| Numerous rivers with complex and diverse topographical features lead to frequent flooding in Tongnan region of Yangzhou.The application of hydraulic model of river network in this area can systematically analyze the drainage capacity of current river network and various planning schemes,which has direct guiding significance for formulating scientific and rational regional drainage planning.Through comparative study,this paper chooses a more accurate calculation method of sluice flow capacity suitable for the river network area of plain,and applies it to the calculation of unsteady flow in river network.The runoff generated by different frequencies of rainfall is obtained through calculation of runoff yield concentration.By using the Preissmann Weighted Implicit four-point scheme,the Saint-Venant equations are discretized in time and space.The unsteady flow mathematical model of Yangzhou Tongnan river network thus established is solved by relaxation iteration method.According to the measured data,the mathematical model is calibrated and verified.By using the calibrated and verified hydraulic model of river network,the present river network flow in Tongnan area is simulated numerically,and the water level and discharge values of the important nodes in the river network are obtained under the conditions of 50%Yangtze River drainage tide and drainage tide in the same period in 1991 encounter the case of once-in-twenty-year,once-in-ten-year and once-in-five-year rainfall.The current river network can basically satisfy the drainage requirements of once-in-five-year rainfall.However,in the case of once-in-ten year and once-in-twenty-year rainfall,the current river network can’t satisfy the drainage requirements.Under the comprehensive judgment,the current river network needs to be comprehensively rectified.From three aspects of river regulation,expansion of Tongjiang sluice and newly build Yangwan sluice,three kinds of comprehensive regulation planning schemes are put forward.The hydraulic model of river network is used to simulate and analyze whether these three kinds of schemes can saticfy the requirement of drainage in the region when 50%Yangtze River drainage tide encounter once-in-twenty-year rainfall.According to the simulation results,the first planning scheme "river regulation”and the second planning scheme "river regulation&expansion of Tongjiang sluice" do not saticfy the requirements of drainage in this area;the third planning scheme "river regulation&expansion of Tongjiang sluice&newly build Yangwan sluice",the calculated maximum water level of nodes are lower than the water level of drainage in Tongnan area,the third planning scheme is able to saticfy drainage requirements. |
