Research And Application Of Flood Forecasting Based On HEC - HMS And Xin'anjiang Model

The LiJiang upstream basin is one of the basins which torrent disasters occured Seriously in GuangXi.Due to LiJiang upstream basin is one of the rainstorm’s centers. This led to the torrent disasters occured frequently. Therefore, this paper take the LiJiang upstream watershed as the research object. Building lijiang upstream digital watershed Based on DEM and land use, soil type and exploring for scientific and reasonable schemes of flood forecasting for the lijiang upstream watershed. Providing theory and method support for the flood control and disaster mitigation.Floods events were simulated by hydraulic modeling system HEC-HMS:SCS curve number loss model was selected to compute runoff volumes, Snyder unit hydrograph model was selected to compute direct runoff, Baseflow was modeled by exponential recession, Muskingum was used to model channel flow.Then, Analysising the sensitivity of parameters with the modified Morris Method. According to the results of sensitivity analysis:the most sensitive parameter was CN followed by Cp、Lag time、K.Further, Optimizing the parameters and Amending the SCS-CN AMC hierarchies.After calibration and validation, in calibration period:The Percent of pass was 81.5%, The average deterministic coefficient was 0.809. In validation period:the percent of pass was 75%, the average deterministic coefficient was 0.76.Floods events were simulated by hydraulic modeling system Xin’an model and we selected the same floods events as HEC-HMS. Building the model:Evaporation module adopts three layer evaporation calculation model. Natural storage model was selected to compute runoff volumes. The runoff was divided into surface runoff, interflow and underground runoff by the free water reservoir. Surface runoff was calculated by using the unit hydrograph model, interflow and underground runoff was calculated by using linear reservoir method. After calibration and validation, in calibration period:The percent of pass was 85.2%, the average deterministic coefficient was 0.850. in validation period:the percent of pass was 87.5%, the average deterministic coefficient was 0.87.The results show that:HEC-HMS model and Xin’ an model forecasting schemes are applicable to the LiJiang upstream basin. Both models can provide a reference and technical support for the Flood forecasting in LiJiang upstream basin.