| Debris flow is a disastrous geology phenomenon caused by the heavy rainfall in mountainous areas and it usually brings a great loss to local life and economic production.The numerical prediction model of debris flow is of great significance to the prevention and mitigation of debris flow hazards in mountainous areas.The present paper has established the numerical prediction model of debris flow in Jixian County by combining three methods of Hydrodynamic Theory,Sediment Incipient Motion and Analytic Hierarchy Process,and based on the rainfall prediction data of Weather Research and Forecasting Model.Some towns of Tianjin Jixian County were chose as the investigation areas.The present paper has applied the ArcGIS to clip raster data to obtain the DEM data of Jixian County,and extracted the river network information of the model region.The Surface-water Modeling System has been adopted to divide mesh for the investigation area,also the unstructured triangular and quadrilateral uniform step meshes have been generated.And the generated grid information has been read by the application program,so the relationship of unit,channel and node has been obtained.The hydraulic motion equation and continuity equation was dispersed by the Finite Volume Method,the flow velocity of surface runoff grid channel was simulated by Hydrodynamic model Theory,and calculated the water and momentum balance,so the channel velocity of rainfall would be obtained.Combined the Sediment Incipient Motion Theory and hydrodynamic model of debris flow formation as a basis for the hazard of debris flow,and the starting velocity has been calculated by using the model of sediment incipient,and determined the sediment particles start by comparing the threshold velocity of the sediment with the flow velocity of the grid channel.Through the analysis of debris flow formation conditions,terrain,geology,vegetation,geomorphology,human activities,historical influence,rainfall intensity and rainfall time was selected as risk factors,and each factor was weighed by the AHP method,so the AHP prediction model was established.The present paper has calculated the risk level of hourly grid according to the rainfall progress from 17 to 22 July 2012.And the prediction model was verified by the debris flow of Shuang'an in Jixian County,verification results showed that the moderate risk areas and high risk areas were included in the debris flow of Shuang'an,it meant the prediction model was certainly reliable.Then used the WRF numerical prediction and rainfall data from 16 to 21 July 2012 to predict debris flow hazard,highly dangerous areas did not appear in two rainfall data simulation results on July 20 and 21.The debris flow prediction results based on WRF prediction forecast data could be three days in advance to simulate the danger areas,which is beneficial to prevention and reduction of disaster in mountain areas. |
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