147. Modelling Paleo-Geomorphology of Wave-Dominated Sandy and Tide-Influenced Muddy Coastal Embayments on the Decadal to Centennial Scale: A Comparative Study

In front of the modern changing climate, an integrated coastal zone management requires future scenarios of coastal evolution that can be projected by multi-scale Long Term Morphodynamic Models (LTMMs). A realistic initial Digital Elevation Model (DEM) assigned to the historical starting time is essential for calibrating and validating these models. By using the information of historical coastline changes, relative sea level record and modern DEM, the inverse modelling method (i.e. Dynamic Equilibrium Shore Model, DES Model) has been developed and validated for approximately estimating historical morphology at the Pomeranian Bay, southern Baltic Sea. This model bears also the potential for future projection of coastal morphogenesis based on sea level rise scenarios. The Pomeranian Bay is a wave-dominated sandy coast where sand remains within the coastal area and fine-grained suspended matter discharged by rivers is transported cross-shore basinward. A Long-shore Sediment Transport Capacity Model (LSTC) has proven the area to be semi-enclosed – one of the main preconditions for applying the inverse model to coastal environments. For comparison the Laizhou Bay (Bohai Sea) has been selected as a research area. Here, joint factors such as river discharge, tides, waves, and sea level variations shape the nearshore bottom morphology. In addition to the wind-wave driven Long-shore Sediment Transport Capacity, tidal residual currents are also important for estimating long-shore sediment flux to determine the boundary of the semi-enclosed area. At the Laizhou Bay, the muddy sediments at the sea bottom descend from numerous rivers’ discharges. So, the riverine sediment source has to be taken into account here when balancing the sediment mass as distinguished from the Pomeranian Bay. In terms of modelling coastal morphogenesis, the comparative study carried out here helps to understand different formation mechanisms of wave-dominated sandy coast and tide-influenced muddy coast.