Diagnostic analysis of waterlogging in Zhenjiang City by using PCSWMM

Abstract

Urban flood becomes a more and more serious problem in China now resulting from the urbanization. Compared with traditional methods, numerical model simulation is a better approach to analyse and evaluate the urban flood risk, waterlogging area and flooding depth. Taking a historical flooding area in Zhenjiang as an example, this paper analysed the operational causes of the waterlogging in an observed 4-day precipitation event by PCSWMM. The results showed that the waterlogging area was reduced up to 77% when the drainage pump was operated appropriately. With the pump turned on, the discharge rate increased from 0.2 to 2.04 m3/s and maximum water depth in flood area dropped from 0.9 m to 0.66 m. It indicated that the severe waterlogging in the study area was primarily resulted from the improper pump operation in the 4-day event. However, simulation resulted that even with appropriate pump operation; there was still 0.5 hectares of waterlogging area. In addition, the effectiveness of the drainage pipe system on the waterlogging reduction was evaluated with existing and planned conditions. The results showed that updated pipe system with a diameter of 1000-2800 mm could hold a discharge flow rate up to 3.5 m3/s. The study imply that combined of appropriate pump operation and pipe system updating may effectively improve the drainage capacity of the whole pipe system and reduce the waterlogging risk around crossroads.