ESTIMATION OF FLOODPLAIN ROUGHNESS AND DISCHARGE HYDROGRAPH USING WATER LEVEL HYDROGRAPHS AND 2-D NUMERICAL SIMULATION

Abstract

Accurate estimation of discharge hydrograph during flood events has been one of the most important issues in River Engineering. In this study numerical simulations of flood flows in a compound meandering channel are carried out using a 2-d numerical model to discuss the possibility to reproduce the discharge hydrograph only with the information on water levels. It is demonstrated that the numerical simulation with water level hydrographs at upstream and downstream boundaries can well reproduce the discharge hydrograph at the section in the middle reach and hence that the discharge hydrograph at upstream end is not always necessary. It is also shown that since discharge hydrograph is very sensitive to the magnitude of floodplain roughness, even a record of flood discharge at high water stage, not necessarily at the flood peak, may give good estimation of floodplain roughness, leading to highly accurate estimation of discharge hydrograph.