Design Flood Research Of Urban Drainage (Waterlogged) River

River, as the main passageway of urban drainage plays a critical role. In this paper, based on Meishe river catchment in Haikou city, which can release flood and drain water-logged, was selected to study the design flood problem. Meishe river catchment has two parts: natural catchment and urban catchment, which have different methods to calculate design flood. This paper focused on the research of design flood and river flood routing, and the specific research contents and conclusions are as follows:(1) Based on 43 years rainfall data, the design storm process was calculated. The concrete content includes: statistics multiple periods rainfall with annual maximum method, design storm frequency analysis, selection of the typical storm and design storm process calculation. Based on the above, the 24-hour design storm processes of 20%, 10%, 5%, 2% were calculated.(2) Runoff in urban and natural areas was calculated based on design storm. Due to few methods of calculating urban design flood, urban comprehensive runoff method was put forward for needs. Firstly, based on heavy rainfall on July 18, 2014 in Haikou city, the runoff of 52 drainage areas were calculated by using urban comprehensive runoff method and urban derivation formula method. Then, the practicability of urban comprehensive runoff method was verified according to comparisons between their results and the actual water logging conditions. Secondly, by using urban comprehensive runoff method, the runoff of the urban part of Meishe river was calculated, with considering limiting discharge situation of networks in drainage districts. The natural areas' runoff, using the comprehensive unit line and derivation formula method of Guangdong province calculates, was also calculated, meanwhile with considering ShaPo reservoir flood regulating effect.(3) Based on the design flood of natural river basin and urban area, the fluvial flood of Meishe River was analyzed. The watercourse flood routing process was simulated under four frequency(20%, 10%, 5%, 2%) and three situations(no hydraulic structures, adding bridges and adding rubber dams). Under the situation of no hydraulic structures, the flood routing model appears flood overflow at 5% and 2% frequency, so the flood discharge capacity of Meishe River is less than 20-year frequency flood. The bridges have little influence on fluvial flood, but the water level and flow of the bridges' upstream and downstream section have significant changes. In the case of small recurrence interval, rubber dams have great influence on flood water level and flow. And the influence of rubber dams becomes less along with the increase of recurrence interval.