of salt water. However, if too much air is injected the screen acts as an effective mixer which increases the amount of salt intrusion. The engineering challenge is to inject enough air into the curtain to slow down salt exchange but not too much that it starts acting as a mixer. A numerical model to predict the required air flow would be a useful tool in bubble curtain design. Bubble curtains are currently installed at the Stevin lock in the Netherlands, among others, and could be installed at a number of other locations in the future where salt intrusion is or becomes a problem. Computational Fluid Dynamics (CFD) is used here with the 3D finite-volume code Star-CCM+ to model a bubble curtain and the results are compared with theoretical results (Abraham & v.d. Burgh, 1962) and experimental results at field scale. A 3D Euler-Euler multiphase fluid model is used for the liquid and air phases. The aim is to validate a numerical tool which can predict the required air injection in the bubble curtain to achieve a desired and given salt reduction factor, a measure of the extent to which the transfer of salt has been reduced from the situation without measures to reduce salt intrusion. The numerical model of the bubble curtain in the absence of slat is compared with experiments (Bulson 1962). Flow velocity profiles are in good agreement at lab scale and field scale. The model is reduced to a computational size which is practical for investigations into the salt exchange flows for locks at field scale. References Abraham, G., and v. d. Burgh, P., 1962, Reduction of salt water intrusion through locks by pneumatic barriers, Delft Hydraulics Laboratory, 28 Bulson, P. S. (1961). Currents produced by an air curtain in deep water. Dock and Harbour Authority Vol. 42, 15-22.

Development of a numerical model to predict the erosion of a dike after the failure of the revetment using time dependent boundary conditions Dorothea Kaste 1, Mark Klein Breteler 2, Yvo Provoost 3 1 Deltares 2 Deltares 3 Rijkswaterstaat The presented work was carried out for WTI2017 (“Research and development of safety assessment tools of Dutch flood defences”) and Projectbureau Zeeweringen (PBZ). The WTI2017 programme is commissioned by the Dutch government to set up new rules and tools for the assessment of the flood protection structures. The goal is to enhance the safety standards in The Netherlands in case of flooding. The PBZ was founded under Rijkswaterstaat (the executive organisation of the Dutch Ministry of Infrastructure and Environment) and Waterschap Scheldestromen (the local water board) almost 20 years ago to take care of the coastal protection systems in Zeeland, in the South of The Netherlands. In the scope of WTI2017, in the subgroup for revetments, a model was set up by Kaste and Klein Breteler (2014) to predict dike erosion under wave attack. The dike erosion model was used to calculate the residual strength of a dike after the failure of the block revetment. It is programmed in Matlab and can also be used in probabilistic calculations. The model was based on erosion formulas by Klein Breteler et. al. (2012), which were derived from large scale physical model tests on the erosion of a dike with a clay layer and a sand core. The erosion during a storm is calculated divided in time steps. The formula for the erosion rate in clay was later enhanced by numerous numerical simulations by Mourik (2014). In close cooperation with PBZ, this numerical model was recently extended by the ability to include a varying water level, such as a storm surge in a tidal area. With the varying water level the wave loading acts on different levels of the dike slope. The challenge hereby was to consider the fact that the erosion of a certain time step depends on the present erosion volume from the previous time steps and it has to be determined what part of the erosion counts into that. The numerical model is especially useful in probabilistic calculations, because it is much faster than an erosion simulation with a numerical model, as e.g. XBeach or ComFlow. Probabilistic calculations with the model were already successfully applied within the WTI2017 project. At the conference, the dike erosion model will be presented with the focus on the recent extension for a varying water level. Furthermore its performance and practical implementation is presented based on a number of test cases.

Developing a transport model for plastic distribution in the North Sea Dana Elena Stuparu 1, Myra van der Meulen 2, Frank Kleissen 3, Dick Vethaak 4, Ghada El Serafy 5 1 Deltares 2 Deltares 3 Deltares 4 Deltares 5 Deltares As a result of the rising plastic usage worldwide, the abundance of plastic litter in the sea and ocean has steadily increased over the last few decades. However, there is considerable uncertainty regarding the occurrence and effects of plastic litter on the marine environment. This uncertainty is visible both at the level of physical impacts but also with respect to the adaptation measures to reduce the negative environmental consequences. Aiming for a better representation of this uncertainty, the EU Marine Strategy Framework Directive was published in 2008 and requires EU member states to achieve ‘good environmental status’ (GES) in Europe’s seas by 2020. The present study aims to improve the knowledge regarding the distribution and hot spots of plastic litter in the North Sea. The litter transport in the North Sea is modeled by further development of the Delft3d software. By combining hydrodynamics with particle tracking concepts, the model calculates how the position of plastic particles evolves in time from their release (discharge from points such as the Rhine or the Meuse) until the end of the simulation. The settling velocity of the particles in the water system is dependent on the ambient conditions (temperature/salinity) and also on the particle characteristics (density/size). Different types (polyethylene, polystyrene, PET, PVC) and sizes (10 µm, 330 µm and 5 mm) of plastics were analyzed. The results demonstrate that density is the main determining factor for plastic settlement and that size also has an effect. Modeling results are then compared with field measurements in sediments. Marine litter is a major threat to the marine environment. In this light, modeling can provide a regional or global overview and advice on clear monitoring questions. This work was funded by the European Union Seventh Framework Programme under grant agreement No 308370 (CLEANSEA project) and the Interreg IVa project MICRO.

Extreme value analysis in typhoon prone areas: case study of the Pearl River estuary Emiel Moerman 1, Reimer de Graaff 2, Joao de Lima Rego 3, Deepak Vatvani 4 1 Deltares 2 Deltares 3 Deltares 4 Deltares Extreme events such as tropical storms and typhoons are often the determining factor for the extreme values of wind, wave and water level conditions. The storm track, its propagation speed, the air pressure drop and the wind speed intensity of a typhoon determine the maximum occurring wave heights, water levels and currents. The stochastic behaviour of typhoons and tropical storms, however, lead to uncertainty in the extreme value analysis, because a slight variation of the typhoon track, propagation speed or wind speed intensity can have a significant impact on these local extreme hydrodynamic conditions. To determine the significance of the stochastic behaviour of typhoons a model assessment is performed comparing standard extreme value analysis values of measured water levels (e.g. values of 1/10, 1/50, and 1/100 year return periods) against model results of artificial typhoons. In the model assessment, making use of Delft3D, various artificial typhoons are modelled in which the typhoon tracks, propagation speeds and wind speed intensities are varied within realistic ranges (based on observed historical typhoons). The study focusses on the Pearl River estuary (China) where typically about 5 to 10 tropical storms or typhoons are observed every year. Once every few years an extreme typhoon hits the area. By quantifying the potential impact of artificial typhoons the uncertainties in the extreme water level values in such a typhoon prone area are better assessed. The model is validated simulating several historic typhoons. Subsequently the typhoons tracks, their propagation speeds and wind speed intensities are varied. The extreme water level values (extreme surge height + mean high water value) that follow from the artificial typhoon modelling are compared against values from a standard extreme value analysis, making use of the central limit theorem for the extreme values in a sample. A Peaks over Threshold approach is applied and the extremes are fitted and extrapolated according to a Generalized Pareto Distribution. One of our main conclusions is that while the peak surge heights and related total water levels resulting from the historical and synthetic typhoon simulations can exceed the once per 100 year extreme total water level estimates, they are generally within the 95% confidence interval of the estimate.

Comparison between the operation of a prototype and a model pump Zbigniew Czarnota 1, Femke Verhaart 2, Anton de Fockert 3 1 Xylem Inc. 2 Deltares 3 Deltares Testing of the approach flow for vertical column pumps for, among others, cooling water, irrigation and storm water is performed according to the ANSI/HI 9.8-2012 standard. Different references are included in this standard on the background of the acceptance criteria, however there is no explicit information on how real pumps respond to swirl, velocity distribution or vortices. In these references limited information is given on the relation between scale models and prototype. Xylem and Deltares have jointly performed a research to determine the relation between scale models and the real pump. At the Deltares pump sump test facility two identical pump compartments were built according to ANSI/HI 9.8-2012 standard. In one compartment a prototype pump (Flygt P7020) was placed, in the other a model of that pump at a scale of 1:1. Measurement of pre-rotation, vortex occurrence, pump vibration, pump efficiency and Q-H curve were performed for different approach flows. By comparing the measurements for the model and the prototype pump the effect of phenomena observed in scale models on prototype pumps is determined. The focus of the research has been on determining the effect of pre-rotation on the pump efficiency. The results of these tests will be presented and discussed during the IAHR world congress.

Numerical modelling of the impact of Sea level rise on large tidal inlet/basin systems Pushpa Dissanayake 1, Harshinie Karunarathna 2, Roshanka Ranasinghe 3 1 College of Engineering, Talbot Building, Singleton Park 2 Swansea University 3 UNESCO-IHE, Deltares, Australian National University Climate change driven sea level rise is very likely to have a significant impact on large tidal inlet/basin systems, including erosion of ebb-tidal deltas and sedimentation of tidal basins, and drowning of tidal flats (Dissanayake et al., 2012). These large inlet/basin systems usually contain extensive tidal flats that are rich in bio-diversity which resultsin major tourist attractions and economic benefits for the local community (De Jong et al.,1999). However, these tidal flats are particularly vulnerable to any rise in the mean sea level. Therefore, a clear understanding of the potential impacts of relative sea level rise on these inlet/basin systems is a pre-requisite for the sustainable management of both the inlet/basin system and the communities that depend on them. In the present study, the response of a large tidal inlet/basin system to Climate change driven sea level rise, in combination with local subsidence is simulated with two very different numerical modelling approaches: process-based (Delft3D) and scale-aggregated (ASMITA). These models are used to simulate the morphological evolution of a schematised inlet/basin system representing the Ameland inlet in the Dutch Wadden Sea for a Relative Sea Level Rise scenario (RSLR) of 10 mm/year over a 25 year period. Though the quantitative forecasts of the two models are different to each other, both models qualitatively indicate, over the 25 year simulation period, (a) a flood-dominant transport system which agrees with the contemporary measurements of the Ameland inlet, and (b) RSLR driven enhancement in the sediment transport. The ASMITA suggests stable tidal flats with an RSLR of 10 mm/year while the tidal flats diminished in the Delft3D.

Open ports for container vessels B. A. Bakermans 1, A. J. van der Hout 2, B. Wijdeven 3 1 Delft University of Technology 2 Deltares 3 Delft University of Technology This paper proposes and evaluates an innovative way of designing container ports, based on MSc –research work carried out at Delft University of Technology, in close cooperation with Deltares. The open port is defined as an offshore and environmentally exposed port. This innovative way of designing ports may be the solution for existing and upcoming problems of large container ports in deltas, such as sedimentation and lack of space. The focus of this present paper is on ports for container vessels. This is because container terminals involve the most stringent criteria on environmental conditions. Traditionally, ports for seagoing container vessels are located in deltas. Main advantage of the location of ports in these deltas is the natural shelter, which is needed for the safe mooring of vessels and for the efficient handling of containers and cargo. Deltas often provide a limited depth and in combination with growing vessel dimensions, dredging costs will generally increase in the future. Moreover, the economic value of deltas becomes higher. Therefore, container ports have no room for expansions and existing ports experience a lot of pressure or public resistance in urbanized regions. Finally, large ports and their breakwaters often have a negative impact on the coastal morphology of deltas. Both morphology and ecology may be disturbed due to a port located in the surf zone of a delta. The idea of an open container port is proposed to avoid these negative consequences of a traditional port layout and location. A technical analysis showed that an exposed container port may be feasible. This relates to recent innovations in mooring techniques and the increasing container vessel dimensions. A potential location for an open container port, Nigeria, is described. A fictitious open port layout was designed based on an offshore reclaimed island. This open port is located at a distance from shore where the natural depth is sufficient for the mooring of the largest container vessels. The analysis showed that the open port concept may be applicable for different situations and conditions.

On the (in)applicability of ANSI/HI 9.8-2012 guidelines at wastewater sump design Alex Duinmeijer 1, Francois Clemens 2, Femke Verhaart 3 1 Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology / Municipality of Rotterdam 2 Water Management Department, Faculty of Civil Engineering and Geosciences, Delft University of Technology / Deltares 3 Deltares An overview is given on the different requirements for the design of pumping stations for respectively clean water and waste water. For clean water the water should be transported as efficient as possible, while avoiding air entrainment. On the other hand, in the transport of wastewater the transport of (floating) solids towards the treatment plant is more important than efficiency. The ANSI/HI 9.8-2012 standard focusses mainly on the design of clean water pumping stations. The authors discuss in this paper which additional requirements should be taken into account in the design of wastewater pumping stations.

Discussion on the acceptance criteria for physical model testing of intake pumping stations Suzanna Zwanenburg 1, Femke Verhaart 2, Anton de Fockert 3 1 Deltares 2 Deltares 3 Deltares The ANSI/HI 9.8-2012 (HIS) is an internationally accepted standard, which provides guidelines and acceptance criteria for the design and testing of intake pumping stations. Besides HIS, also other standards are available like TSJ-S002 (2005). Comparing the acceptance criteria of the different standards, it can be concluded that the feed flow towards the pumps is not consistently judged. For example, where HIS allows a limited pre-rotation angle for proper pump feeding, TSJ-S002 (2005) judges the influence of pre-rotation insignificant for proper pump operation. A scientific basis for the different approaches to the acceptability of the feed flow is not found in literature. Furthermore, the acceptance criteria can be interpreted in multiple ways. The experimental research of Verhaart et al (2014) and de Fockert et al (2014) showed that the acceptability of the feed flow is dependent on the interpretation of the acceptance criteria. In this presentation the drawbacks of the current acceptance criteria will be discussed and ideas to develop new guidelines will be presented. These new guidelines should be based on the relation between the measured phenomena in a model and the performance of the prototype pump.

Morphological evolution of Yangtze Estuary on decadal-scale and its response to human interference Hualong Luan 1, Pingxing Ding 2, Zhengbing Wang 3, Jianzhong Ge 4 1 East China Normal University 2 East China Normal University 3 Delft University of Technology & Deltares 4 East China Normal University Previous studies indicated that Yangtze Estuary (YE) had experienced from sediment accumulation to net erosion in submerge delta front within last half century responding to the reduction of fluvial sediment input caused by upstream dam constructions. The present research analysis the morphological evolution of the entire estuary including tidal channel within estuary and mouth bar area based on historical navigation charts and observed bathymetric maps. Results indicated that the response to human interference (fluvial sediment reduction, engineering works) varied spatially. The mouth bar region was still accumulating sediment after upstream sediment input declined while the tidal channel within YE converted from deposition to erosion especially in shallow area.

Monitoring the impacts of floating structures on the water quality and ecology using an underwater drone Rui P. de Lima 1, Floris C. Boogaard 2, Rutger E. de Graaf 3, Vladislav Sazonov 4, L. Miguel Dionísio Pires 5 1 INDYMO; MARE 2 INDYMO; Tauw; Hanze University of Applied Sciences 3 INDYMO; Deltasync; Rotterdam University of Applied Sciences 4 INDYMO; Deltasync; Rotterdam University of Applied Sciences 5 Deltares Urban delta areas are facing problems related with land scarcity and are impacted by climate change and flooding. To meet the current demands, innovative and adaptive urban developments are necessary. Floating structures are good examples of the flexibility and multi-functionality required to efficiently face the current challenges for delta cities. They offer flood proof buildings, possibilities for water storage and opportunities for sustainable food and energy production. Their impact on the environment, however, is currently unknown and often disregarded. This knowledge gap creates a difficulty for water authorities and municipalities to create a policy framework, and therefore to regulate and facilitate the development of new floating projects. This frequently hinders these kind of initiatives. Monitoring the effects of floating structures on water quality and ecology has been difficult until now because of the poor accessibility of the water body underneath the structures. A remote controlled underwater drone is used equipped with several water quality sensors and a video camera. The drone is guided under floating structures, where it monitors several water quality parameters such as nitrate, conductivity, ammonium, temperature and dissolved oxygen. As a control, the drone also collected data in the open water zone (unaffected by the blockage caused by the floating body). The results show that the current small scale floating structures do not have a significant influence on water quality. Dissolved oxygen levels under and near floating structures remain at acceptable levels. Furthermore, footage from the video camera revealed a multitude of organisms attached to these structures, in addition to fish swimming underneath them. This shows that floating constructions can have a positive effect on the aquatic environment, by creating new habitats and providing shelter for smaller and juvenile fish. Future floating structures projects therefore should be encouraged to proceed.This information is of great value for many (mega) cities (such as London, New York, Manila) where plans are made to build floating structures in the near future.

The 2013 Xaver storm surge and the resilient response of the North Sea defence system Iacopo Carnacina 1, Joao Lima Rego 2, Martin Verlaan 3, Firmijn Zijl 4, Theo Van der Kaaij 5 1 AIR Worldwide 2 Deltares 3 Deltares 4 Deltares 5 Deltares In December 2013 the North Sea experienced one of the major storm surges of the last 100 years, and in some places high waters were higher than for the great 1953 North Sea flood. This makes Xaver an excellent case-study for the validation of the new continental shelf model presented here, which covers a domain form 42S to 63 N and from -15W to 13E. The preliminary results show the adaptation of a previous continental shelf model using a new technology based on flexible mesh. Both tidal propagation and storm surge were calibrated through an automated calibration that accounts for the combination of dozens of roughness and other parameters, which will be used as a base for a new generation of catastrophe models. The new model was validated using data for the recent 5 December 2013 storm. These preliminary results show how the new flexible mesh technology can be adopted for use in such large domains, with the advantage of being able to provide higher resolution depth and surge fields near the coast. Finally, results also showed how flood defenses have been more efficient, providing an excellent example of how risk management policy succeeded in improving the resilience in terms of flood defense, though potential risk for more catastrophic scenarios should not be neglected.

Sharing research data of the sand motor with the openearth datalab Martijn Bakker 1, Kees den Heijer 2 1 3TU.Datacentrum 2 Deltares Increasingly, scientific breakthroughs are powered by advanced online data sharing solutions that help researchers share their datasets. Moreover the speed at which any given scientific discipline advances will depend on how well its researchers collaborate with one another, and with technologists, in areas of eScience such as databases, workflow management, visualization, and cloud computing technologies, as explained in the 4th paradigm. (source: http://research.microsoft.com/en-us/collaboration/fourthparadigm/). Standardisation of an online research environments, called DataLabs, enable researchers of different disciplines to gain access and use each other’s data. A research project depending heavily on its success on multidisciplinary approach is the Sand Motor. The Sand Motor is an innovative method for coastal protection. The Sand Motor (also known as Sand Engine) is a huge volume of sand that has been applied along the coast of Zuid-Holland at Ter Heijde in 2011. Wind, waves and currents will spread the sand naturally along the coast of Zuid-Holland. The Sand Motor will gradually change in shape and will eventually be fully incorporated into the dunes and the beach. The construction of the Sand Motor was completed in November 2011. Now, the forces of nature will take over and spread the sand along the shore, thereby reinforcing the coastline and creating a dynamic area for nature and recreational purposes (source: http://www.dezandmotor.nl/en-GB/). To monitor the success of the Sand Motor, inter disciplinary sharing of research data is crucial. To make this data collaboration possible within the Sand Motor Monitoring projct, a new and innovative online environment was needed. The basis of this environment was the combination of the Open Earth software as designed by Deltares, together with the development of an online portal for storing, editing, sharing and visualisation of geo-related research information. This OpenEarth DataLab has been online since 1st of April 2014 and the project has been evaluated after complete delivery on the first of September 2014. In this presentation the first results of designing, building and working with the DataLab are presented.

Using water age to quantify the hydrodynamic circulation in Lake Taihu using D-Flow Flexible Mesh Sien Liu 1, Qinghua Ye 2, Marcel Stive 3 1 Delft University of Technology 2 Deltares 3 TU Delft Being the third largest freshwater lake and located in one of the most prosperous areas in China, Lake Taihu is suffering from cyanobacteria blooms and severe eutrophication problems. The local government has taken steps to both restrict the sewage effluent of nearby plants and transfer water from Yangtze River to flush Lake Taihu. However, the current ecological condition of Lake Taihu still needs improvement. The lack of knowledge on the lake's hydrodynamic circulation dynamics is a main reason for the deficiency of present improvement measures. The intention of this study is to investigate the hydrodynamic circulation and water exchange in Lake Taihu with the three-dimensional hydrodynamic model, D-Flow Flexible Mesh (D-Flow FM). D-Flow FM is the new computational engine for the unstructured grid in 1D, 2D and 3D. Using the concept of water age, hydrodynamic circulation indices are applied to indicate the circulation efficiency and evaluate the sensitivity of the environmental conditions. Although the hydrodynamics of the lake has been studied quite extensively, virtually no attention has been given to the river network between Lake Taihu and Yangtze River. The hypothesis that the river network is important is supported by the fact that Lake Taihu’s hydrodynamics is strongly influenced by river inflow and outflow discharge from the river network. Thus, the entire Taihu Basin river network is included in the model using D-Flow FM, with the river branches and Lake Taihu in 1D and 2D model. A hydrodynamic model is set up and calibrated with measured data. The water age as the circulation indices is coupled in the hydrodynamic model to quantify the hydrodynamic circulation. Scenarios are designed to test the influence of wind direction, wind speed and evaluate the water transfer plans with the circulation indices. The model results show the significance of wind in the hydrodynamic circulation and its dynamic effects for each subzone in the Lake Taihu. The large scale water transfer from Yangtze River project also helps to improve the water quality to decrease the occurrence of algae bloom in certain subzones of the lake. This study quantifies the water circulation and water exchange by using the hydrodynamic circulation indices as indicators, thus improving the understanding of water circulation of the entire river network. The conclusion of this study will help to understand similar large, shallow lake systems with complicated river network.

Sensitivity of the Sobek 2D Overland Flow Model to change in grid cell size Zahrah Musa 1, Ioana Popescu 2, Arthur Mynett 3 1 Unesco-ihe 2 Unesco-ihe 3 UNESCO-IHE Hydrodynamic models are used in flood modelling to estimate flood peaks, duration, flow time series and flooding extent. One of the most important components of a hydrodynamic model is the topography of the study area which is represented by the grid discretization. Sobek tool of Deltares was used to build the hydrodynamic model of the Niger Delta using SRTM DEM grids to replicate floods that had occurred in 1998, 2005, 2006 and 2007. The model was calibrated using frictional values for the channel and floodplain, and verified based on the 2007 Niger River flood map; and results showed flood location and partially the flood extent. With the availability of surveyed river bathymetry the topography was improved in discretization and the model was recalibrated. The model outputs (like flood peaks, flood extent and modelling time) based on different grid cell sizes show the model sensitivity to changes in the source of topography. A comparison of the two (old and new models) results is undertaken and a sensitivity analysis of the Sobek model to frictional and topographical change is presented. The model calibration conditions are also discussed.

Numerical and physical modelling of different nourishment designs Alessio Giardino 1, Yorick Broekema 2, Jebbe van der Werf 3, Arnold van Rooijen 4, Michalis Vousdoukas 5 1 Deltares, Unit Marine and Coastal System 2 TUDelft 3 Deltares 4 Deltares 5 Joint Research Centre Although the construction of nourishments as coastal protection measure against erosion is becoming common practice in several countries around the world, the design and prediction of the morphological development of nourishments over time is often based on empirical rules and practical experience. This is mainly related to the uncertainties within the currently available numerical models in predicting with sufficient accuracy the hydrodynamics and sediment transport in the surf zone and beach where nourishments are generally applied. In this study, a novel modelling approach was used to simulate the developments of different designs of shoreface and beach nourishments. In particular, a 2DV version of the process-based Delft3D model was used to simulate the hydrodynamics, waves, sediment transport and morphodynamics along cross-shore beach profiles. To account for the effects of short-wave groupiness on the water motion and the accompanying generation of infragravity waves, the “Roller Model” in instationary mode was used (Reniers et al., 2004). Moreover, the spatial and temporal changes in bed composition were computed using multiple fractions and a multi-layered bed stratigraphy. This allows for simulating nourishments with different grain characteristics compared to the native beach sand. The model simulations were validated using a number of lab experiments carried out in the wave flumes of Hannover and Delft, under different erosive and accretive wave conditions. The model shows promising results, both in predicting the morphological development of the nourishments over time (Brier score = “excellent” for not-nourished cases and “good” for nourished cases), and the grain sorting along the beach profiles and adjacent to the nourishment locations. The effect of infragravity waves on the short-wave averaged sediment transport leads to larger peaks in the suspended sediment concentrations. This effect is found essential for a proper representation of the offshore and onshore sediment transport, and the morphological development in case of plane sloping beaches as well as nourished beach profiles.

Reshaping of realistic beach nourishments under high angle wave conditions Bastiaan Huisman 1, Victoria Curto 2, Roderik Hoekstra 3, Matthieu de Schipper 4 1 Delft University of Technology & Deltares 2 Delft University of Technology & Deltares 3 Deltares 4 Delft University of Technology The impact of very obliquely incoming waves (i.e. larger than 45° with respect to the shore-normal) on the morphology of nourishments has been investigated in literature using either a one-line approach or quasy-2D models. Typically, these studies predicted downdrift nourishment migration and the generation of alongshore sand waves for coasts with persistent high-angle wave conditions. The size of the nourishments or the cross-shore profile shape applied in these studies is however much larger than what is common for the Dutch coast. This research therefore aims at exploring the reshaping mechanisms of beach nourishments of realistic Dutch proportions as a result of high-angle waves. To this end a Delft3D numerical model study was performed testing two conceptual nourishment configurations of 2 km long and a cross-shore extent of respectively 250m or 1000m. First, the numerical model was applied to provide a qualitative indication of the impact of high-angle waves by examining the spatial patters of wave height and direction as well as the initial alongshore sediment transport fields. These computations show that for the Dutch coast situation nourishments with a relatively small cross-shore perturbation (250m width and 2km length) are not likely to develop high-angle wave instabilities even for continuous very obliquely incoming waves. As the initial sediment transport patterns indicate that instabilities might be present for large nourishments (1km width and 2km length) the latter case was tested more rigorously with a morphodynamic simulation. These simulations show that indeed some lee side effects could be expected for continuous high angle waves. Further investigation with alternating low angled and high angled waves, revealed that the sequencing and frequency of the high angled waves can be of importance. Although large nourishments can migrate downdrift during high-angle wave conditions and generate some leeward erosion, a relatively short period with low-angle waves can wipe out the features of the leeward erosion.

Wave–current interaction study along Gulf of Khmbhat, India Balaji Ramakrishnan 1, J. Satheeshkumar 2 1 Indian Institute of Technology Bombay 2 IIT Bombay In past few years, process-based numerical models are widely recognized as a valuable tool for coastal and oceanic processes. Even long-term prediction models are used by many research institute and industries. Gulf of Khambhat is situated in the west coast of India which is strongly influenced by tidal hydrodynamics compare to any other coasts in India. The tidal hydrodynamics along the gulf is so complex due to its geometry, amplification of tidal amplitudes. In the present study, depth-averaged numerical model have been developed to understand the tidal hydrodynamics along the gulf using Delft–3D (Deltares, 2013) numerical scheme. The boundary conditions for the numerical model were extracted from the global tidal models. It is estimated that the tidal range varies from 2m at offshore locations to more than 9m at the end of the gulf. At some locations, the tide induced currents were estimated to be of the order of about 3ms-1. To ensure the influence of tides on the wave characteristics, a coupled numerical model was also developed and the results showed significant variations of water level and velocity due to the wave effect. The details of numerical models, methodology and results are discussed in this paper. Keywords: Tidal hydrodynamics, wave-current interaction, Gulf of Khambhat, Delft-3D

Effect of vegetation on floods: the case of the river Magra Andrés Vargas-Luna 1, Riccardo Benifei 2, Luca Solari 3, Gertjan Geerling 4, Mijke van Oorschot 5 1 Delft University of Technology 2 University of Florence 3 Department of Civil and Environmental Engineering, University of Florence 4 Deltares 5 Deltares The study of the influence of vegetation on hydraulic risk is of primary importance in river planning and decision making. In this work, we investigate the effects of channel and riparian vegetation on the catastrophic flood event that occurred on 25/10/2011 in the river Magra, (Tuscany region, Italy). This 200-year-return-period flood had produced the loss of many human lives and enormous material damages, especially in the town of Aulla. Preliminary hydraulic studies, carried out with 1D models, showed that riparian vegetation located on the floodplain strongly influenced the flood by increasing the water levels of about 0.8 m in the river reach facing the town of Aulla, thus producing overflow of the embankments and flooding of large urbanized areas. Based on these results, the Tuscany region decided to remove the floodplain vegetation as a preventive action. Ecological damages and major changes in river morphodynamics were reported after removing the riparian vegetation. This work addresses the effectiveness of different flood mitigation strategies by using a more detailed hydrodynamic model, i.e. the 2D morphological model Delft3D which includes a sub-model for evaluating the presence of various species of vegetation in different areas of the river.

Comparison of three bed form models to predict roughness for operational flood modeling Jord Warmink 1, Suleyman Naqshband 2, Olav J M van Duin 3 1 University of Twente 2 University of Twente 3 Operational water management department, Deltares The hydraulic roughness of the main channel of most lowland rivers is dominated by bed forms. River bed forms act as roughness to the flow, thereby significantly influencing the water levels, which are essential for flood forecasting. We compared a time-lag model and a physically based pickup and deposition model to predict dynamic bed form evolution during a flood wave in the flume and the field. The results showed that the explicit computation of bed form and associated roughness predictions perform equally well as a calibrated model for the flume case, but slightly less for the field case. We were able to explain a large part of the roughness of the main channel that is normally calibrated and explicitly account for the hysteresis effect. Calibration will always remain necessary, but using the knowledge of bed form evolution and including this in the prediction can largely improve the accuracy of water level predictions, especially in circumstances where calibration data is scarce.