Optimization of Overflow from Storm Sewer System Based on Storm Return Period

According to Tianjin Municipal Engineering Budget Price,a model for construction cost of storm sewer system was built.Five low-cost schemes were found by enumeration algorithm and by applying global search under given conditions of design flow,original buried depth and length of pipe.The cost of these five schemes decreased by 10.13%,9.47%,6.25%,5.57% and 4.82% respectively compared with the originally planned scheme.The overflows of the above five schemes in different storm return periods were simulated by SWMM.The quantitative relations of overflow risk to storm return periods and structure of storm sewer system were determined.All six schemes would lead to node overflow,pipe overload and high load of pipe drainage in different return periods except for 0.5 a.