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

Pushpa Dissanayake, Harshinie Karunarathna, Roshanka Ranasinghe

Friday 3 july 2015

9:45 - 10:00h at Europe 2 (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) Morphodynamics of estuaries and coastal areas

Parallel session: 14I. Extreme events - Lessons Disaster

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 results in 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.