Modification of Dune Erosion by adjacent Coastal Systems (MoDECS)

• Applicant: Dr.-Ing. Pushpa Dissanayake, Ph.D.
• Subject Area: Geotechnics, Hydraulic Engineering ; Oceanography
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 388261860

Coastal beach and dune systems have high economic and environmental values, and provide a natural defence for the hinterland against the marine forcings (tides, waves, sea level rise), particularly during storm events. Commonly beach-dune systems on straight sand plains are taken into account in scientific analyses. However, the presence of adjacent coastal morphological elements (ebb tidal-deltas, inlet channels) changes the marine forcing and modifies dune erosion characteristics. The main objective of this research is to understand the communication between coastal elements and gain insights into the modification of storm erosion processes by investigating three distinct coastal systems: 1) Isolated Dune System (IDS), 2) Barrier-island Dune System (BDS) and 3) Estuarine Dune System (EDS). A novel approach uses a simplified (and therefore generic) representation of the exemplary dune systems from Hütelmoor (IDS), Norderney (BDS) in Germany and Sefton coast (EDS) in UK, located in different energy environments (tidal range, wave height). Numerical experiments using XBeach, Delft3D and SWAN models will be carried out with three schematisations of the dune systems (cross-shore dune profiles, two-dimensional dune areas and a model-based BDS), of which the complexity gradually increases, to simulate the storm erosion processes. In the first year of the project, a morphodynamically relevant storm definition will be initially established for the numerical experiments and used to define the previously occurred storm events at the three dune systems. Then, the cross-shore profiles will be simulated to investigate the erosion sensitivity to the bed topographic parameters like dune slope and dune width. In the second year, the two-dimensional areas will be simulated to investigate the impacts on the storm erosion processes by the morphological elements of inlets and estuarine environments, and the flow and sediment discharges. In the third year, a model-based beach and dune system which has a complex channel and shoal pattern similar to the nature of the BDS will be developed using long period (decadal) simulations. This will then be used to investigate the impacts of two climate change scenarios (sea level rise and storm occurrence) on the storm erosion at dunes surrounded by the morphological elements. Research findings will be disseminated via journal articles (Climatic Change) and conference proceedings.The project duration is 3 years and the host institution is Center for Marine Environmental Sciences (MARUM), University of Bremen. The research will be carried out in close collaboration with the internal and the external researchers (NOC: Liverpool, UNESCO-IHE: Delft, IOW: Warnemünde and CRS: Norderney). Annual meetings will be convened with the relevant experts to discuss findings and to receive feedback.

• DFG Programme: Research Grants