Calibration Instantaneous Unit Hydrograph Used for Flood Forecast of Existing Bridges

Based on instantaneous unit hydrograph,calibration instantaneous unit hydrograph method is put forward to forecast flood of existing bridges: instantaneous unit hydrograph is calibrated depending on water marks on piers left by historical flood and the corresponding rainfall series;by means of calibration instantaneous unit hydrograph,flood-peak stage and peak time lag is forecasted.In the whole process,water level-flow function is established beforehand to switch from flow to water level directly;biquadrate polynomial fitting is done at high flow segment of flow duration curve getting from instantaneous unit hydrograph.The study shows that this new method is rational in theory,convenient in practical application,reliable in computational accuracy,and can forecast flood disaster ahead of time to gain precious preparation time for guarantee traffic safety and flood fighting.So it will have good prospects in the aspect of forecast flood disaster of existing bridges.