Research On Design Flood For Ju Ru River Basin

Flooding is an important and complex hydrologic phenomena in nature. Flood prevention has attracted more and more attention with the rapid development of social economy and urbanization process accelerated, and the design flood has a close relationship with the safety and economy of project construction and safety of people’s life and property. The design flood is the most basic for watershed planning and channel management, and plays a very important role in guaranteeing security of people’s life, property, urban construction safety and the sustainable development of social economy.《The Planning of Pinggu New City(2005~2020)》increases the flood prevention standard from once every 20 years to once every 50 years of the Ju and Ru river which passing through the planning construction area of the new city. According to the new flood prevention standards of Pinggu new city, it is necessary to calculate the chosen channel sections’ peak discharges of design flood for every 10, 20 and 50 years.In the context of the Planning, we remeasure the Ju Ru river basin’s parameters, get the reservoirs’ drainage flood through recalculating three large and medium-sized reservoirs’ design flood and flood regulating calculation, calculate the design interval flood by the method of comprehensive unit line and rational formula, calculate the combined flood by superposition taking the flood propagation time into account, analyze the key role of the channel storage using the one-dimensional flood routing simulation model and propose Ju Ru river’s peak discharges of design flood for every 10, 20 and 50 years after comprehensive analysis, finally we analyze the rationality of the proposed design flood and give the conclusions and recommendations.Main research contents and results of this research are as follows:(1) We select the calculation cross-sections taking Ju Ru river’s tributaries and design purpose into account. We remeasure the Ju Ru river basin’s parameters using GIS software, 1:50000 DEM and 1:10000 topographic map considering the change of basin’s underlying surface conditions and river flood prevention and drainage standards.(2) The design flood of every chosen cross-section is combined of reservoirs’ drainage flood and interval flood. We derive the reservoirs’ drainage flood from recalculating three large and medium-sized reservoirs’(Haizi reservoir, Huangsongyu reservoir and Xiyu reservoir) design flood and flood regulating calculation based on reservoirs’ design flood, water level ~storage capacity ~drainage discharge curve and flood prevention scheduling scheme; The design interval flood is derived from the design storm due to the lack of measured data, the peak flows of interval flood is calculated by the method of comprehensive unit line and rational formula, the flood process is calculated using the Beijing mountain area’s standard flood process curve and corrected.(3) We calculate every cross-section’s combined design flood by superimposing reservoirs’ drainage flood and interval flood taking the propagation time into account, we analyze the key role of the channel storage using the one-dimensional flood routing simulation model and finally propose Ju Ru river’s peak discharges of design flood for every 10, 20 and 50 years after comprehensive analysis.(4) We provide corresponding basis for flood prevention and water system planning of Pinggu new city through analyzing the rationality of the proposed design flood by comparing with the original designs, historical investigations and the HEC-HMS model calculation results.