Research On The Temporal And Spatial Distribution And Influencing Factors Of Geological Hazards In Wenzhou City Based On GIS

Located in the southeast coast, the city of WenZhou is featured by complicated topography resulting in varied geological disasters such as landslides, collapses and mud and rock flow, which caused dramatic losses in local population. Therefore, it becomes crucial figuring out the influencing factors responsible for geological disasters in this area and analyzing them in order to take proper measures accordingly, which holds vital significance for the practice of prevention and reduction of disasters in WenZhou.Through statistical and spatial analysis, we measured the frequency, scale, and severity of damage caused by landslide, collapse, and mud-rock flow in WenZhou since 1990, and also screened and quantified the underlying influencing factors. After that, we performed statistical comparison, regional projection area calculation, grading of slope, and grading of proportions of altitude ranges. We subsequently ruled out the possibilities of occurrence of disasters under varied influencing factors. Accordingly, we attempt to elicit the connection between spatial distribution, the dynamic feature and influencing factors.Administrative areas and counties in the city of WenZhou are set as the basic units of the influencing factors of geological disasters in the analysis process. Basically, WenZhou was divided into a 25*25 grid matrix, which are all subjected to statistical analysis based on every influencing factor. The primary influencing factors of each administrative area or county(grading of terrain slope and grouping of geological structures, 4 groups in all) are picked out. Special analyst in Arc GIS program was employed to calculate the projection area of each grade of plane and each group of formation of the25*25 grid matrix of these regions. Lastly, we did proportional calculation and analysis among the varied slope and different groups as to evaluate the significance of varied slopes, geological structures, and altitudes on different types of geological disasters.Through this work, we obtained imformation on the pattern of the temporal and spatial distribution of major geological disasters (landslide, collapse, mud-rock flow), and relative charts, contributed rain precipitation, slope degree, terrace to be the main influencing factors, and learned the ties between various factors and major disasters by drawing graphs with GIS. Specificically, landslide and its potential hazards range from 25-45 in slope degree, and from 50-500m in altitude(hills); collapse above 45 in slope degree, especially steep slope of above 60; mud and rock flow above 500m altitude. Through analysis of distribution of disasters and influencing factors, we come to the conclusion that for landslide and its hidden risks , the major influencing factor is rain precipitation (may-august)and topography. For collapse and its hidden risks, is residential distribution(human engineering), precipitation and slope degree. And for mud and rock flow , strong precipitation and topography.