Numerical modelling of land subsidence effect on coastal sediment transport in Pekalongan

Abstract

This study examines the condition of sediment transport on the Pekalongan coast by a numerical model computation using the Delft3D Flow module. The research was started by collecting and analysing field data both primary and secondary. Thus, the hydrodynamic and sediment transport model are then calculated in two scenarios which are representing the conditions before (2016) and after (2021) land subsidence by assuming a land subsidence of 10 cm/year. The numerical model is then calibrated and verified on the data of tidal water level elevation and current velocity, the best results are obtained at a chezy number of 60 m0.5/s, and sensitivity tests are carried out on changes in sediment grain size, wave height and wave direction in order to determine the characteristics of the numerical model. The sensitivity analysis of sediment grain size is the most sensitive effect to sediment transport characteristic. The results of the numerical model are then compared based on the scenarios before (2016) and after the occurrence of land subsidence (2021). The results indicate that after land subsidence, the sedimentation rate is increasing by 56.34%, whereas the erosion rate is decreasing by 3.98% after one neap-spring tidal cycle (around 15 days) in the study area.