Analysis on the Main Factors Resulting in Flood Disasters in the Weihe River Watershed and the Control Measures

The area of the Weihe River Watershed is 1.35×10~6 km~2,in which the area in Shaanxi Province is 3.36×10~4 km~2 and occupies 53% of the total area of the watershed.The mainstream of the Weihe River is 818 km in length,its catchment area is 6.24×10~4 km~2,and its annual runoff volume is 1.01×10~(10) m~3.The length of the upper reaches from the headwaters to the Baoji debouchure is 433.4 km,the river channel is narrow,the water current flows torrentially,and the silt content is high;the length of the middle reaches from the Baoji debouchure to Xianyang Bridge is 176.6 km,the river channel is wide and shallow,sand bars are extensively distributed in the river channel,and the water current flows gently;and the length of the lower reaches from Xianyang Bridge to the Tongguan embouchure is 208 km.In the Weihe River Watershed it belongs to the continental monsoon climate,it is cold and dry in winter but hot and rainy in summer,the average annual precipitation is 683.6 mm and can be up to 1 000 mm in some regions,and the precipitation occurs mainly during the period from July to October,which occupies over 60% of the annual precipitation.In this paper,the interannual,annual and monthly change of flood disasters in the Weihe River Watershed and the change of elevation of Tongguan since recent 50 years are discussed,and the main factors resulting in the flood disasters,including the interannual,annual and seasonal change of precipitation,serious filling-up of the river channel and embouchure,deterioration of the flow status,etc.are analyzed.Aiming at these factors and the characteristics of flood disasters in the Weihe River Watershed,some measures are put forward for controlling flood disasters,they are to reduce the elevation of the lower reaches,decrease the filling-up of the river channel and embouchure,increase the flood-passing capability of the river channel,erode the deposited sand in the river channel by artificial floods from reservoirs,especially the lower reaches,construct and reinforce the flood control projects so as to increase the flood prevention and control capability,regenerate the natural vegetation so as to control soil erosion and reduce the silt content of the river,etc.