19_058_2 FHR reports
Validation of North Sea models Sub report 2 The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary
www.flandershydraulicsresearch.be
Validation of North Sea models Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary
Chu, K.; Vanlede, J.; Smolders, S.; Decrop, B.; Mostaert, F.
Cover figure © The Government of Flanders, Department of Mobility and Public Works, Flanders Hydraulics Research Legal notice Flanders Hydraulics Research is of the opinion that the information and positions in this report are substantiated by the available data and knowledge at the time of writing. The positions taken in this report are those of Flanders Hydraulics Research and do not reflect necessarily the opinion of the Government of Flanders or any of its institutions. Flanders Hydraulics Research nor any person or company acting on behalf of Flanders Hydraulics Research is responsible for any loss or damage arising from the use of the information in this report. Copyright and citation © The Government of Flanders, Department of Mobility and Public Works, Flanders Hydraulics Research 2020 D/2020/3241/202 This publication should be cited as follows: Chu, K.; Vanlede, J.; Smolders, S.; Decrop, B.; Mostaert, F. (2020). Validation of North Sea models: Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary. Version 3.0. FHR Reports, 19_058_2. Flanders Hydraulics Research: Antwerp. IMDC: I/RA/11502/20.106/KCH/ Reproduction of and reference to this publication is authorised provided the source is acknowledged correctly. Document identification Customer: Keywords (3-5): Knowledge domains Text (p.): Confidentiality:
afdeling Maritieme Toegang Ref.: WL2020R19_058_2 Hydrodynamics; North Sea model; Scheldt; SLR Hydraulics and sediment > Hydrodynamics > Tides > Numerical modelling 37 Appendices (p.): 2 ܈No ܈Available online
Author(s):
Chu, K.; Vanlede, J.
Control Name Reviser(s):
Project leader:
Decrop, B.; Smolders, S.
Vanlede, J.
Signature Boudewijn Decrop (Signature)
Digitally signed by Boudewijn Decrop (Signature) Date: 2021.01.04 11:20:47 +01'00'
Getekend door:Sven Smolders (Signatur Getekend op:2021-01-08 08:48:51 +00:0 Reden:Ik keur dit document goed
Getekend door:Joris Vanlede (Signature) Getekend op:2021-01-22 10:27:25 +01:0 Reden:Ik keur dit document goed
Approval Getekend door:Frank Mostaert (Signature Getekend op:2021-01-04 11:49:05 +00:0 Reden:Ik keur dit document goed
Head of Division:
F-WL-PP10-2 Version 7 Valid as from 3/01/2017
Mostaert, F.
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary
Abstract The influence of Sea Level Rise (SLR) on the tidal characteristics in the North Sea and in the Scheldt estuary is evaluated in a scenario analysis for three scenarios of SLR: 1 m, 2 m and 3 m respectively. DCSMv6-ZUNOv4 and SCALDIS are selected as the modelling instruments. The models are run for 2 spring-neap cycles in 2015 without wind and pressure forcing (purely harmonic run). In the North Sea, the M2 tidal amplitude increases in the Southern Bight under SLR. Along the Belgian coast, the M2 amplitude increases with 2 cm, 4 cm and 6 cm with SLR of 1 m, 2 m and 3 m. The M2 tidal phase decreases, consistent with the faster propagation of the tidal wave in deeper water. The southern amphidromic point (closest to the Belgian Coastal Zone - BCZ) is expected to move north-eastwards with SLR of 1 and 2m. In the scenario of SLR of 3m, the amphidromic point shifts to the north-west. In the Scheldt Estuary, the changes on high water level are generally in proportion to the SLR of 1m, 2m and 3m. However the high water level drops in the Upper Sea Scheldt, mainly because the overflowing dikes of the Flood Control Areas (FCA’s) are represented in the model mesh, and the depoldered areas become drowned with SLR. Note that this corresponds to an initial response without autonomous development. In reality, SLR will not occur overnight, and the estuarine morphology will change on a longer timescale. The redistribution of sediments (erosion/deposition) will modify the hydrodynamics in the estuary, which in turn will change the morphology in a feed-back loop that is difficult to model accurately. The tidal asymmetry along the thalweg is evaluated based on tidal duration (falling/rising, ebb/flood) and velocities (maximum and mean) under different SLR scenarios. With SLR the initial effect in the estuary is that it becomes less ebb-dominant in terms of duration asymmetry upstream of km 100 (more equal timing of periods of ebb and flood). But the estuary becomes more ebb-dominant in terms of velocity asymmetry. The different results for different definitions of tidal asymmetry does not allow a straightforward interpretation in terms of expected morphological response, and warrants future research, e.g. with a sediment transport model.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary
Contents Abstract ............................................................................................................................................................ III Contents ............................................................................................................................................................ V List of tables...................................................................................................................................................... VI List of figures ................................................................................................................................................... VII 1
Introduction ............................................................................................................................................... 1
2
Methodology ............................................................................................................................................. 2
3
Model instruments .................................................................................................................................... 3
4
5
3.1
DSCMv6-ZUNOv4 ............................................................................................................................... 3
3.2
SCALDIS 2013 ..................................................................................................................................... 4
Effect of SLR in the North Sea.................................................................................................................... 8 4.1
Co-tidal maps ..................................................................................................................................... 8
4.2
Water Level Timeseries ................................................................................................................... 10
4.3
Harmonic Analysis of Water Levels ................................................................................................. 15
Effect of SLR in the Scheldt estuary ......................................................................................................... 20 5.1
Water level timeseries ..................................................................................................................... 20
5.2
Harmonic analysis of water levels ................................................................................................... 23
5.3
Analysis of tidal asymmetry............................................................................................................. 28
5.4
Inundation of Flood Control Areas .................................................................................................. 31
6
Conclusions .............................................................................................................................................. 36
7
References ............................................................................................................................................... 37
Appendix A
Definition of Statistics.............................................................................................................. A1
Appendix B
Comparison between ZUNOv4 and SCALDIS ........................................................................... A2
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List of tables Table 1 – Parameter settings of DCSM-v6-ZUNOv4. ......................................................................................... 4 Table 2 – Model parameters SCALDIS model. ................................................................................................... 5 Table 3 – List of all Sigma areas, their future function and if they are included in the SCALDIS model ........... 6 Table 4 – Statistics of the effect of SLR on high and low water (both level and time) as observed in ZUNOv4. ......................................................................................................................................................................... 14 Table 5 – Changes of M2, S2 and M4 tidal amplitude and phase due to SLR as observed in ZUNOv4. .......... 16 Table 6 – Bias of high-low water and high-low water time with SLR (SCALDIS). ............................................ 23 Table 7 – Effect on M2, S2 and M4 tidal amplitude and phase due to SLR (SCALDIS). ................................... 24 Table 8 – Results comparison at Vlissingen between ZUNOv4 and SCALDIS. ................................................. A2
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List of figures Figure 1 – Overview of the DCSMv6-ZUNOv4 hydrodynamic model grids ....................................................... 3 Figure 2 – Bathymetry of the SCALDIS model ................................................................................................... 5 Figure 3 – M2 tidal amplitude and phase of the Base run (without SLR).......................................................... 8 Figure 4 – Influence of SLR (1m, 2m and 3m) on M2 tidal amplitude in the North Sea. .................................. 9 Figure 5 – M2 tidal phase under different scenarios with shift of amphidromic points................................. 10 Figure 6 – Location of water level stations in the North Sea. ......................................................................... 11 Figure 7 – Response of high water level to SLR. .............................................................................................. 12 Figure 8 – Response of low water level to SLR. ............................................................................................... 12 Figure 9 – Response of high water level time to SLR. ..................................................................................... 13 Figure 10 – Response of low water level time to SLR...................................................................................... 13 Figure 11 – Example of water level predicted at Vlissingen with and without SLR. ....................................... 14 Figure 12 – M2 amplitude with SLR as observed in ZUNOv4. ......................................................................... 17 Figure 13 – M2 phase with SLR as observed in ZUNOv4. ................................................................................ 17 Figure 14 – S2 amplitude with SLR as observed in ZUNOv4. ........................................................................... 18 Figure 15 – S2 phase with SLR as observed in ZUNOv4................................................................................... 18 Figure 16 – M4 amplitude with SLR as observed in ZUNOv4. ......................................................................... 19 Figure 17 – M4 phase with SLR as observed in ZUNOv4. ................................................................................ 19 Figure 18 – Response of high water level to SLR. ............................................................................................ 21 Figure 19 – Response of low water level to SLR. ............................................................................................. 21 Figure 20 – Response of high water time to SLR. ............................................................................................ 22 Figure 21 – Response of low water time to SLR. ............................................................................................. 22 Figure 22 – M2 amplitude with SLR. ................................................................................................................ 25 Figure 23 – M2 phase with SLR........................................................................................................................ 25 Figure 24 – S2 amplitude with SLR. ................................................................................................................. 26 Figure 25 – S2 phase with SLR. ........................................................................................................................ 26 Figure 26 – M4 amplitude with SLR. ................................................................................................................ 27 Figure 27 – M4 phase with SLR........................................................................................................................ 27 Figure 28 – Thalweg along the Scheldt in grey (resolution of 1 km). .............................................................. 29 Figure 29 – Duration asymmetry. .................................................................................................................... 30 Figure 30 – Velocity asymmetry. ..................................................................................................................... 30 Figure 31 – Time series of water level predicted by SLR0m at Antwerp. ....................................................... 31 Figure 32 – Depth difference under SLR. The black lines indicate the FCAs. .................................................. 31
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Figure 33 – Depth difference under SLR. Zoom into FCA of Grensgebied, Hedwigepolder en Doelpolder. ... 32 Figure 34 – Depth difference under SLR. Zoom into FCA of Burchtse Weel en KBR. ...................................... 32 Figure 35 – Depth difference under SLR. Zoom into FCA of Oudbroekpolder, Schellandpolder, HingeneBroekpolder, Spierbroekpolder, Groot Schoor, Stort Hingene, Stort Ballooi en Schouselbroek. ..... 32 Figure 36 – Depth difference under SLR. Zoom into FCA of Tielrodebroek, De Bunt, Lippenbroek. .............. 33 Figure 37 – Depth difference under SLR. Zoom into FCA of Klein Broek en Groot Broek. .............................. 33 Figure 38 – Depth difference under SLR. Zoom into FCA of Potpolder I en Polder van Waasmunster. ......... 33 Figure 39 – Depth difference under SLR. Zoom into FCA of Potpolder IV....................................................... 34 Figure 40 – Depth difference under SLR. Zoom into FCA of Blankaart, Zwijn, Grote Wal en Kleine Wal, Uiterdijk, Vlassenbroek I en Vlassenbroek II. .................................................................................................................. 34 Figure 41 – Depth difference under SLR. Zoom into FCA of Scheldebroek, Paardeweide en Bergenmeersen. ......................................................................................................................................................................... 34 Figure 42 – Depth difference under SLR. Zoom into FCA of Wijmeers I en Wijmeers II, Bastenakkers en Ham. ......................................................................................................................................................................... 35 Figure 43 – Depth difference under SLR. Zoom into FCA of Zandput Melle en Heusden. .............................. 35
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1 Introduction Within the framework of the research program “Agenda voor de Toekomst II”, Flanders Hydraulics is performing research on the topic of Sea Level Rise (SLR). As a first step, we validated the different available North Sea model schematisations for the year 2015 with regards to their hindcasting performance at calculating water levels in the Belgian Coastal Zone (Chu et al., 2020). In this report, different scenarios of SLR are performed to explore the effects of SLR on tidal hydrodynamics in the Belgian part of the North Sea and the Scheldt estuary. DCSMv6-ZUNOv4 and SCALDIS are selected as the modelling instruments. The changes on water level time series (high/low water and their timing) due to SLR are statically compared at coastal stations in the North Sea and conventional stations along the Scheldt estuary. The impact on harmonic components (M2, S2, M4) are intercompared as well. In the Scheldt estuary, the changes on tidal asymmetry due to SLR are systemically analyzed.
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2 Methodology Taal (2019) studied the tidal changes in the Netherlands due to SLR. The research evaluated the influences of SLR on tide including high water and low water. Two scenarios of SLR were defined as below, where RCP (Representative Concentration Pathway) represents the greenhouse gas concentration (not emissions) trajectory adopted by the IPCC. For instance RCP4.5 is a scenario that stabilizes radiative forcing at 4.5 W/m2 in the year 2100 without ever exceeding that value.
Muis et al (2019) combined GTSM3.0 with probabilistic SLR projections that include an increased contribution from Antarctica. The 50th and 95the SLR projection for RCP8.5 indicate sea levels that are respectively 1.8m and 2.9 m higher by 2100. Following the scenarios defined above, three scenarios of SLR are simulated in this study, the SLR of 1 m, 2 m and 3 m respectively. The effect of SLR are added to the mean sea level constantly at the open boundaries of the DCSMv6- ZUNOv4 model. Note that in reality, the SLR might be spatially non-uniform. For future studies, it is recommend to derive spatial-varying SLR for the boundary of DCSM from a global tidal model (e.g. GTSM of Deltares). Using boundary nesting, the effect of SLR is further transferred from the North Sea to the Scheldt estuary with the SCALDIS 2013 model. The effect of SLR is evaluated against a reference run (SLR = 0 m) which corresponds to the current situation of the estuary. The model train is run for a period of two spring-neap cycles (16/08-13/09) in the year 2015. The model train is run with harmonic boundary conditions and without wind and pressure. Sediment transport and morphology are not included in the present study. All flood control areas (FCA’s) that are currently active, planned or decided are included in the SCALDIS model grid. Note that the culvert functionality is switched off in this study to save calculational time. This implies that the CRT function (Controlled Reduced Tide) is not active. But water can still flow over the overflow dike which mean the areas still function as a Flood Control Area (FCA). The current situation (SLR of 0 m) is taken as the reference model, the influence of SLR of 1 m, 2 m and 3 m are evaluated by directly comparing with SLR of 0 m. In such a way, the relative influence of SLR can be accurately interpreted without considering the model accuracy of the reference model.
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3 Model instruments 3.1 DSCMv6-ZUNOv4 DCSMv6 – ZUNOv4 has been developed at Deltares as an application of WAQUA in SIMONA, a framework for hydrodynamic modelling of free-surface water systems (Zijl, 2013). The DCSMv6-ZUNOv4 model consists of two separate domains coupled together by means of horizontal domain decomposition. Figure 1 demonstrates the computational model grid. Table 1 lists the general settings of DCSMv6 and ZUNOv4. The details of model setup and performance of DCSMv6-ZUNOv4 are described in Chu et al (2020). The calibration results reveal that the DCSMv6-ZUNOv4 model yields an overall RMSE of 9.2 cm for water level, which is very decent. When zoom in to the Belgian coast, the averaged RMSE of water level is 8.6 cm (more details are provided in Chu et al., 2020). Figure 1 – Overview of the DCSMv6-ZUNOv4 hydrodynamic model grids, with the DCSMv6 domain in green and the ZUNOv4 domain in blue.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Table 1 – Parameter settings of DCSM-v6-ZUNOv4.
Settings
DCSM-v6
ZUNO-v4
Grid resolution
1.5’ in east-west direction and 1.0’ in 25-500 m nearshore and 2-3 km north-south direction (2×2 km), with a offshore. refinement in the southern North Sea and Dutch coastal waters.
Number of grid cells
1120 in east-west direction and 1260 in 1448 in east-west direction and 637 in north-south direction. north-south direction.
Open boundary 1. Water level defined by 38 tidal Calculated by DCSM-v6 via domain condition constituents. decomposition. 2. non-tidal effect of local pressure is considered with inversed barometer correction Coordinate system
WGS84 geographical
Time Zone
GMT
Roughness
Spatial varying Manning values determined by automatic calibration with OpenDA
Tide generating force Components of the tide with a Doodson number from 55.565 to 375.575 are included. Wind
Spatial (~10×10 km) and temporal (hourly) varying wind field data from Hirlam (v7.2). Charnock coefficient = 0.025.
Drying and flooding
Threshold value of 0.1 m.
Vertical reference
MSL
Time step
1 mins
3.2 SCALDIS 2013 The SCALDIS 2013 model (developed in TELEMAC-3D) has been recently validated for the year 2015 by Chu et al. (2017). Figure 2 demonstrates the model domain and bathymetry. Table 2 listed the general settings of the model. More details of the model can be found in Chu et al (2017). The SCALDIS model was systematically validated against water level, salinity and velocities (both stationary and ADCP sailed data throughout the Scheldt). Compared with NEVLA3D model, SCALDIS shows better performance on velocity predictions in the upper sea Scheldt. All flood control areas (FCA’s) that are currently active, planned or decided are included in the SCALDIS model grid. A shapefile with the Sigma contour lines (version April 2015) was used as described by Smolders et al (2016). Areas assigned as wetlands are not included in the SCALDIS model as they lay outside the Sigma dikes. FCA’s planned in the future are included in the SCALDIS model mesh except the areas that were assigned to be reserve areas (=Blankaart, Hingene Broekpolder, Spierbroekpolder, Heindonk Tien Vierendelen II and Battenbroek). Table 3 gives a list of all areas with their function and if they are included in the model. The FCA’s were modelled in the original SCALDIS model by culvert which is a combination of sink and source term. The background and theoretical description of the culvert functionality in SCALDIS are referred to Smolders et al (2016) and are not elaborated in this report.
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It is noteworthy that switching on all the culvert will slow down the computation time by a factor of 4.5. As we are modelling a calm period of August 2015 during which the FCA’s are not activated as used for stormy period. Therefore the functionality of culvert are switched off in this study. Figure 2 – Bathymetry of the SCALDIS model (positive downward).
Table 2 – Model parameters SCALDIS model.
Parameter
Value
Parameter
Time step
4s
Initial condition
1 m NAP
Number of vertical levels
5
Salt transport
Off
Wind
Off
Bed roughness
Space-varying roughness field with Manning coefficient
Option for the treatment of tidal flats 1: equations solved everywhere with correction on tidal flats Treatment of negative depths
2: flux control
Free surface gradient compatibility
0.9
Vertical turbulence model
2: mixing length
Mixing length model
3: Nezu and Nakagawa
Horizontal turbulence model
4: Smagorinski
Scheme for advection of velocities
1: characteristics
Scheme for advection of depth
5: conservative scheme
Scheme for advection of tracers
13: Leo Postma for tidal flats
Scheme for diffusion of velocities
1: implicit (1 is default; 0 cancels the diffusion)
Scheme for diffusion of tracers
1: implicit
Solver
7: GMRES
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Table 3 – List of all Sigma areas, their future function and if they are included in the SCALDIS model
Area Grensgebied N-Prosperpolder Doelpolder Noord en Midden Potpolder van Lillo Fort Filip Burchtse weel Kruibeke Bazel Rupelmonde Oud Broekpolder Schellandpolder Hingene Broekpolder Spierbroekpolder Groot Schoor (Bornem) Stort van Hingene Stort Ballooi Schousselbroek Tielrode Broek De Bunt Klein Broek Groot Broek Potpolder I Weijmeerbroek en Oude Durme Polder van Waasmunster Bulbierbroek Hof ten Rijen Zuidelijke vijver Hof ten Rijen Potpolder IV Potpolder V Nonnengoed Putten van Ham Hagemeersen Lippenbroek Blankaart Zwijn Groot Schoor (Hamme) Grote Wal – Kleine Wal Vlassenbroekse polder 1 Vlassenbroekse polder 2 Uiterdijk Scheldebroek Paardebroek Paardeweide Bergenmeersen Wijmeers 1
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Function addition de-embankment CRT soil remediation de-embankment addition FCA/CRT FCA FCA FCA (reserve) FCA (reserve) de-embankment de-embankment soil remediation FCA/CRT FCA/CRT FCA/CRT de-embankment de-embankment de-embankment wetland de-embankment wetland wetland wetland FCA/wetland wetland wetland wetland wetland FCA/CRT FCA (reserve) FCA de-embankment FCA FCA/CRT FCA de-embankment FCA wetland FCA/wetland FCA/CRT FCA
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In the model? yes yes yes yes yes yes yes yes yes no no yes yes yes yes yes yes no no yes no yes no no no yes no no no no yes no yes yes yes yes yes yes yes no yes yes yes
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Area Wijmeers 2 Kalkense Meersen Ham Bastenakkers Zandput Melle Heusden Stort de Naeyer Bovenzanden Heindonk – Tien Vierendelen (deel1) Heindonk – Tien vierendelen (deel 2) Zennegat – Oude Dijlearm Grote Vijver 1+2 Battenbroek Schonenberg Rijmenam Pikhaken Hollaken – Hoogdonk deel 1 Hollaken – Hoogdonk deel 2 Anderstadt 1 Anderstadt 2 Anderstadt 3 Vijvers Hof van Lachenen Polder van Lier Mondingsgebied Grote Nete Varenheuvel - Abroek Herinrichting Grote Nete Dorent
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Function de-embankment wetland FCA/CRT FCA de-embankment de-embankment Afgraven FCA/CRT FCA FCA (reserve) FCA/CRT FCA/CRT/addition FCA (reserve) dike allocation FCA wetland FCA
In the model? yes no yes yes yes yes yes yes yes no yes yes no yes Yes no yes
FCA
yes
de-embankment FCA wetland wetland FCA wetland wetland dike allocation wetland
yes yes no no yes no no no no
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4 Effect of SLR in the North Sea The influence of SLR on the North Sea is evaluated in this chapter, based on modelling results from DCSMv6ZUNOv4. The co-tidal maps are intercompared under different SLR scenarios. The time series of water level at coastal stations in the North Sea are analyzed both in the time domain (bias of high/low water) and frequency domain (harmonic components).
4.1 Co-tidal maps The most dominant tidal constituent in the North Sea is the M2-tide. Figure 3 presents the M2 tidal amplitude and phase without SLR. Figure 3 – M2 tidal amplitude and phase of the Base run (without SLR).
Pickering et al (2012) investigates the effect of future SLR (2 m and 10 m) on the tides of the northwest European Continental Shelf. He found that the M2 tidal amplitude responds to SLR in a spatially non-uniform manner, with substantial amplitude increases and decreases in both scenarios. The M2 tidal response is nonlinear between 2 and 10 m with respect to SLR, particularly in the North Sea. Figure 4 shows the changes of M2 tidal amplitude due to future SLR of 1m, 2m and 3m. The M2 amplitude declines at the coast of Holland and part of the eastern British coast while it increases in the Southern Bight domain. The pattern is more profound with larger SLR. These model results are in a line with the findings of Pickering et al. (2012).
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 4 – Influence of SLR (1m, 2m and 3m) on M2 tidal amplitude in the North Sea. Top panel: over view. Bottom panel: zoom in to the BCZ. Red/blue color indicate increase/decrease of M2 tidal amplitude with SLR.
Figure 5 shows the effect on M2 tidal phase of SLR. The southern amphidromic point in the North Sea (closest to the Belgian Coastal Zone (BCZ)) moves north-eastwards consistently by 3.6’ (~ 4.5 km), 1.8’ (~ 2.8 km) and 4.2' (~ 5.4 km) along with SLR of 1 m, 2 m and 3 m. The northern amphidromic point in the North Sea shifted north-eastwards significantly by 7.8’ (~ 9.1 km) with SLR of 1m. It moves further to the east by 2.8’ (~ 3 km) with SLR of 2m. Afterwards it moves to an opposite direction of North-West by 2.0’ (~ 2.4 km) with SLR of 3m. This North-Westerly shift of the northern amphidromic point for higher values of SLR was also reported by Pickering et al. (2012) for a run with SLR of 10 m. Note that Pickering et al (2012) only report on SLR scenarios of 2m and 10m, so their results are not one-on-one comparable with the results in this report.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 5 – M2 tidal phase under different scenarios with shift of amphidromic points.
4.2 Water Level Timeseries Figure 7 to Figure 10 illustrate the changes of high and low water level and time due to SLR. The statistics are presented in Table 4. The location of water level stations in the North Sea is shown in Figure 6. The changes on high water level are generally in proportion to the SLR of 1m, 2m and 3m.The changes on low water level are generally in proportion to the SLR at the British and French coast. However along the Belgian and Dutch coast the low water level is less increased compared with the assigned values of SLR. For instance, at Belgian coast the low water levels are increased by 0.97, 1.95 and 2.92 m respectively with SLR of 1, 2 and 3 m. The low water levels are even less increased in the Scheldt estuary (0.93, 1.89 and 2.86 m to SLR of 1, 2 and 3 m). This is consistent with the rise in tidal amplitude that is described in chapter 4.3. In general the tides propagate faster with SLR. Along the Belgian coast the high water times are 7, 12 and 19 minutes in advance due to SLR of 1, 2 and 3 m, respectively. The low water travels even faster by 10, 19 and 27 mins. Note that the effect on timing of HW is different from the effect on timing of LW, which implies a change in the shape of the tidal curve due to SLR. Figure 11 exemplifies the water level predicted at Vlissingen, illustrating the faster propagation speed with SLR.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 6 – Location of water level stations in the North Sea.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 7 – Response of high water level to SLR.
Figure 8 – Response of low water level to SLR.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 9 – Response of high water level time to SLR.
Figure 10 – Response of low water level time to SLR.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 11 – Example of water level predicted at Vlissingen with and without SLR.
Table 4 – Statistics of the effect of SLR on high and low water (both level and time) as observed in ZUNOv4.
High Water Level [m]
UK
FRANCE
Belgian Coastal Zone
14
Leith North Shields Whitby Immingham Cromer Lowestoft Harwich Sheerness Dover Newhaven Portsmouth AVERAGE CHERBOURG LEHAVRE BOULOGNE-SURMER CALAIS DUNKERQUE AVERAGE Westhinder Nieuwpoort Oostende Cadzand Vlakte van de Raan Westkapelle AVERAGE
Low Water Level [m]
SLR1 SLR2 SLR3 SLR1 SLR2 SLR3 m m m m m m 1.01 1.98 2.95 1.01 2.00 2.94 1.02 2.02 3.01 0.98 1.98 2.98 1.01 2.01 3.01 1.00 2.01 3.02 0.88 1.84 2.84 1.04 2.13 3.26 1.00 1.99 2.97 1.01 2.04 3.06 1.02 2.04 3.07 0.97 1.94 2.92 1.03 2.06 3.09 0.96 1.94 2.93 1.10 2.08 3.08 1.01 2.04 3.05 1.00 2.04 3.06 0.98 1.97 2.95 1.02 2.04 3.07 0.96 1.93 2.89 1.08 2.10 3.12 1.03 2.05 3.02 1.02 2.02 3.02 1.00 2.00 3.00 0.95 1.90 2.84 1.02 2.04 3.06 1.04 2.01 2.98 1.00 2.02 3.03 1.01 1.01 1.00 1.00 1.01 1.00 1.00 1.00 1.00 1.00 1.00
1.99 2.03 2.02 1.99 2.03 2.02 2.02 2.01 2.01 2.01 2.02
2.98 3.04 3.04 2.98 3.06 3.05 3.06 3.03 3.04 3.04 3.05
0.99 0.99 0.99 1.00 0.97 0.97 0.97 0.97 0.97 0.96 0.97
1.98 1.98 1.99 2.00 1.95 1.95 1.95 1.96 1.95 1.93 1.95
WL2020R19_058_2
2.98 2.98 2.99 3.01 2.92 2.93 2.93 2.94 2.92 2.89 2.92
High Water Level Time Low Water Level Time [min] [min] SLR1 SLR2 SLR3 SLR1 SLR2 SLR3 m m m m m m -14 -23 -11 0 4 0 -6 -9 -10 -4 -6 -7 -4 -7 -7 -3 -6 -6 -3 2 1 -8 -11 -16 -6 -12 -16 -7 -12 -18 -7 -13 -19 -4 -14 -18 -10 -19 -29 -7 -15 -21 -27 -45 -62 -10 -19 -29 -1 -3 -17 -8 -17 -24 -4 -4 -14 -4 -8 -13 -11 -19 -14 -6 -1 -6 -8 -14 -18 -6 -10 -14 -3 -3 -3 1 0 0 0 -24 -11 -7 -10 -13 -11 -3 -9 -5 -7 -7 -5 -7 -8 -6 -7
-24 -9 -12 -14 -11 -9 -8 -14 -14 -16 -12
-21 -20 -20 -15 -19 -18 -16 -21 -21 -19 -19
-6 -10 -12 -7 -9 -11 -10 -12 -10 -11 -10
-14 -19 -21 -13 -16 -20 -19 -22 -18 -18 -19
-21 -27 -28 -18 -24 -30 -30 -28 -24 -25 -27
Final version
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Vlissingen Terneuzen Hansweert Bath Scheldt estuary Liefkenshoek Kallo Antwerpen AVERAGE OS11 OS04 OS14 Netherlands BG2 Haringvliet10 AVERAGE ALL
1.01 1.01 1.00 0.97 0.96 0.96 0.94 0.98 0.99 0.99 0.99 1.00 1.00 0.99 1.00
2.02 2.02 1.97 2.01 1.98 1.96 1.94 1.99 2.00 2.00 1.99 2.00 2.01 2.00 2.00
3.05 3.03 3.06 3.05 3.04 3.04 3.02 3.04 3.02 3.04 3.02 3.03 3.03 3.03 3.02
0.96 0.94 0.93 0.92 0.92 0.92 0.91 0.93 0.97 0.97 0.98 0.97 0.97 0.96 0.97
1.94 1.91 1.89 1.87 1.87 1.87 1.87 1.89 1.94 1.93 1.95 1.94 1.94 1.93 1.96
2.92 2.89 2.87 2.84 2.84 2.84 2.84 2.86 2.92 2.90 2.92 2.91 2.92 2.90 2.95
-10 -9 -13 -11 -13 -13 -15 -12 -8 -7 -9 -10 -13 -10 -8
-19 -22 -21 -20 -20 -19 -17 -20 -14 -10 -15 -14 -21 -16 -15
-28 -31 -23 -33 -34 -35 -38 -32 -19 -10 -18 -21 -29 -22 -21
-14 -16 -15 -17 -19 -19 -20 -17 -12 -14 -15 -10 -11 -13 -10
-24 -28 -29 -33 -35 -36 -37 -32 -20 -23 -24 -20 -22 -23 -18
-29 -34 -35 -41 -44 -45 -49 -40 -27 -32 -33 -29 -27 -31 -25
4.3 Harmonic Analysis of Water Levels Table 5 presents the changes of M2, S2 and M4 tidal amplitude and phase due to SLR of 1, 2 and 3 m. The corresponding plots are shown in Figure 12 to Figure 17. The M2 amplitude is not much influenced by SLR along the French coast. Along the British coast, M2 amplitude increases on average by 2-3 cm. Along the Belgian coast, the M2 amplitude increases proportionally to SLR. For instance, the M2 amplitude is increased by 2 cm, 4 cm and 6 cm with SLR of 1 m, 2 m and 3 m. The M2 tidal phase generally decreases proportionally with SLR. This corresponds to the speeding-up of the tidal wave propagation that was also mentioned in §4.2. The changes are amplified from the British-French coast to the Belgian and Dutch coast. It is more pronounced in the Western Scheldt ( -7, -12 and -18 degrees with SLR of 1 m, 2 m and 3 m). The S2 tidal amplitude is slightly increased in the North Sea by 1 cm, 2 cm and 3 cm with SLR of 1 m, 2 m and 3 m. The effect is slightly larger in the Scheldt estuary (2 cm, 4 cm and 6 cm respectively). The S2 tidal phase decreases in line with the observed effects on M2 tidal phase (e.g. -5, -10 and -15 degree along the Belgian coast). M4 is not the dominant tidal component in the North Sea. The M4 amplitude is slightly changed with SLR. The M4 tidal phase decreases in line with the observed effects on M2 tidal phase (e.g. -7, -14 and -21 degree along the Belgian coast).
Final version
WL2020R19_058_2
15
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Table 5 – Changes of M2, S2 and M4 tidal amplitude and phase due to SLR as observed in ZUNOv4. M2 Amplitude [m]
FRANCE
Belgium
WES
Netherla nds
16
S2 Amplitude [m]
S2 Phase [deg]
M4 Amplitude [m]
M4 Phase [deg]
SLR2
SLR3
SLR1
SLR2
SLR3
SLR1
SLR2
SLR3
SLR1
SLR2
SLR3
SLR1
SLR2
SLR3
SLR1
SLR2
SLR3
Leith
0.00
-0.01
-0.01
-1
-2
-2
0.00
0.00
-0.01
-1
-3
-4
0.01
0.02
0.03
-59
-94
-119
North Shields
0.01
0.01
0.01
-1
-2
-3
0.00
0.00
0.00
-1
-3
-5
0.01
0.02
0.01
2
-5
-14
Whitby
0.01
0.01
0.01
-1
-3
-4
0.00
0.00
0.00
-2
-4
-6
0.00
0.00
-0.01
2
1
-2
-0.03
-0.06
-0.08
-3
-5
-8
-0.01
-0.01
-0.01
-4
-8
-13
-0.02
-0.04
-0.07
-11
-6
0
Cromer
0.00
-0.02
-0.04
-3
-6
-8
0.00
0.01
0.00
-4
-8
-12
0.00
0.01
0.01
3
1
-5
Lowestoft
0.02
0.04
0.06
-2
-4
-5
0.00
0.01
0.01
-3
-7
-10
0.00
0.00
-0.01
-2
-6
-11
Harwich
0.05
0.08
0.12
-5
-10
-14
0.02
0.03
0.04
-5
-10
-16
-0.01
-0.01
-0.01
-24
-42
-60
Sheerness
0.04
0.05
0.05
-8
-15
-22
0.02
0.03
0.03
-9
-18
-26
0.06
0.11
0.13
-35
-59
-79
Dover
0.02
0.04
0.06
-4
-7
-10
0.02
0.03
0.04
-4
-8
-12
-0.01
-0.02
-0.02
-8
-14
-20
Newhaven
0.03
0.05
0.07
-3
-5
-7
0.02
0.05
0.07
-3
-6
-10
0.00
0.00
0.00
-11
-21
-30
Portsmouth
0.04
0.08
0.12
-3
-6
-8
0.03
0.05
0.08
-4
-7
-11
0.00
0.00
-0.01
-13
-26
-36
AVERAGE
0.02
0.03
0.03
-3
-6
-8
0.01
0.02
0.02
-4
-7
-11
0.00
0.01
0.01
-14
-25
-34
CHERBOURG
-0.03
-0.07
-0.11
-1
-1
-1
0.00
-0.01
-0.01
-1
-2
-2
0.01
0.01
0.01
-6
-13
-19
LEHAVRE
0.00
0.00
-0.01
-2
-3
-5
0.02
0.04
0.05
-2
-4
-6
-0.01
-0.01
-0.02
-5
-10
-15
BOULOGNE-
0.01
0.01
0.01
-3
-6
-9
0.02
0.04
0.05
-4
-7
-11
-0.01
-0.02
-0.02
-8
-16
-23
CALAIS
0.01
0.02
0.02
-4
-7
-10
0.01
0.03
0.04
-4
-8
-12
-0.01
-0.01
-0.02
-7
-13
-19
DUNKERQUE
0.01
0.01
0.02
-4
-8
-12
0.01
0.02
0.03
-4
-9
-13
-0.01
-0.01
-0.01
-7
-12
-18
AVERAGE
0.00
-0.01
-0.01
-3
-5
-7
0.01
0.02
0.03
-3
-6
-9
0.00
-0.01
-0.01
-7
-13
-19
Westhinder
0.02
0.03
0.05
-5
-9
-13
0.01
0.02
0.03
-4
-9
-14
0.00
0.00
0.00
-8
-14
-22
Nieuwpoort
0.02
0.03
0.05
-4
-9
-13
0.01
0.03
0.03
-4
-9
-14
-0.01
-0.01
-0.01
-7
-13
-21
Oostende
0.02
0.03
0.05
-5
-9
-13
0.01
0.02
0.03
-4
-9
-14
-0.01
-0.01
0.00
-7
-13
-21
Cadzand Vlakte van de R Westkapelle
0.02
0.04
0.06
-6
-11
-16
0.01
0.03
0.03
-5
-11
-16
0.00
0.00
0.01
-5
-12
-21
0.02
0.04
0.06
-5
-10
-15
0.01
0.02
0.03
-5
-10
-15
0.00
0.00
0.00
-6
-13
-23
0.03
0.05
0.08
-5
-11
-15
0.02
0.03
0.04
-5
-11
-16
0.00
0.00
0.00
-8
-16
-25
AVERAGE
0.02
0.04
0.06
-5
-10
-14
0.01
0.02
0.03
-5
-10
-15
0.00
0.00
0.00
-7
-14
-22
Vlissingen
0.02
0.04
0.07
-6
-11
-16
0.02
0.03
0.04
-6
-12
-17
0.00
0.01
0.01
-4
-12
-21
Terneuzen
0.03
0.06
0.09
-6
-12
-18
0.02
0.03
0.05
-6
-12
-19
-0.01
-0.01
0.00
-2
-11
-22
Hansweert
0.03
0.06
0.10
-6
-12
-17
0.02
0.04
0.05
-6
-12
-18
-0.01
-0.02
-0.01
1
-5
-21
Bath
0.03
0.06
0.10
-7
-13
-19
0.02
0.04
0.05
-6
-13
-20
-0.03
-0.04
-0.04
7
14
-5
Liefkenshoek
0.04
0.07
0.11
-7
-13
-19
0.02
0.04
0.05
-7
-13
-20
-0.03
-0.04
-0.04
9
20
3
Kallo
0.04
0.07
0.11
-7
-13
-19
0.02
0.04
0.05
-7
-13
-20
-0.04
-0.05
-0.04
8
23
7
Antwerpen
0.04
0.07
0.11
-7
-14
-20
0.02
0.04
0.05
-7
-14
-21
-0.04
-0.05
-0.04
-3
12
8
AVERAGE
0.03
0.06
0.10
-7
-12
-18
0.02
0.04
0.05
-6
-13
-19
-0.02
-0.03
-0.02
2
6
-7
OS11
0.02
0.04
0.06
-5
-11
-16
0.01
0.02
0.03
-5
-10
-15
0.00
0.00
0.01
-6
-14
-23
OS04
0.02
0.05
0.08
-6
-12
-17
0.01
0.03
0.04
-6
-11
-17
0.01
0.02
0.03
-6
-13
-22
OS14
0.01
0.03
0.06
-6
-11
-17
0.01
0.02
0.03
-6
-11
-16
0.01
0.01
0.01
-6
-14
-24
BG2
0.02
0.04
0.06
-5
-11
-16
0.01
0.02
0.03
-5
-10
-15
0.00
0.00
0.01
-7
-16
-25
Haringvliet10
0.02
0.03
0.06
-6
-11
-17
0.01
0.02
0.03
-5
-11
-16
0.00
0.01
0.01
-9
-17
-28
AVERAGE
0.02
0.04
0.07
-6
-11
-17
0.01
0.02
0.03
-5
-11
-16
0.00
0.00
0.01
-5
-11
-22
ALL
0.02
0.03
0.05
-4
-9
-13
0.01
0.02
0.03
-5
-9
-14
0.00
0.00
0.00
-7
-13
-23
Immingham
UK
M2 Phase [deg]
SLR1
WL2020R19_058_2
Final version
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 12 – M2 amplitude with SLR as observed in ZUNOv4.
Figure 13 – M2 phase with SLR as observed in ZUNOv4.
Final version
WL2020R19_058_2
17
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 14 – S2 amplitude with SLR as observed in ZUNOv4.
Figure 15 – S2 phase with SLR as observed in ZUNOv4.
18
WL2020R19_058_2
Final version
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 16 – M4 amplitude with SLR as observed in ZUNOv4.
Figure 17 – M4 phase with SLR as observed in ZUNOv4.
Final version
WL2020R19_058_2
19
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary
5 Effect of SLR in the Scheldt estuary The influence of SLR on the Scheldt Estuary is further evaluated in this chapter, based on modelling results from SCALDIS. The tidal propagation is modelled more accurately in SCALDIS than in ZUNO. The time series of water level at measurement stations throughout the Scheldt are analyzed both in the time domain (bias of high/low water) and frequency domain (harmonic components). The influence of SLR on tidal asymmetry in the Scheldt estuary is discussed as well.
5.1 Water level timeseries Figure 18 to Figure 21 illustrate the effect of SLR on levels and timing of high and low water. The statistics are presented in Table 6. In the Western Scheldt, the changes on high water level are generally in proportion to the SLR of 1m, 2m and 3m. However the high water level drops from Lower Sea Scheldt to Upper Sea Scheldt, mainly because the FCA’s are drowned with SLR. At Wetteren and Melle, the high water level are increased even more than the associated SLR. The increase of low water level are generally less than the associated SLR. This is more pronounced from downstream to upstream. In general the low water propagate faster with SLR. This is more pronounced from downstream to upstream. The changes of low water time become less stronger with SLR 3m. In general the high water propagate faster with SLR except near Hansweert. The high water time is even delayed with SLR of 3 m, compared with SLR of 2m. The high water propagate much faster in the Lower Sea Scheldt with SLR of 3m. The different patterns of high and low water time imply a complex pattern of tidal asymmetry along the Scheldt.
20
WL2020R19_058_2
Final version
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 18 – Response of high water level to SLR.
Figure 19 – Response of low water level to SLR.
Final version
WL2020R19_058_2
21
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 20 – Response of high water time to SLR.
Figure 21 – Response of low water time to SLR.
22
WL2020R19_058_2
Final version
Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Table 6 – Bias of high-low water and high-low water time with SLR (SCALDIS). High Water Level [m]
Low Water Level [m]
High Water Level Time [min] Low Water Level Time [min]
SLR1m SLR2m SLR3m SLR1m SLR2m SLR3m SLR1m
SLR2m
SLR3m
SLR1m
SLR2m
SLR3m
Vlakte van de Raan
0.99
2.02
3.05
0.97
1.95
2.92
-6
-15
-22
-10
-18
-24
Westkapelle
1.00
2.02
3.04
0.96
1.93
2.90
-7
-15
-18
-12
-21
-27
Cadzand
0.98
2.01
3.04
0.96
1.96
2.92
-8
-16
-23
-14
-23
-29
Vlissingen
1.01
2.03
3.05
0.96
1.95
2.92
-10
-18
-27
-13
-25
-30
Breskens
1.00
2.02
3.04
0.96
1.95
2.92
-9
-18
-26
-14
-26
-32
Borssele
1.00
2.04
3.04
0.96
1.95
2.92
-9
-23
-34
-14
-24
-30
Terneuzen
1.01
2.03
3.02
0.94
1.93
2.90
-11
-24
-34
-16
-28
-34
Overloop Hansweert
1.02
2.01
3.02
0.94
1.91
2.89
-15
-32
-15
-16
-28
-35
Hansweert
1.02
1.99
3.04
0.93
1.91
2.88
-14
-32
-10
-15
-28
-35
Walsoorden
0.99
1.95
3.07
0.92
1.90
2.87
-17
-16
-22
-17
-30
-37
Baalhoek
0.98
1.99
3.11
0.90
1.86
2.84
-14
-19
-32
-18
-31
-38
Bath
0.94
1.97
3.07
0.92
1.88
2.85
-10
-18
-37
-18
-33
-40
Prosperpolder
0.90
1.97
3.04
0.91
1.87
2.86
-6
-20
-40
-17
-31
-40
Zandvliet
0.92
1.97
3.02
0.92
1.88
2.86
-11
-20
-36
-18
-34
-42
Liefkenshoek
0.91
1.95
2.99
0.91
1.88
2.86
-14
-19
-43
-19
-33
-42
Kallo
0.90
1.93
2.92
0.91
1.88
2.87
-13
-18
-44
-19
-35
-42
Antwerpen
0.90
1.87
2.72
0.91
1.88
2.86
-17
-22
-36
-20
-37
-46
Hemiksem
0.89
1.72
2.75
0.92
1.90
2.89
-17
-14
-22
-20
-37
-47
Boom
0.89
1.75
2.74
0.87
1.82
2.78
-12
-14
-26
-22
-40
-52
Temse
0.86
1.69
2.70
0.89
1.85
2.82
-14
-9
-20
-21
-38
-49
Walem
0.93
1.76
2.75
0.81
1.73
2.65
-13
-23
-24
-24
-44
-59
StAmands
0.84
1.66
2.62
0.82
1.75
2.70
-11
-8
-16
-24
-44
-57
Dendermonde
0.93
1.76
2.66
0.85
1.79
2.74
-7
-16
-15
-26
-45
-59
Schoonaarde
1.03
1.88
2.86
0.78
1.67
2.59
-7
6
0
-28
-49
-66
Wetteren
1.16
2.20
3.22
0.75
1.62
2.54
-9
-3
-18
-34
-56
-76
Melle
1.14
2.23
3.28
0.72
1.58
2.49
-14
-10
-28
-37
-63
-86
Average
0.97
1.94
2.96
0.90
1.85
2.82
-11
-17
-26
-19
-35
-44
5.2 Harmonic analysis of water levels Table 7 present the changes of M2, S2 and M4 tidal amplitude and phase due to SLR of 1, 2 and 3 m respectively. The corresponding plots are Figure 22 to Figure 27. In the Western Scheldt, the M2 amplitude increases proportionally to the SLR of 1m, 2m and 3m. Further upstream the pattern becomes more complex. M2 phase decreases proportionally to the SLR of 1m, 2m and 3m (corresponding to a speeding-up of tidal wave propagation). The decrease is stronger in the upstream. The effect on S2 amplitude gradually increases from downstream to upstream (e.g. from 1 cm downstream to 5 cm upstream). The changes are generally in proportion to SLR in the Western Scheldt. Further upstream the effect on S2 amplitude in scenarios SLR 2m and SLR 3m is basically the same. S2 phase decreases proportionally to the SLR of 1m, 2m and 3m. The decrease is stronger in the upstream. The M4 amplitude gradually decreases from downstream to upstream. The decrease of M4 amplitude is more pronounced with SLR of 2 m, compared with SLR of 1 m and 3 m. The effect on M4 phase is non-monotonous and shows complex features, especially in the Upper Sea Scheldt. This might be related to the influence of FCA’s that will have a stronger impact in the higher SLR scenarios.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Table 7 – Effect on M2, S2 and M4 tidal amplitude and phase due to SLR (SCALDIS).
M2 Amplitude [m] SLR1 SLR2 SLR3 m m m
M2 Phase [deg]
S2 Amplitude [m]
S2 Phase [deg]
M4 Amplitude [m]
M4 Phase [deg]
SLR1 SLR2 SLR3 SLR1 SLR2 SLR3 SLR1 SLR2 SLR3 SLR1 SLR2 SLR3 SLR1 SLR2 SLR3 m m m m m m m m m m m m m m m
Vlakte van de Raan
0.01
0.03
0.04
-5
-10
-15
0.01
0.01
0.02
-4
-8
-13
0.00
-0.01
-0.01
-4
-11
-19
Westkapelle
0.02
0.05
0.07
-5
-10
-15
0.01
0.02
0.03
-4
-9
-13
0.00
0.00
0.00
-5
-13
-22
Cadzand
0.02
0.03
0.05
-6
-11
-16
0.01
0.02
0.02
-5
-10
-15
0.00
0.00
0.00
-2
-7
-15
Vlissingen
0.02
0.04
0.06
-6
-11
-17
0.01
0.02
0.03
-5
-10
-15
0.00
0.01
0.02
-3
-10
-19
Breskens
0.02
0.04
0.06
-6
-12
-17
0.01
0.02
0.03
-5
-11
-16
0.00
0.01
0.02
-3
-9
-17
Borssele
0.02
0.04
0.06
-6
-12
-17
0.01
0.02
0.03
-5
-10
-16
0.00
0.00
0.01
-5
-14
-23
Terneuzen
0.03
0.05
0.08
-6
-12
-18
0.02
0.03
0.04
-5
-11
-17
0.00
0.00
0.01
-4
-12
-21
Overloop Hansweert
0.03
0.05
0.07
-7
-13
-19
0.02
0.03
0.04
-6
-12
-18
-0.01
-0.01
0.01
-6
-17
-29
Hansweert
0.03
0.05
0.08
-7
-13
-19
0.02
0.04
0.05
-5
-11
-18
-0.01
-0.02
-0.01
-5
-15
-28
Walsoorden
0.03
0.05
0.06
-7
-13
-19
0.02
0.03
0.04
-5
-11
-18
-0.02
-0.03
-0.01
-1
-9
-24
Baalhoek
0.04
0.06
0.08
-7
-13
-19
0.02
0.04
0.05
-5
-12
-18
-0.03
-0.04
-0.03
-1
-8
-25
Bath
0.03
0.04
0.06
-7
-13
-20
0.02
0.04
0.05
-5
-12
-18
-0.03
-0.05
-0.04
-1
-5
-23
Prosperpolder
0.03
0.04
0.05
-7
-13
-20
0.02
0.04
0.04
-5
-12
-19
-0.04
-0.05
-0.04
1
6
-13
Zandvliet
0.03
0.04
0.05
-7
-14
-20
0.02
0.04
0.04
-5
-12
-19
-0.03
-0.05
-0.04
-1
-1
-17
Liefkenshoek
0.03
0.04
0.05
-7
-14
-20
0.02
0.04
0.04
-6
-12
-19
-0.04
-0.06
-0.05
-2
1
-12
Kallo
0.03
0.04
0.04
-7
-14
-20
0.02
0.04
0.04
-5
-12
-19
-0.04
-0.07
-0.06
-3
1
-11
Antwerpen
0.03
0.03
0.02
-8
-14
-20
0.02
0.04
0.04
-6
-12
-18
-0.04
-0.09
-0.09
-6
7
42
Hemiksem
0.03
0.01 -0.01
-8
-13
-18
0.02
0.03
0.03
-5
-10
-15
-0.05
-0.11
-0.06
-15
150
116
Boom
0.04
0.03
0.01
-9
-15
-19
0.03
0.04
0.04
-6
-11
-16
-0.04
-0.11
-0.10
-25
-91
-184
Temse
0.04
0.02 -0.02
-8
-14
-18
0.03
0.04
0.03
-6
-10
-14
-0.05
-0.13
-0.08
-22
-118
155
Walem
0.07
0.08
0.07
-10
-16
-20
0.04
0.06
0.06
-7
-12
-17
-0.04
-0.12
-0.12
-28
-79
-162
StAmands
0.07
0.07
0.03
-9
-15
-19
0.04
0.05
0.05
-6
-10
-15
-0.07
-0.17
-0.15
-23
-83
-194
Dendermonde
0.08
0.07 -0.01
-9
-13
-15
0.04
0.04
0.03
-6
-7
-11
-0.06
-0.13
-0.12
-21
-82
-133
Schoonaarde
0.12
0.14
0.09
-11
-14
-15
0.04
0.06
0.05
-6
-6
-8
-0.04
-0.14
-0.13
-23
-95
-170
Wetteren
0.16
0.23
0.21
-12
-18
-23
0.05
0.07
0.07
-8
-11
-18
-0.03
-0.11
-0.15
-29
-64
-85
Melle
0.18
0.26
0.25
-14
-21
-28
0.05
0.08
0.08
-9
-14
-23
-0.03
-0.11
-0.12
-31
-63
-76
Average
0.05
0.06
0.06
-8
-13
-19
0.03
0.04
0.04
-6
-11
-16
-0.03
-0.06
-0.05
-10
-24
-39
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 22 – M2 amplitude with SLR.
Figure 23 – M2 phase with SLR.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 24 – S2 amplitude with SLR.
Figure 25 – S2 phase with SLR.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 26 – M4 amplitude with SLR.
Figure 27 – M4 phase with SLR.
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5.3 Analysis of tidal asymmetry The tidal asymmetries (Friedrichs, 2011) are determined based on local (point) variations of velocity and water level along the thalweg (Figure 28). Based on the different tidal duration, 4 asymmetry parameters are used to analyze and to evaluate the effects of SLR. Ratios larger than one are interpreted as ebb dominance. 1. The tidal asymmetry of the duration of rising and falling phases of the vertical tide. The modeled predicted water levels along the Thalweg (interval of 1 km) are used for analysis. 𝑇𝑇falling 𝑇𝑇rising
Tfalling = time required within the tidal cycle to change water level from HW to LW. Trising = time required within the tidal cycle to change water level from LW to HW; 2. The tidal asymmetry based on duration of ebb and flood (horizontal tide). The modeled crosssectional averaged velocities are used for determine the ebb-period and flood period (see locations in Figure 28). 𝑇𝑇ebb 𝑇𝑇flood
Tebb = duration of ebb flow during the tidal cycle. Tflood = duration of flood flow during the tidal cycle; 3. The tidal asymmetry of the maximum current flow velocities during ebb and flood phases. This tidal asymmetry parameter is based on maximum (cross-sectionally averaged) velocity during flood and during ebb within the tidal cycle. 𝑉𝑉max 𝑒𝑒𝑒𝑒𝑒𝑒 𝑉𝑉max 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
Vmaxebb = maximum current velocity during ebb phase. Vmaxflood = maximum current velocity during flood phase; 4. The tidal asymmetry of the mean (cross-sectionally averaged) flow velocities during ebb and flood phases. 𝑉𝑉mean 𝑒𝑒𝑒𝑒𝑒𝑒 𝑉𝑉mean 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓
Vmeanebb = mean current velocity during ebb phase.
Vmeanflood = mean current velocity during flood phase; Figure 29 presents the duration asymmetry along the thalweg under SLR. For the present situation (SLR = 0m), the Scheldt is at the boundary of being flood and ebb-dominant. Further upstream we see a longer falling than rising tide, which corresponds to ebb dominance. SLR tends to decrease the difference in duration between ebb and flood phase of the tide, and in that sense reduces the ebb dominance upstream of km 100. Figure 30 shows the velocity asymmetry. In general the ratio between maximum velocity during ebb and flood increases with SLR, which is more pronounced in the upstream than downstream. The ratio between mean velocity during ebb and flood show a similar pattern with SLR. In terms of velocities, the Scheldt estuary is expected to become more ebb-dominant with SLR.
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The different results for different definitions of tidal asymmetry does not allow a straightforward interpretation in terms of expected morphological response, and warrants future research, e.g. with a sediment transport model. Figure 28 – Thalweg along the Scheldt in grey (resolution of 1 km). The black lines represent the cross-sections where the averaged velocity (discharge/cross-sectional-area) are computed.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 29 – Duration asymmetry. Top panel: Duration of falling / rising tide. Bottom panel: Duration of ebb / flood.
Figure 30 – Velocity asymmetry. Top: max ebb velocity / max flood velocity. Bottom: mean ebb velocity / mean flood velocity
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5.4 Inundation of Flood Control Areas Figure 31 presents the time series of water level at Antwerp predicted by SCALDIS with SLR of 0 m. The tidal cycle with highest water level (3.75 m NAP) is marked in red. This 12-hour tidal cycle starts from 01-Sep-2015 12:20:00 to 02-Sep-2015 00:20:00. The maximum water depth at each calculation node over this 12-hour tidal cycle are extracted from the model and used to illustrate the Inundation of Flood Control Areas (see Figure 32 to Figure 43). Figure 31 – Time series of water level predicted by SLR0m at Antwerp. The red line indicates the tidal cycle with the highest water level.
With SLR some of the FCA’s in the Scheldt are drowned which is more noticeable with SLR of 3 m. Figure 33 shows that the Hedwigepolder en Doelpolder are drowned with SLR, the change of depth is more or less in proportion to the SLR of 1 m, 2 m and 3 m. Figure 34 shows that the KBR is drown by more than 3 meters even with SLR of 1 m only. Figure 37 shows that Klein Broek en Groot Broek are not influenced by SLR because they are not activated yet (by setting bathymetry to +6 m NAP in the model). These examples imply that the interactions between FCA’s along the Scheldt and SLR are complex. It will lead to large impact on the results analysis presented in this study. Figure 32 – Depth difference under SLR. The black lines indicate the FCAs.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 33 – Depth difference under SLR. Zoom into FCA of Grensgebied, Hedwigepolder en Doelpolder.
Figure 34 – Depth difference under SLR. Zoom into FCA of Burchtse Weel en KBR.
Figure 35 – Depth difference under SLR. Zoom into FCA of Oudbroekpolder, Schellandpolder, HingeneBroekpolder, Spierbroekpolder, Groot Schoor, Stort Hingene, Stort Ballooi en Schouselbroek.
32
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 36 – Depth difference under SLR. Zoom into FCA of Tielrodebroek, De Bunt, Lippenbroek.
Figure 37 – Depth difference under SLR. Zoom into FCA of Klein Broek en Groot Broek.
Figure 38 – Depth difference under SLR. Zoom into FCA of Potpolder I en Polder van Waasmunster.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 39 – Depth difference under SLR. Zoom into FCA of Potpolder IV.
Figure 40 – Depth difference under SLR. Zoom into FCA of Blankaart, Zwijn, Grote Wal en Kleine Wal, Uiterdijk, Vlassenbroek I en Vlassenbroek II.
Figure 41 – Depth difference under SLR. Zoom into FCA of Scheldebroek, Paardeweide en Bergenmeersen.
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Validation of North Sea models - Sub report 2 – The impact of sea level rise on hydrodynamics: North Sea and Scheldt Estuary Figure 42 – Depth difference under SLR. Zoom into FCA of Wijmeers I en Wijmeers II, Bastenakkers en Ham.
Figure 43 – Depth difference under SLR. Zoom into FCA of Zandput Melle en Heusden.
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6 Conclusions The influence of SLR on the tidal characteristics in the North Sea and in the Scheldt estuary is evaluated in a scenario analysis for three scenarios of SLR: 1 m, 2 m and 3 m respectively. DCSMv6-ZUNOv4 and SCALDIS are selected as the modelling instruments to run for 2 spring-neap cycles in 2015 without wind and pressure forcing (purely harmonic run). Note that the SLR of 1 m, 2 m and 3 m is imposed constantly at the boundary of DCSM in this study. In reality the SLR may be non-uniform in space. A better approximation could be obtained by modelling global SLR with a global tide and surge model (not currently present at FHR). In the North Sea, the M2 amplitude increases under SLR in the Southern Bight domain. The southern amphidromic point (closest to the Belgian Coastal Zone - BCZ) moves north-eastwards with SLR of 1 and 2m. In the scenario of SLR of 3m, the amphidromic point shifts to the north-west. The effect on high water generally follows the SLR of 1m, 2m and 3m. The effect on low water generally equals the SLR at the British and French coast. However along the Belgian and Dutch coast, the low water level increases less than SLR. This is consistent with the rise in tidal amplitude with increasing SLR. In general the tidal wave propagates faster with increasing SLR. This is to be expected, as the propagation speed c0 of a tidal wave in deep water is given by the formula: 𝑐𝑐0 = �𝑔𝑔𝑔𝑔
With H the water depth. So the propagation speed of a tidal wave scales with the square root of the water depth. Note that this formula is an approximation, since the North Sea does not qualify as “deep water” for tidal wave propagation. Along the Belgian coast, the effect on the timing of high water is 7, 12 and 19 mins earlier due to SLR of 1, 2 and 3 m. The effect on the low water levels is higher (10, 19 and 27 mins). The difference between both effects indicates an expected change in the shape of the tidal curve due to SLR. Along the Belgian coast, the M2 amplitude increases with 2 cm, 4 cm and 6 cm with SLR of 1 m, 2 m and 3 m. The M2 tidal phase decreases, consistent with the faster propagation of the tidal wave. In the Scheldt Estuary, the changes on high water level are generally in proportion to the SLR of 1m, 2m and 3m. However the high water level drops in the Upper Sea Scheldt, mainly because the FCA’s are presented in the model mesh, and the depoldered areas become drowned with SLR. At Wetteren and Melle on the other hand, the high water level increase more than SLR. The increase of low water levels is less than SLR. This drop in LW is more pronounced upstream, and can be partly explained by the lesser effect of fresh water discharge, relative to the increasing water volume with increasing SLR. Low waters come more quickly under increasing SLR, and the effect is stronger upstream (up to >80min for Melle under 3m SLR). Note that the FCA’s presented in the SCALDIS model are based on the current situation. In the far-future, these FCA’s could be adapted to SLR. These adaptations are not considered in the present study. The tidal asymmetry along the thalweg is evaluated based on tidal duration (falling/rising, ebb/flood) and velocities (maximum and mean) under different SLR scenarios. With SLR the initial effect in the estuary is that it becomes less ebb-dominant in terms of duration asymmetry upstream of km 100 (more equal timing of periods of ebb and flood). But the estuary becomes more ebb-dominant in terms of velocity asymmetry. The different results for different definitions of tidal asymmetry does not allow a straightforward interpretation in terms of expected morphological response, and warrants future research, e.g. with a sediment transport model. Note that the morphological response to SLR is not considered in this study. The redistribution of sediments (erosion/deposition) will certainly modify the hydrodynamics in the estuary which in turn will further change the morphodynamics in a feed-back loop that is difficult to model accurately. Therefore one should note that the effects presented in this study are so-called initial effects. 36
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7 References Chu, K.; Vanlede, J. Decrop, B.; Verwilligen, J.; Mostaert, F. (2017). Update snelheidsvelden Zeeschelde en Sluistoegangen: Technical Report. Version 2.0. FHR Reports, 00_081_1. Flanders Hydraulics Research: Antwerp. IMDC: I/RA/11502/16.179/KCH/. Chu, K.; Vanlede, J.; Decrop, B.; Mostaert, F. (2020). Validation of North Sea models: Sub report 1 – Validation and sensitivity analysis. Version 3.0. FHR Reports, 19_058_1. Flanders Hydraulics Research: Antwerp. IMDC: I/RA/11502/19.122/KCH/ Friedrichs, C.T.; Aubrey, D.G. (1988). Non-linear tidal distortion in shallow well-mixed estuaries: a synthesis. Estuar. Coast. Shelf Sci. 27(5): 521–545. doi:10.1016/0272-7714(88)90082-0. Friedrichs, C. T. (2011). Tidal Flat Morphodynamics: A Synthesis. Virginia Institute of Marine Science: Gloucester Point, VA, USA, 137-170. Muis, S.; Apecechea, M.I.; Haasnoot, M.; Verlaan, M.; de Winter, R. (2019). Assessing global changes in tides due to sea-level rise. Geophysical Research Abstracts. Vol. 21, EGU2019-16246, 2019. Pickering, M.D.; Wells, N.C.; Horsburgh, K.J.; Green, J.A.M. (2012). The impact of future sea-level rise on the European shelf tides. Continental Shelf Research 35, pp. 1-15. Pickering, M.D.; Horsburgh, K.J.; Blundell, J.R.; Hirschi, J.J.M.; Nicholls, R.J.; Verlaan, M.; Wells, N.C. (2017). The impact of future sea-level rise on the global tides. Continental Shelf Research 142, pp. 50-68. Smolders, S.; Maximova, T.; Vanlede, J.; Plancke, Y.; Verwaest, T.; Mostaert, F. (2016). Integraal Plan Bovenzeeschelde: Subreport 1 – SCALDIS: a 3D Hydrodynamic Model for the Scheldt Estuary. Version 5.0. WL Rapporten, 13_131. Flanders Hydraulics Research: Antwerp, Belgium. Speer, P.E.; Aubrey, D.G.; Friedrichs, C.T. (1991). Nonlinear hydrodynamics of shallow tidal inlet/bay systems, in: (1991). Tidal Hydrodynamics. John Wiley & Sons. pp.321–339. Taal, M. (2019). Veranderingen getij NL kust bij zeespiegelstijging. Deltares, Delft, the Netherlands
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Appendix A
Definition of Statistics
Water levels The Bias of water level represents the average deviation of the differences between model predicted water level and measurement. The mathematical expressions are listed below. y and x represent modelled and measured values respectively.
Bias=
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Appendix B SCALDIS
Comparison between ZUNOv4 and
In order to check how well the impact of SLR represented in the models, Table 8 presents a comparison between modelled effects at Vlissingen, both for ZUNOv4 and SCALDIS. Both models show similar statistical results, both in the time domain as in the frequency domain. This result shows that the nesting between both models works well, and that the effect in Vlissingen is qualitatively the same in both models. For the effects further upstream in the estuary, it is advisable to use the results of the Scaldis model there. Table 8 – Results comparison at Vlissingen between ZUNOv4 and SCALDIS.
Vlissingen
High Water Level [m]
Low Water Level [m]
High Water Level Time [min]
Low Water Level Time [min]
M2 Amplitude [m]
M2 Phase [deg]
S2 Amplitude [m]
S2 Phase [deg]
A2
Scenario
ZUNOv4
SCALDIS
SLR1m
1.01
1.01
SLR2m
2.02
2.03
SLR3m
3.05
3.05
SLR1m
0.96
0.96
SLR2m
1.94
1.95
SLR3m
2.92
2.92
SLR1m
-9.6
-10.2
SLR2m
-19.1
-18.1
SLR3m
-27.6
-26.6
SLR1m
-13.9
-13.0
SLR2m
-24.3
-24.8
SLR3m
-29.4
-29.6
SLR1m
0.02
0.02
SLR2m
0.04
0.04
SLR3m
0.07
0.06
SLR1m
-5.90
-5.91
SLR2m
-11.32
-11.38
SLR3m
-16.48
-16.66
SLR1m
0.02
0.01
SLR2m
0.03
0.02
SLR3m
0.04
0.03
SLR1m
-5.76
-4.98
SLR2m
-11.55
-10.12
SLR3m
-17.13
-15.26
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DEPARTMENT MOBILITY & PUBLIC WORKS Flanders hydraulics Research Berchemlei 115, 2140 Antwerp T +32 (0)3 224 60 35 F +32 (0)3 224 60 36 waterbouwkundiglabo@vlaanderen.be www.flandershydraulicsresearch.be