Numerical Modelling of Coastal Erosion using MIKE21

Abstract

Coastal erosion is a problem that is increasingly being faced world over. This erosion is important not only in tropical areas but also in the Arctic region. Many numerical models exist today to predict coastal erosion at a given site. There has not been much progress in modelling erosion due to waves in combination with thermo-mechanical erosion occurring in the Arctic coasts. SAMCoT (Sustainable Arctic and Marine Coastal Technology) at NTNU (Norwegian University of Science and Technology, Trondheim) has initiated research in Baydara Bay, Russia to analyse and study the erosion occurring at the site and to arrive at an understanding of the processes involved. A site on the Ural coast of the bay has been selected for the surveys and is the location studied for this research.The research carried out in this thesis aims to create a model to represent the hydrodynamics and sediment transport patterns prevalent at the site using MIKE21 developed by DHI. MIKE21 is a comprehensive coastal modelling suite which simulates hydrodynamics, wave field, sand transport, mud transport and advection-diffusion of environmental pollutants. As the research is in its initial stages, the data from the site for calibration is not available at this point of time. Calibration has been attempted based on the current data provided by Dr. S. Ogorodov (Senior researcher, Moscow State University) collected in August 2006. The model results were found to be in good agreement with this collected data. The results show a high bed resistance value which is attributed to the vegetation and presence of permafrost in the sediment layer.Using the results, the hydrodynamic conditions for a more recent time frame are presented for which the sediment transport pattern is also predicted. Absence of sufficient field data has guided the research to provide a sensitivity analysis of sediment transport at the site of interest. The idea behind this is to provide a starting point for further research that can be continued based on the results obtained in this study. A sensitivity analysis of the sediment transport is presented for the following parameters:? Grain size diameter? Importance of waves? Importance of model formulationsThe sensitivity analysis shows that the waves are of primary importance compared to tidal currents. The sensitivity of results to variation in sediment grain size are also discussed. In conclusion, limitations of the model and scope of future research are outlined.