Scenarios Comparison Research Of The Prevent-flood Dams' Effect On Floods In Xunjiang River Basin

Hydraulic installations, especially the flood defense buildings themselves, usually do negative influence to prevent flood, which attracts more and more people's attentions now. The main purpose of this paper is to seek a best applicable method to analyze the effort of flood defense dams to the floods, compute its influence degree and other problems in the Xunjiang river basin. The main research contents and achievements are listed as fallows:1. By investigating the construction and collecting the basic data on the flood defense dam along Xunjiang river, I make a statistic describing the dam's protection areas in different water level, and also construct the storage-capacity curve of these areas; and get the information on construction of the flood defense dam. The largest storage capacity in the Flood is 5.630 × 108m3~ 31.94 × 108m3, it's 2.34% ~ 9.50% accounting for the greatest proportion in total flood runoff.2. Analyze 8 representative floods' characters and their corresponding rain- storms' character, which are representative in the Xunjiang and Xijiang river basin.3. Muskingum flood routing process, single section water conservation method, hydrodynamic characteristic runoff mathematical calculations and beach sluggish flood storeroom adjusted factor etc., are the best methods to quantitatively analyze and calculate how the dams effort flood runoff, then apply the height-runoff relationship line and calibrated factor method to reckon the water height change progress when the floods go back to troughs or go through troughs respectively.4. According to the flood wave movement principle in hydrology, it was analyzed that how the dams effort the time of flood movement, and use hydraulics Manning equation to get the coarse rate in every reach according to the surveyed water table line and the plane, vertical, horizontal sections' data. It's my opinion that there is no very distinct difference in the flood move time before and after the dam was built. The dams of Xunjiang river do little effort to the coarse rate of beach.5. Though synthetical analysis and evaluate the research achievements, the result obtained shows that the dams just do a small effect to the flood of Xunjiang river and Xijiang downstream river.