Numerical Simulation of Hydrodynamic for Abrupt Bathymetry in Palu River Estuary

The failure of numerical simulation for hydrodynamic model in abrupt bathymetry zone is one of the obstacles in solving environmental problems in coastal zone. The research aims to make three dimensional hydrodynamic model in Palu river estuary that has abrubt bathymetry using ECOMSED. The simulation was conducted on horizontal and vertical cross section with the boundary condition of model, i.e. the depth data was used at the bottom of the river and the sea, river discharge at upstream and tide constituents at downstream. Input data and interpolation program was made in solving error problem. Run time error occurred during simulation, therefore, experimental method was used by modifying input data and increasing the number of grid and time step resolution to make calculation became stable. The results revealed that the influence of tidal current in Palu river estuary is smaller than the influence of river discharge and the temperature is mainly distributed westward on the horizontal cross section. While on the vertical cross section, the direction of temperature distribution follows the current movement pattern based on the overlay between current and temperature distribution. The calculated surface elevation and current velocity on the vertical cross section well suits with the secondary data obtained from hydro oceanographic office and observed current velocity.