FIELD INVESTIGATION OF STORMWATER FLOWS IN AN URBAN SEWER SYSTEM AND A RECEIVING STREAM

Abstract

 Rainstorm-induced flood is one of the most challenging issues in the world. The management of flood disasters necessitates a clear understanding on associated flow characteristics and drainage mechanisms. This paper presents a field survey on the stormwater flows in a urban drainage system, focusing on the flow properties in a sewer pipe and a receiving stream. In particular, the influences of precipitation patterns, tide levels and drainage discharges from the pumping station have been analyzed. According to the results, the water level changes in the receiving stream are strongly dependent on the hyetograph. Classifying the precipitation patterns into intermittent rain, rain shower and continuous rain, the differences in the sewer flow responses are clarified. The pressurized flows, backflows from sewer pipes to open canals and backwater effects from downstream pipes and the pumping station are confirmed, which are important mechanisms of pluvial floods. The drainage discharge from the pumping station leads to an increase of water levels in the receiving stream both upstream and downstream, which may increase fluvial flood risks. The findings are of great meaning for integrated management of sewer-river systems to prevent/mitigate flood disasters.