Simulation Of The Taihu Lake Basin Flood Risk

Taihu Basin is the most developed region in China, but it suffers from frequent flood and tremendous loss due to abundant rainfall (unevenly distributed in time and space), plate like topography and influence of high tide at boundary. After accomplishment of basin treatment framework projects, the flood control situation changed significantly. It is necessary to research how to enhance capacity building for coping with the changes of flood risk due to global warming and rapid urbanization on the base of current status. To make the research more scientific and the result more referable, quantitative analysis should be carried out based on current directive conclusions in order to get more accurate understanding about the influence of factors such as rainfall change, sea level rise, land use and etc.Basin scope numerical model is a new technology for research oriented to objectives above; it has large space for future development and is widely carried out in the world. However, currently there are some key problems in this field that need research:﹍arge calculation area involves thousands of targets, which needs hydrological, hydrodynamics and metrological to deal with respectively;﹍arge scale numerical model has significant difference with detailed model, such as objects abstraction, parameters figuring and calculation objectives;﹖here are many factors in Taihu Basin that affect flood risk distribution, if digital simulation is carried out one by one, the quantity of calculation task will be so tremendous that it is hard to accomplish and unnecessary also. The author refines the more important factors based on analysis of situation of flood control in the Taihu Basin, then figures out the most likely change of them and reflect it in the numerical model quantitatively, and therefore has got several representative scenarios and carried out simulation on them. Finally, some understanding and suggestions about strategy of flood control in Taihu Basin are proposed based on analysis of the simulation results of different scenarios.The technical routine of this paper can be summarized as:following the discipline of maximized utilization of available resources, search or develop adequate numerical model to reflect the influence of key factors such as climate, rainfall runoff, river network and pumping, use appropriate cooperative calculation technology to join models to build basin-scale model, which is used in further Taihu Basin flood analysis. Make research on the most likely change of various factors and set out several scenarios accordingly, then the conclusions can be drawn by comparing different scenario results. The task and conclusions of this paper can be divided into four parts:1. Study the current situation of flood control in Taihu Basin and make analysis on its layout; search available numerical models for target suitable for basin circumstance and this research; investigate world-wide joint calculation technologies and figure out their characteristics.2. The paper proposes a newly developed river hydrodynamic model. Considering the characteristics of river in Taihu Basin, the model uses finite volume method base on LAX explicit scheme and chooses "graph" data structure to describe the complicated connectivity of channels in basin. The model can reflect whatever topography and deal with cross gate and dry bed gracefully. It possesses good stability, maintenance and runtime efficiency. By comparing the calculated result with field data, it’s believed that the model can simulate the flood movement in channel of the Taihu Basin with enough precision.3. A new technology base on COM, AUTOMATION, named pipe communication and multiple processes synchronization has been developed to solve the problem of connect multiple numerical models and carry out joint calculation task. It possesses the advantages of open structure, high tolerance, little additional restriction, easy accomplishment, high efficiency and flexible application. It significantly decreases the requirement of technicians in other fields, achieves maximized utilization of current numerical model resources and make real model database and calculation center possible. Proved by practical usage, the technology developed in the paper fully achieved expected objectives and successfully built the Taihu Basin model.4. Based on the model built above, Taihu Basin flood risk simulation was carried out. Considering the current flood control situation, the most likely change of various factors was set out and quantitatively embedded into corresponding scenarios such as:rainfall increase, sea level rising, boundary pumping capacity increase, land use change, dispatching rule change and internal pumping capacity increase. Through the simulation results of different scenarios, the quantitative influence of factors was figured out and some understanding and suggestions were drawn out about the flood control strategy in Taihu Basin. The paper made some new progress in the basin-scale model building and flood scenarios simulation at large scale. The technical routine and results can be referred for research of large scale digital model construction and analysis of flood risk changes based on simulation results in other regions.