Scenario Analysis Of River Network Structure-storage Capacity-flood Based On Simulation By SOBEK

As the main natural calamities in the regions of coastal plain, flood damage has caused heavy loss of national economy, so the prophylaxis and treatment of flood damage has become the focus of the international community and academic circles. Shanghai is the hub of opening to the outside world, North-south exchange and East-west linkage, also is the economic powerhouse of China. But the flood damage of Shanghai is the most heavy natural calamities, which causes extremely serious social economic losses.Financially supported by the National Natural Science Foundation of China (40730526), this paper uses SOBEK model to simulate the change of river network,the process and characteristics of flood damage, to establish association of floods-river characteristics. At last, the strategy of determination and adjustment for the structure of river network used in the benign flood management model. The research of scene analysis for the flood damage of Shanghai, can provide certain theoretical basis and scientific proof for the formalization of flood control and the management of waterlogged elimination, the river realignment and the planning scheme of river network and the model of sustainable development. Based on the review and summary of the present situation of Shanghai flood disaster and the theory on how to take precautions against natural calamities, This paper includes main works as follows:1. This paper makes a study of Shanghai flood disaster features, hazard-formative factors and the mechanism of the flood disaster effect. The occurrence of flood disasters in Shanghai and the degree of characteristics change in 1949-1991 is analyzed. There have a downward trend of the flood frequency and an alleviative trend of the flood extent in selected period in Shanghai, although the rainfall and maximum tidal level of Huangpu River have been being rising and the natural flood control capacity was going down. Flood control engineering efficiently decreased the occurrence and effect of floods.2. A study of mechanism in Shanghai between flood disaster and hazard formative factors. Changes of flood-causing factors were well responded to the process of urbanization and regional environmental change. The flood causing way of each factor was different, rainfall and tidal level would affect flood occurrence and extent instantly and the impact of river disappearance on flood would lag 2-3 year and last for 4-5 years. Multiple regression analysis showed that the frequency trend of floods could be predicted by indicators of annual maximum tidal Level in Mishidu station, the annual number of river disappearance and the flood season rainfall.3. The model of tidal river in plain is established, the effectiveness is validated. The scenario of tidal river structure is set, the storage capacity of the scenario is calculated4. River structure-storage capacity-flood disaster scene design. According the question how river structure of flood storage effect ability this problem, scene into flood type scene, river elements scene and river elements situation of recursive type control variable method situation design. Choose Meiyu flood course in 1999 (extreme Meiyu), Meiyu flood course in 2007 (typical Meiyu), flood course of 2009 Morako heavy rains as typical flood situation. For the river channel elements scene wide, respectively riverbed roughness design, river elements scene into rivers bending degree scene, inflow Angle scene, inflow position scene, river rate situations.5. The set and storage capacity of river net under the pressure in hydro-geomorphic factor is also done. River hydraulic model calculation results are shown:With scenario of keeping the same ratio of river channel area, tributary in upstream is more effective in decreasing flood peak compared with that in downstream, the more smaller of intersection angle of tributaries, the more stronger capacity in controlling flood. With scenario of increasing the river channel area,â‘ River storage and control capacity enhanced with the increasing of river curvature, and the per-unit capacity of the river area reaches the peak value when river curvature is 2.8.â‘¡River storage and control capacity enhanced with the increasing of river channel area but there exists a peak value. When the ratio of river channel area is between 3%-5%, the increasing of per river area unit has the best affection in decreasing peak flow.â‘¢To increase tributary area might improve the river network storage and flood control capacity more effectively than to increase the mainstream area.6. The design and analysis of river net under the pressure in hydro-geomorphic factor is also made. Results of river structure-storage capacity scene simulation under the pressure of hydro logical and landform factors showed:The longer time flood process lasts, the strongger natural river of storage capacity is; River storage capacity can be magnified and river net structure-storage function response mechanism can be strengthen when river channel roughness increases.7. The design strategy of plain tidal river flood control and water drainage like Shanghai whose urbanization degree is very high, was proposed. The other Prevention and management strategy about flood protection was also put forward.Propose the management strategy of fitting water net structure to improve the state of city food and water environment.