L. Jiang1*, T. Gerkema1, D. Idier2, A. Slangen1, K. Soetaert1
2 French geological survey (BRGM), France
Sea-level rise (SLR) poses flooding risks to estuaries and coastal bays around the world. SLR not only changes mean water levels but also can modify local tidal dynamics. Understanding the SLR-induced local tidal changes is essential to planning coastal defense activities. Shifts in tidal regimes may modulate the direction and amplitude of sediment transport.
An existing Oosterschelde hydrodynamic model was coupled with a European shelf model (Idier et al., 2017). The latter models water levels and current velocity for 0 m to 2 m SLR scenaios; they were used as a boundary condition to drive the local domain, assuming no coastal flooding.
The simulated water level in the baseline scenario agrees relatively well with observations at tidal gauges. SLR up to 2 m (possibly reached by 2100 or 2200) would submerge all tidal flats in the Oosterchelde and increase the tidal range, high water, and tidal currents, which are more responsive than the adjacent North Sea. With SLR up to 2 m, it is likely that tidal asymmetry (flood dominance) would be reduced, contributing to a decline in landward bedload sediment transport. Turnover time in the Oosterschelde would be mostly shortened with SLR-induced stronger tidal flushing. SLR also alters the local flushing characteristics by modulating the residual current field. Approaches and findings in this study have implications for understanding the local impacts of SLR on the Dutch coast as well as in global estuaries and coastal bays.
Figure 1 Simulated spatially average tidal range in the Oosterschelde in the SLR scenarios. The line denotes the linear regression between the average tidal range and SLR amplitude.