The Evaluation Of The Emergence About Geological Disaster In Dingbian County Based On GIS

In recent years, with the rapid development of social economy and human engineering activities, the geological environment changed in different degree, leads different types and scales of geological disasters, Including landslide, collapse, debris flow, ground subsidence, ground collapse, what threats thesafety of people’s lives and property.This paper relies on the detailed survey of geological hazards in Dingbian County, Shaanxi province. On the basis of field survey and data collection, detailed analysised the distribution and formations of geological hazards in the study area, and in the MAPGIS platform, applied the index method and information method for comparison, obtained the evaluation of geological hazard emergence in the study area, And the results are as follow:(1) throughfield survey, there are 328 geological hazards(risks) in the study area, which are 307 ccollapses(93.60%), 20 landslides(6.10%) and 1 debris flow(0.31%), Geological hazards in the study area are mainly distributed in the area of boam, tableland, gully landform in the southern county, and the terrains are gentle and open in northern county.(2)Combined with field survey and previous experience, select the 7 major factors that geomorphology, rock soil mass types, vegetation cover, rainfall, engineering activity, density of geological hazard amount and scale of geological hazard as the indexs of emergence evaluation. And use the analytic hierarchy process to calculate quantitatively the weight relationship between every evaluation index.(3)When using index method to emergence evaluation, determine the relationship between every evaluation index by weight, and stack the layer properties to derive the geological hazard emergence index of every grid unit by mathematical model of index method. Then get the geological hazard emergence division graph of index method by natural breakpoint method.(4)When using information method to emergence evaluation, calculate the information values of 5 evaluation indexs in 15 states, attribute data to area files of every evaluation index and be stacked to grid unit, derive the information value of every grid unit, and get the geological hazard emergence division graph of informatiom method by natural breakpoint method.(5)Through the comparion between the calculation models and results of index method and information method, due to evaluation factors are based on the principle of AHP and valuation by constructing judgement matrix whose weight relationshiop is determine by experience, the relationship of each factor is artificial and empirical, with stronger subjectivity, intefering the accuracy of the results of the evaluation, and the information method calculate the information value of every factor by sample probability, and then exacting and poccessing the information value from every graph layer, and is a calculation process, this method is less human interference, relatively more objective and reliable. The result that is based on information method accords with practical survey, with more credibility and practical value, and conincide to the distribution charatics of geological hazards, geological environmental conditions and human engineering activities in study area, so it is determined as the final evaluation results.(6)Finally determine that: the high emergence area is 1882.5km2, 27.20% of the total area, including 282 geological hazards, the middle emergence area is 1575.1km2, 22.76% of the total area, including 51 geological hazards, the low emergence area is 1324.6km2, 19.13% of the total area, including 5 geological hazards, the non-emergence area is 2137.8km2, 30.90% of the total area, including 0 geological hazards.