Study Of Route Selection For Forest Fire Separating Network Based On GIS

Fire is one of the eight natural disasters to the forest resource,which is not only threat the people's lives and property,but also destroy the ecological environment.The forest break route selection was selected by hand and mostly relied on the experience in the past,which made the consequence not objective,efficient and scientific.The effeictive of forest fire break belts in China now are restricted by the lower density and unconnection situation.It's better to enhance the efficient of fireproofing via optimizing the forest break belts route selection and setting an accessibility and reasonable separating network.The article discusses the internal and external profile of route selection,the aim is use the road line selection method,and then combine computer and Geographical information System(GIS)technology for selecting the forest fire barrier belts.The purpose is to make the result more scientific and reasonable,as the same time,provide the theories and method for the following studies.Research area is external rectangle of Daguishan forest farm,the main studies are:Analysis the relationship between forest fire break belts selection and social,economic,environment and safety,etc.Determined surface features,elevation,slop and aspect as four main influence factors.Get forestry experts to rate the four main impact factors and score the factors throuth two two comparetion.Analysis the weight of each selected effective elements based on Analysis Hierarchy Process(AHP).Apply spatial analysis tool to reclassification surface features for six class,they are bare land,water,roads,forest land,construction and farm land.In order to increase reclassification precision up to 85%,we did some post-processing like majority filter,smoothing and remove islet.Reclass the other factors and evaluation the main factors.The sort of surface features is bare land>water>forest>road>farm land>construction which according to the costs of occupancy,construction and recovery,the assignment value is 0,8,16,32,64,100 respectively.The best suitable altitude is 350 m?650 m that between elevation standard deviation and average elevation.The route selection costs will increase if the altitude beyond the suitable range.Reclassification altitude is 28m?168m,168m?287m,287m?350m,350m?650m,650m?834m,834m?990m,990m?1263m,the assignment value is 32,16,4,2,4,8,16 respectively.Slop evaluation based on the costs of construction and maintenance and fire spread speed which increase along with the slop rise.The slop is divided into 8 class as 0?3°,3?6°,6?9°,9?12°,12?16°,16?30°,30?45°,>45°,the assignment value is 1?2?4?8?16?32?64?96.The aspect evaluation is considered about the temperature of combustible substances and fire spread speed in the different aspect.The final order is shady slop>flat slop>halfshady-halfsunny slope>sunny slop,which corresponding the evaluation 1,2,3,5.Then produce single element cost model.Generate the compositive cost model by overlay calculation according to the weight of main factors.Choose the start and final point for route selection line via the season and wind direction of study area,calculate the optimize route according to shortest cost path method,then connect the nature break belts,engineering break belts and biological break belts to a closed forest fire separating network.The article finished setting a forest separating network for study area base on the original biological break belts and the other forest barriers like nature break belts,optimize route,roads and rivers.It basically solves the original biological barrier problems of unconnected,scatter and uneven,also can solves the problem of relief channel unsmooth and help to choose the best rescue plan.The density of biological add to 1.8m/hm2 and the optimize route increase 1.0 m/hm2 at the same time.