Numerical modeling: The effect of land subsidence on hydrodynamic conditions and coastal morphology in Pekalongan

Abstract

This study examines the effect of land subsidence on hydrodynamic conditions and coastal morphology through numerical modeling using MIKE21 with 30-day simulation time. Land subsidence is assumed to be 10 cm/year, which affects bathymetry. There are 2 modeling scenarios, scenario 1 before (2016) and scenario 2 after land subsidence (2021). River discharge is assumed to be constant at 10 m3/s. The model calibration result on water level elevation and current velocity of the model simulation output and field data comparison based on the variation of Chezy Number, the smallest error was obtained at Chezy Number 50 m0.5/s. The sediment transport model sensitivity test was conducted on parameters of model type, sediment grain size, and river discharge. The result of sensitivity test demonstrated that the sediment grain size is the most sensitive parameter. By comparing the two model scenario results show that the current velocity in scenario 1 is greater than scenario 2 by 20%, significant wave height in scenario 1 is smaller than scenario 2 up to 0.1 m, and sedimentation in Mangrove Park increases up to ± 0.01m. Land subsidence reduces the current velocity, increases the significant wave height and sedimentation.