DISTRIBUTED RAINFALL-RUNOFF AND 2D FLOOD FLOWS SIMULATION USING HIGH-RESOLUTION SCHEME AND EXAMINATION OF EFFECTS OF RIVER IMPROVEMENT WORKS ON WATER LEVEL IN THE ONGA RIVER

Abstract

The numerical simulations of rainfall-runoff and flood flows in the Onga river basin were performed.The rain-fall runoffs were simulated by a distributed hydrological model using a high-resolution scheme.The flood flows in the main river and plural tributaries were simulated simultaneously by the 2D unsteadyfree-surface flow model with treatment of parallel computation and sink term semi-implicitly. Theflooding event in the Onga river basin in July 2003, 2009 and 2010 were simulated by the model. Thesimulated results were compared with the observed water level. It shows that the model is a useful tool forexamining the process of runoff and flooding in the Onga river basin. The effects of river improvementworks on the water level in the Onga river and improvement of computational speed were also examined.