Abstract
Episodic coastal hazards associated to sea storms are responsible for sudden and intense changes in coastal morphology. Climate change and local anthropogenic activities such as river regulation and urban growth are raising risk levels in coastal hotspots, like low-lying areas of river deltas. This urges to revise present management strategies to guarantee their future sustainability, demanding a detailed diagnostic of the hazard evolution. In this paper, flooding and erosion under current and future conditions have been assessed at local scale at the urban area of Riumar, a touristic enclave placed at the Ebro Delta (Spain). Process-based models have been used to address the interaction between beach morphology and storm waves, as well as the influence of coastal environment complexity. Storm waves have been propagated with SWAN wave model and have provided the forcings for XBeach, a 2DH hydro-morphodynamic model. Results show that future trends in sea level rise and wave forcing produce non-linear variations of the flooded area and the volume of mobilized sediment resulting from marine storms. In particular, the balance between flooding and sediment transport will shift depending on the relative sea level. Wave induced flooding and long-shore sand transport seem to be diminished in the future, whereas static sea level flooding and cross-shore sediment transport are exacerbated. Therefore, the characterization of tipping points in the coastal response can help to develop robust and adaptive plans to manage climate change impact in sandy wave dominated coasts with a low-lying hinterland and a complex shoreline morphology.
Highlights
Population growth and migration from rural to urban areas will lead low-elevation coastal zones or LECZ to held a higher population density and a greater rate of urbanized land in the incoming years, a worldwide phenomenon especially critical in developing countries of Asia and Africa [1,2]
The emerged beach width is reduced along the whole coastline due to wave impact, the barrier dunedune remains in allremains cases, except most energetic events
The relative relative contribution contribution to total flooding associated to waves and sea level, indicates how the the coastal geomorphology interacts with episodic flooding hazard
Summary
Population growth and migration from rural to urban areas will lead low-elevation coastal zones or LECZ (i.e., contiguous area to the sea at less than 10 m height) to held a higher population density and a greater rate of urbanized land in the incoming years, a worldwide phenomenon especially critical in developing countries of Asia and Africa [1,2]. Global warming may strongly modify the hydrodynamic forcings that drive flooding and erosion: sea level and wave climate In this way, the 5th Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) [10] estimates the global sea level rise (SLR) at the year 2100 to range between 0.52 and 0.98 m with respect to the 1986–2005 period, for the highest emission RCP 8.5 scenario. According to Church et al [10], sea level rise has a 33% probability to lie outside this 5% to 95% confidence interval, being the main source of uncertainty the collapse of the Antarctica ice sheet areas In this regard, Jevrejeva et al [11] propose an upper limit or worst-case projection for the global sea level rise of 1.80 m by 2100, considering the high-end estimations of each sea level rise contributor for the RCP 8.5 scenario. This estimation would have a 5% probability of being exceeded
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