Determination of design return period for urban storm-drainage systems

With the feasibility study of the storm-drainage system in Yizhen City of Jiangsu Province as an example, the influences of design return period on the construction cost of the storm-drainage system are analyzed. It is pointed out that the determination of the design return period should be done for each catchment according to function regionalization, so that the storm-drainage system can meet the requirement of drainage and economy. Finally, some suggestions are proposed for improvement of standards for design rainfall return period.