The Study Of The Causes For Waterlogging Disasters In Depression Along With Huaihe River Based On GIS

Huaihe River Basin, which located in climatic transition zone betweennorth and south of China, is vulnerable to the threat of flooding with theunique topography conditions. Since the21st century, with changing ofclimate and severe interference of human activities, abnormally largerainfall occurs frequently, which leading to extreme precipitation floodevents, and the proportion of waterlogging losses in the floods increasinggradually, so it is necessary to analyze the causes of waterloggingmechanism systematically, in depression along with Huaihe River.Based on regional disaster system theory and ArcGIS techniqueplatform, the related theory research progress of natural disasters at homeand abroad are mainly introduced in this paper, and the essential factors ofhazard inducing environment, the disaster-causing factor and hazardbearing body also be analyzed, as well as the formation mechanism ofwaterlogging be described.(1)The essential factors of hazard inducing environment are analyzedin survey region. The rainfall, main factor of climate, are analyzed withdifferent temporal scales (such as year, flood season, major flood period,Meiyu period,1dmax、3dmax、5dmax、7dmax、15dmax、30dmax), as wellas the precipitation-concentration degree (PCD), precipitation concentrationperiod (PCP)and grade analysis method; the digital elevation model(DEM) isestablished by topographic, in order to extract the topography information insurvey region, including slope, aspect, ground roughness, watershed flowdirection, flow direction, flow accumulation, flow length and so on; the soilcomposition and land-use change and its contribution to the formation ofwaterlogging are analyzed in this survey region; the relationship between highestwaterlogging water level and rainfall in different periods are analyzed, as well asthe different levels of days and contribution by grade analysis method. Resultsshow that, the topography and high water level of drainage area are sensitive towaterlongging, the stability of precipitation and the subsquently environmentalstability is low, which easily caused waterlongging disaster. (2)Disaster-causing factor analysis in typical years. Based on the regionaldisaster system theory, referring to the definition of disaster-causing space, theabnormal elements in hazard inducing environment, which called disaster-causingfactor, determines the threshold is analyzed, and the strength and coefficient ofrisk by using2005as the base year is calculated in this paper. It indicates that thelarger of rainfall in survey region, the higher and longer duration time of waterlevel in the drainage area, the greater risk of disaster-causing factor.(3) Factor analysis of hazard bearing body. The type and value of the hazardbearing body, and the principle of crops reduction under submerged conditions areanalyzed in this paper. According to the rice loss rate model in submergence,inundated time is determined by dissatisfying self drainage conditions on the basisof the comprehensive analysis between the highest water level of waterloggingregion and water level of drainage area. Based on ArcGIS technique, inundateddepth is calculated and reclassified in different grades, the inundated area withthe corresponding level accounts for the proportion of total area, which are usedas a weight, to calculate the crops vulnerability in typical years. The higher ofinundated depth, the wider of the corresponding submerged area, the larger ofvulnerability of hazard bearing body.(4) Analysis of the causes of the waterlogging mechanism. Based onthe regional disaster system theory, the size of the disaster loss iscalculated by the view of the stability of hazard inducing environment, therisk of disaster-causing factor and the vulnerability of hazard bearing body.This paper considers that, the causes of waterlogging mechanism can begeneralized as "mutations of elements in hazard inducing environment-formation of disaster-causing factor-going beyond the waterloggingresistance of hazard bearing body–waterlogging disaster", a coupledprocess of double impacts of the precipitation variation and the high waterlevel of drainage area.