Development of a two‐dimensional finite element model for inundation processes in the Tonle Sap and its environs

A hydrodynamic model, which covers the floodplains of the Mekong River from Kratie in Cambodia to near the Vietnamese border, was developed using a finite element method (FEM) with 2D shallow‐water equations. The model was applied to typical flows of recent largest (2000) and smallest (2003) flood years. Main roads, dikes, colmatages, and road‐opening works in the study area, which may influence flow regimes, were introduced into the simulation. Moving boundary problems were accommodated by applying a threshold technique in which nodes having a thin water depth were reset to dry ones in all moving boundary elements at every time increment. Simulated results and available observed water levels and discharges were compared to validate the model. The simulated results produced a lot of hydrologic data for the basin areas, without gauging, and these data can be used to evaluate the effects of basin management on flooding and agricultural water use.