Author(s): Ronja Ehlers; Weizhi Wang; Arun Kamath; Hans Bihs
Linked Author(s): Hans Bihs
Keywords: No Keywords
Abstract: Coastlines are exposed to external loads from the seaside e. g., due to impact from wind, waves and current. Storm events can result in severe erosion and affect the stability of the slope and coastal structures which eventually provokes a failure scenario and puts coastal structures at risk. The IPCC has identified the following coastal climate impact-drivers that are projected to increase in almost all reference regions: relative sea level, coastal flood and coastal erosion, where the response to ocean warming as a rise in sea level is expected to hold over decades or even centuries (IPCC, 2021). With an increase in wave energy and wave action, coastal zones need to be aware of possible impacts (Griggs & Reguero, 2021; Reguero et al., 2019; Taherkhani et al., 2020). Vertical, impermeable seawalls pose a risk for erosion at the toe of the structure but also in the crossshore profile of the sediment bed further away from the structure. These highly reflective structures are mainly early approaches built with the purpose of sea defense but are not considered state-of-the art for coastal protection nowadays where more advantageous shapes or partly permeable types are favored. However, the study of the sediment transport processes associated with an artificial reflecting structure such as a seawall in contrast to the natural surf and swash zone can provide insight into the involved mechanisms and dominating factors. Moreover, this study evaluates a Shallow-Water-Equations (SWE) model with a non-hydrostatic pressure assumption for sediment transport modeling at the coastline while comparing it to results from a 3D Computational Fluid Dynamics (CFD) model. The case chosen in this study, a vertical seawall approached by irregular waves with experimental data from Fowler (1992), describes cross-shore sediment transport in a 2D scour scenario. The results are evaluated with focus on the initial and developing interaction between wave, sediment bed and structure, including the breaking point, wave run-up and resulting shear stresses leading to the erosive process.
Year: 2022