River Flood Risk Analysis And Research On Provincial Flood Risk Maps

China is one of the most frequent flooding countries. Flood disasters seriously threaten the civil lives and restrict the sustainable development of social economy. In recent years, people have come up with practical experience in flood fighting, and put forward the new flood control concepts which transform'flood control'into'flood management'. Flood risk management is the core of flood management. But the lack of awareness of flood risk hampered the development of new flood management strategies. And the lack of continuous, complete and accurate flood risk information of flood plain will delay the emergency management and rational decision-making. Therefore, the risk analysis of flood zone is in an emergency. Flood risk map will display the risk information to decision makers and the public. And it will improve scientific decision-making and enhance public awareness of flood risk.In the paper, the middle and lower reaches of Liao River and its protected zone are taken as the case studies. Based on the numerical simulation of flood, downstream embankment and protected area's flood risk, the provincial flood risk mapping system are studied, respectively. The main research results are summeried as follows:(1) Changes of external factors have significant influence on flood control capacity. In this research, river flood routing model was established. Flood control capacity of embankment is checked through comparing characteristic level of the dike with the embankment elevation and simulated water level. The model roughness of river main channel and flood land is calibrated by means of historical floods. Then, the design flood routing is simulated. At last, the simulation results are validated by water surface profile which is calculated during dike design. The results that flood control capacity of downstream embankment of Shifosi reservior is validated show that this method has better practicality and convenience and present levee can defense the design standard flood.(2) Crash types and breach characteristics of embankment are analyzed. Different calculation methods of breach flow were compared and analyzed the impact of breach parameters on floods. The results show that by the significant effects of the water level difference inside and outside the dike, the results of weir flow equation and piping equation are better than the results of the energy equation. Among them, the weir flow equation adapts to damage caused by overflow; the piping equation adapts to infiltration and sabotage. Both methods can simulate the flow process of the dike-breaking flood. The occurrence time and the maximum width of dike-break are the main factors on outflow. A flooding model coupled one-dimension with two-dimension is established, and flood inundation is simulated under the circumstance that wheter the roads delay the flood procession. Simulation results show that roads play an important role in delaying the flood evolution.(3) In view of the population and developed areas mainly localized in the middle and lower reaches of rivers, discussed the river flood risk mapping methods and draw the flood hazard mapping in left bank of the Liao River. Finally, the construction of the provincial flood risk mapping system has been studied, the system is more conducive to the establishment and use of flood risk maps.(4) Flood damage assessment of flood plain is an important reference for policy makers. Existing statistical data are sorted and putted into database. And the flood information which is got from flood simulation results analysis and convertion of different conditions is distributed to the affected area using ArcGIS software. The flood damage assessment model is constructed and exceeding standard flood damages are evaluated using former model. Flood inundation area, affected villages, the loss of population and others are calculated. As a result, the optimized flood control measures are chose through the comparison of various programs of flood damage assessment.(5) Liao River regions are the rapid economic development regions, but also key areas for flood control. A strategy of "regional defense, district management, joint scheduling" is adopted based on zoning by dikes, roads and other linear water-blocking material. As the flood differences and geographical relationship between Liaohe River and Hun River, by engineering measures leading flood from Liao river to the Hun River, the the flood pressure of Liao river can be reduced. A controlled flooding can ease the flood pressure, but also bring ecological benefits. However, there is always the likelihood of a breach occurred,developing emergency response and evacuation routes.At last, the paper has given some conclusions, as well as the questions which still need a fruther study.