Benefit Analysis and Improvement Measures against Typhoon In-fa of Hangzhou Sanbao Drainage Project
The Sanbao Flood Control and Drainage Project is one of the important node projects for flood control and drainage in Hangzhou,especially with direct disaster prevention and reduction benefits for reducing the water level of the canal.There was heavy rainstorm all over the city of Hangzhou under the influence of Typhoon In-fa from July 22 to 27,2021,which caused flooding beyond the warning level in the canal watershed(the Hangzhou section).Sanbao Drainage Sluice-Pumping Station was started up in time to discharge flood and continuously operated to lower the water level of the canal network,effectively ensuring the safety of urban operation.In order to enhance the effectiveness of Sanbao Drainage Sluice-Pumping Station,the engineering operation,rainfall and water conditions during the"Typhoon In-fa"period were analyzed in this study.Three possible situations for water volume during the typhoon impact period were calculated according to the flow direction of the canal,and the possible water discharge into the canal during the typhoon impact period were 9.6 million m3,17.63 million m3,and 11.55 million m3,respectively.In addition,the highest water level of Gongchenqiao Station decreased by 0.41m as the Sanbao drainage project was finely scheduled,and the duration of exceeding the alarm limit has been reduced from 142 hours to 26 hours.Based on operational practice,regarding the water blocking problem of garbage accumulation and trash racks during flood periods,improvement measures have been taken to adjust the elevation of the trash rack crossbeam and increase the distance between the trash racks to increase the water inflow,significantly improving the drainage efficiency.In response to the problem of passive tidal avoidance of the unit,measures are proposed to improve the design recurrence period and optimize the model of the wide head section water pump impeller,ensuring the stable operation of the water pump unit and providing reference for the design and construction of urban strong discharge pumping stations in strong tidal river sections.
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