| Flash flood disaster is a form of disasters caused by precipitation in precipitation hills area and influenced by various complex factors, such as climate, geographical environment, rainfall and human activity. Flash flood disaster occurred frequently in ShanDong province. The prevention region under the threat of flash flood disaster covers an area of 49080 km2 and involves in 56 counties, expression form is given priority to mountain river floods. Flash flood disaster causes great threat to people’s lives and property safety, influences the social and economic development and the process of building a well-off society in an all-round way seriously.From 2009 to 2012,56 counties carried out non-engineering measures construction for flash flood disaster’ prevention and control at the county level, which has achieved good effect already. However, there are still some weaknesses in flash flood prevention and control work, such as the determination and application of early warning indicators. Based on the geological conditions, the basic data and the present situation of flash flood disasters in Shandong province, for the disaster form of mountain river flood, this paper will study the major problem focus on "what is the early warning indicators, how to determine early warning indicators, how to apply early warning indicators". The research contents are as follows:(1)The paper summarizes the basic definition, classification, gradation of early warning indicators and analyses the basic parameters of flash flood disasters’early warning indicator, including critical flow rate, rainstorm duration, warning time and soil water content. Considering layout of rainfall monitoring sites and the actual work needs, this paper uses the rainfall early warning indicators.(2)Two methods for determining the early warning indicators. The method of same frequency backstepping is based on the assumption of same frequency between rainstorm and flood, this paper selects seven typical threshold as soil moisture including Pa=0,0.2Wm,0.35Wm,0.5Wm, (2/3)Wm,0.8Wm and Wm, gets multiple rainstorm-frequency curves and peak-frequency curves through rainfall runoff analysis, sets up soil water content-time-critical rainfall curves, makes dynamic early warning relatively coming true; The method of watershed hydrological model based on the HEC-HMS sets up basin model using GIS technology and DEM, simulates rainfall runoff process, assumes a value of rainfall and simulates flood process on control section, with continuous trial until the flood peak is equal to the critical flow rate, the critical rainfall can be obtained. Finally, determines the early warning indicators considering the channels’ characteristics, response time and sites’ location.(3)Typical design of application system for flash flood disasters’ early warning indicators. Based on monitoring and early warning platform and early warning indicators, uses Adobe Flex and Jave, this paper designes and developes application system of early warning indicators, which has data storage, data query, visualization and dynamic early warning and other functions. The system can be used as part of the monitoring and early warning platform in actual prevention and control work, implements efficient and accurate dynamic flash flood warning.(4)The actual engineering application. This paper selects Zhudong River watershed in Pingdu City, Qingshan and Xigejia villages as typical objects of disaster prevention, uses two typical method to determine early warning indicators, shows the results of practical application by the system. Through analysis and research, it is considered that the hydrological model based on HEC-HMS method has the most value for popularization; implementing the perfect combination of this method and the application system is an important development direction of flash flood dynamic early warning in Shandong Province. It has very good application prospect. |
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