Effect of fresh water discharge on the salinity intrusion in the Scheldt estuary: final Report

This report includes a study of the effect of fresh water discharge in salinity of the river Scheldt. The study consists of a series of simulations with the NEVLA3D model to investigate salinity variation in several upstream discharge conditions.Three scenarios were set up. The reference scenario includes constant discharges at 8 river sources taken as the mean annual discharge for the year 2006. A scenario with doubled discharges (N002) and another one with half reduced discharges (N003) are implemented. Simulations were carried out for a period of three months. Transient effects are investigated by modelling a single-day discharge peak.The results of this study can be used to model sediment transport in DELWAQ, in order to investigate the effect of fresh water inflow on (cohesive) sediment transport, through changes in estuarine circulation

Neumann (water level gradient) boundaries in TELEMAC 2D and their application to wave-current interaction

Water Qualit

Morphodynamic impact of sea-level rise on the Western Scheldt estuary and its mouth region:insights from an idealized modeling study

Estuaries lie at the interface of land and sea, and are particularly vulnerable to sea-level rise (SLR). Understanding the impact of SLR on the long-term (order decades to centuries) morphodynamic evolution of estuaries is of great importance to successfully manage these areas, such as maintaining shipping routes and preserving ecosystems. An analysis of historical water level data at Vlissingen (Figure 1) between 1900 and present revealed that the mean sea level has been rising at about 2 mm/yr. Moreover, these data show that the amplitude of the dominant tidal constituent (M2) has been rising as well during this period (Figure 2), which most likely is caused by the rising mean sea level (Pickering et al. 2012, Idier et al, 2017). The specific aims of this study are 1) to investigate the impact of SLR (2 mm/yr) on long-term evolution of the Western Scheldt and its mouth region, 2) to systematically explore sensitivity of model results to different rates of SLR (0-10 mm/yr), and 3) to address the combined effect of SLR and changes in tidal characteristics on the evolution of the estuary. To this end, the coupled SWAN-Delft3D numerical model is used, which accounts for both flow and waves. A curvilinear grid is created, which extends from Ghent to 30 km seaward. As a wave climate, a highly simplified wave forcing (constant wave height, wave periods and wave direction) is considered. The methodology employed is that first the model is spun-up until a bathymetry is obtained that is comparable to observations. Subsequently, the latter bathymetry is used to address the objectives An important model result is that stronger tidal currents are crucial to prevent sedimentation in channels caused by SLR. This result and other findings will be discussed during the presentation

Least-squares spectral element method applied to the Euler equations

This paper describes the application of the least-squares spectral element method to compressible flow problems. Special attention is paid to the imposition of the weak boundary conditions along curved walls and the influence of the time step on the position and resolution of shocks. The method is described and results are presented for a supersonic flow over a wedge and subsonic, transonic and supersonic flow problems over a bump

Scientific support regarding hydrodynamics and sand transport in the coastal zone: literature and data review coastal zone Zeebrugge - Zwin

In this report the available literature and data relevant for the coastal zone between Zeebrugge and the Zwin is summarised.Since the extension of the harbour of Zeebrugge (finalised in 1986) a lot of bathymetrical data are available. With these data the evolution around Zeebrugge (including the Western part, area around the harbour breakwaters, Baai van Heist, the beaches of Knokke and the Appelzak gully) can be reconstructed. But also before this extension some data are available, such that the difference pre and post extension can be compared.Other data and literature are also described, including numerical modelling of currents and morphology, detailed hydrodynamic and sediment transport measuring campaigns and analysis of the sediment composition.In front of Knokke-Heist the beaches are eroding due to the presence of the Appelzak-gully. The Appelzak shows a long term landward movement. However the movement and development of the gully seems to slow down during the last 10 years. Although confirmation is needed (both based on further trend analysis and numerical modelling), this might suggest that big scale measures to reduce erosion, might be less effective Possibilities for the slow down are the more equilibrium state of the system after the extension of the harbour of Zeebrugge and the influence of the large nourishments in the last decade .Consequently, also the erosion in front of Knokke-Heist is clearly slowing down during the last decade

Scientific support regarding hydrodynamics and sand transport in the coastal zone: calibration of a Long term morphological model of the Belgian shelf

Longshore sediment transport in the surf zone plays a considerable role in the long-term morphological behaviour of the Belgian coast. Based on previous efforts (Zimmermann et al., 2013b; Zimmermann et al., 2013), this report firstly presents a 2D numerical model which covers almost the entire Belgian coast from Nieuwpoort to the Zwin. With the MorMerge online-parallel approach the time horizon for modelling long term morphology in the surf zone was successfully increased to 10 years. Compared with the measurement data, most major morphological changes in the surf zone are well captured qualitatively by the 2D numerical model with an exception of the sedimentation in the Baai van Heist. The modelled sedimentation/erosion is further quantitatively compared with beach accretion/erosion trends of the last 25 years reported in Houthuys (2012). This model still shows a reasonable agreement and its quality is discussed. The sedimentation in the Baai van Heist is specially investigated by an updated 2D and later a new 3D model. For a further validation of the model used in this study, another 3 models OKNO, Zeebrugge and MU-HEIST are introduced and their results are compared with that of the model used in this study. After a series of sensitivity tests a roughness map is employed to update the 2D model, but the updated 2D model seems to be still unable to reproduce the sedimentation in the Baai van Heist properly, especially from the quantitative point of view. To avoid the Gallapatti time scale, a new 3D model is built up, and driven by boundary condition of full spring-neap tides rather than representative ones imposed in the 2D model. With the technique of time-varying MorFac and multiple sediment fractions, the 3D model shows a quite good potential to reproduce the sedimentation in the Baai van Heist. Based on the promising result produced by the 3D model, additional work is proposed for further investigation and research in the future