The Estimation and Application of Design Rainstorm Intensity in Tianjin Area

The design rainstorm is an important foundation for the construction of flood control and drainage facilities. It is significant to improve the design rainstorm for strengthening the response to the regional flood and urban waterlogging disaster risk, which has been increasing with climate change and social development. However, the regular observations of rainstorm from general weather stations are insufficient for estimating the intensity of design rainstorm in urban drainage. It has been of great significance to maximize the use of regular observations to geographically refine the design rainstorm in urban drainage. Therefore, two weather stations from Tianjin urban and Tanggu districts with long period of precipitation-in-minute records, are chosen to estimate the intensity of design rainstorm and fit the intensity formula. Two methods are used in data sampling, one collecting the annual maximum and the other collecting multiple values per year. The comparison of the two locations indicates that the design rainstorm intensity in Tanggu district is much greater than that in the urban district. As a result, the drainage design at Tanggu district should be different from the urban district. Otherwise, Tanggu district would be confronted with greater risk of urban waterlogging disaster. The comparison of the two intensity formula suggests that the one based on the annual-maximum sampling is applicable in drainage design for the return period of 2—10 years. The application scope of the estimated design rainstorm intensity using regular observations is also pointed out for urban drainage. This provides a realistic reference for further spatial refinement of urban drainage design rainstorm.