Research On Utilization And Regulation Of Rain And Flood Resources In Typical Urban Drainage Channels

At present,China's water resources are facing two extreme challenges:on the one hand,urban flood disasters occur frequently,urban development and people's security are seriously threatened;on the other hand,the contradiction between supply and demand of urban water resources is becoming increasingly acute.and often accompanied by water pollution,water ecological environment damage and other problems,resulting in the shortage of urban water resources is becoming more and more serious.In order to alleviate the contradiction between urban water shortage and the waste of rain and flood resources,it is imperative to study how to regulate and control water resources in urban rivers in order to improve the utilization efficiency of rain and flood resources.In this paper,taking the Liangshui River in Beijing as the research area,the one-dimensional hydrodynamic model of the main stream of the Liangshui River is constructed by using the HD module of the MIKE11 model software.Based on the historical measured data,the river roughness is deduced by Manning formula,and the accuracy of the model is verified.The evolution process of two typical floods is calculated by Muskingen Method and Characteristic river length Method,and the model is used to simulate the maximum water level change of historical flood to analyze the safety degree of typical water conservancy projects in flood control in the river section with overflow risk and on the main stream.Comprehensively evaluate the flood control capacity of Liangshui River after treatment,and judge the feasibility of its rain flood scheduling.Draw up and select the non-flood season water storage scheme and the flood season rain flood dispatching scheme which are more suitable for the study area,and analyze the water storage benefit and the rationality of the dispatching scheme.The main conclusions are as follows:(1)Based on the collected data,the channel of the main stream of Liangshui River is generalized,and the inverse roughness of water level-discharge relationship is established based on the measured data of Wanquan Temple Rubber Dam,Yangqiao Rubber Dam and Dahongmen Gate.The comprehensive roughness of the upper section is 0.035,the middle section is 0.030,and the lower section is 0.025.The one-dimensional hydrodynamic model of Liangshui River is established based on MIKE11 software.The model is used to simulate the typical flood water level process lines of"7.20"in 2016 and"7.21"in 2012,and compared with the measured water level line,the accuracy of the model is verified,and it is found that the water level line fits well.The model can accurately reflect the occurrence of flood in the main stream of Liangshui River.(2)The flood discharge capacity of the mainstream of Liangshui River is evaluated by setting the frequency of two floods in 20 years and once in 50 years in"7.20"in 2016 and"7.21"in 2012.First of all,the Maskin root algorithm is used to calculate the flood evolution process of each typical section of the Liangshui River.Secondly,by using the model to output the highest water level in four scenarios and comparing it with the top elevation of the left and right bank,it is found that there are several river sections with overflow risk in the river:water-blocking bridge sections such as the upstream section of Lianyu Bridge to Guangwai Street Bridge and the upstream section of Zhangcai Road Bridge,and the entrance section of the West fourth Ring Road,West passenger Station,South Station culvert,etc.Finally,the maximum flood level of three typical sections of Yangqiao Rubber Dam,Dahongmen Gate and Majuqiao Gate under four scenarios is calculated by the model,and compared with the design water level,the flood control capacity of each sluice dam is analyzed.It is found that Majuqiao Gate does not exceed the design water level in four scenarios,and the project safety degree is high.Yangqiao Rubber Dam has no hidden danger once in 20 years,and once in 50years exceeds its 50-year design water level,which is a relatively safe project.Dahongmen Gate exceeds its design water level in all four scenarios,and there is a great risk,which needs to be paid close attention to in flood season.In summary,it is found that through the planning and construction of flood control and drainage system and comprehensive control of water environment,the dikes of Liangshui River basically have the ability to realize the planned standard flood discharge except for a few stuck points.(3)Based on the main channel of Liangshui River which can discharge flood safely,the water storage scheme which is more suitable for Liangshui River in non-flood season is selected by model simulation and trial calculation as follows:”Yangqiao Rubber Dam drum dam 0.7m”,“Dahongmen Gate with two holes,gate opening 0.13m”,“Majuqiao Gate with three holes,gate height 1.4m”,“Xinhe Gate with two holes,gate opening 0.3m”,“Zhangjiawan Gate with two holes,gate opening 0.3m”.Through the Cross-section Method,the water storage capacity can be increased by 15700 m~3?7200 m~3?96200 m~3?172500 m~3?392300 m~3,the water surface area can be increased by 3800 m~2,1700 m~2,5500 m~2,4400 m~2and 7500 m~2.The water storage capacity of the whole river can be increased by 683900 m~3,and the water surface area can be increased by 22900 m~2.(4)According to the principle of rain flood operation in the main stream of Liangshui River,the scheduling scheme of each sluice dam in flood season is selected as follows:the rubber dam on the main stream all collapses.On non-rainfall days in flood season,Dahongmen Gate,Majuqiao Gate,Xinhe Gate and Zhangjiawan Gate welcome the flood season with"open 6 holes with an opening of 1.0m","maintain a water depth of 1.5m in front of the gate","open 11 holes with an opening of 1.0m",and"open 11 holes with an opening of1.0m"respectively.During the rising stage of the flood,the Dahongmen Gate first maintained the state of the flood,the Majuqiao Gate opened when it rained,and when the water level in front of Xinhe Gate and Zhangjiawan Gate is higher than the upstream service channel but lower than or equal to its designed normal water level,the discharge is all controlled by"opening 11 holes,opening 2.0m"to control the leakage.When the flood rises to the water level in front of the four sluices and exceeds its design water level,the floodgates are opened in time to control the flood.In the receding stage,when the water level in front of the four sluices is lower than the upstream service channel,the tail water will be stored timely according to the subsequent rainfall forecast.During the flood season,the whole river can increase the amount of intercepted tail water 668200 m~3,and the water surface area can increase 19100 m~2.