The Discuss about Xijiang River’s Effect on Beijiang River Flood Control

摘要

To reduce flood disaster for the downstream protection area, the flood-protection measures will be taken by reservoir retention or flood storage region retarding. By calculating different control plans of Feilaixia Reservoir and/or diversion area under the circumstance of 4 design floods of 2%, 1%, 0.5%, 0.33%, thesis analyses and compares their effect on reducing of flood for the downstream. The “experience control operation method” is used in Feilaixia reservoir at present. The “ideal operation method” having calculated the intervening inflow between dam site and Shijiao station on preliminary design report will be used in future, it controls the discharge released from Feilaixia reservoir according to safety discharge from Shijiao. The flood back-up from Xijiang River hasn’t been taken into account in the two operation methods. According to the historical floods, the analysis of the meet of Xijiang River flood and Beijiang River’s downstream flood has been done. The Beijiang River’s floods were back-up by Xijiang River’s flood while flood appear at the same time in two rivers, the back-up water level was caused in Beijiang Dadi which is the most important dyke in local region river reach. The cases of flood meet or no flood meet in the downstream of Beijiang River were calculated under 1% design flood routing, the water surface profile in Beijiang Dadi reach has been plotted. Obviously, the increase of water level caused by flood meets is larger than decrease caused by flood retention of reservoir. So, when we take measures to control the flood of Beijiang River’s downstream, we should take into account not only the discharge from upstream and intervening inflow but also the real-time flood forecasting of Xijiang River. To reduce the back-up water level and mitigate the flood prevention pressure of Beijiang Dadi dyke, it is better to avoid the meet of the flood peaks of two rivers by utilizing Feilaixia reservoir regulation