Risk Evaluation And Simulation Of The Potential Collapsing Hills In Fujian Typical Collapsed Area

Changting and Anxi County are typical collapsing area in Fujian Province.The majority of former research focused on the study about spatial distribution,erosion mechanism and soil characteristics after collapsing hill’s occurring,and there are few study about the simulation of potential collapsing hill.In this article,filed survey,data collection and laboratory analysis were used to screen the data source, which the risk assessment factors based on.The assessment factors of watershed in Changting and Anxi County including topography,precipitation and hydrology were extracted and analysed in ArcGIS and SPSS.Use the spatial relationship between the collapsing hill and factors to simulate the distribution of the potential collapsing hill in watershed.The main results were as follows:(1)Both the surface roughness and surface length of the watershed would decrease with the increase of the resolution,and showed inflection points at specific resolution, which was the optimal resolution of the scale.After comparison and analysis, the the optimal resolution of 1:10,000,1:50,000,1:100,000 and 1:250,000 DEM of watershed in Changting were 4m.8m.8m and 16m respectively.and the optimal resolution of the 1:10,000,1:50,000,1:100,000 and 1:250,000 DEM of watershed in Anxi were 8m,8m,16m and 16m.(2)The collapsing hill in Changting watershed mainly distributed in the 5°-25° slope and southwest slope of adret.All of the collapsing hill distributed in the 250-500m high hills,whose relative elevation range 20-50m,the major basin level were 3 and 4,waterhed’s rainfall was about 1640mm.While The collapsing hill in Anxi watershed mainly distributed in the10°-25° slope and southwest slope of adret.All of the collapsing hill distributed in the 100-500m hills,whose relative elevation range 0-100m,the major basin level were 3 and 4,waterhed’s rainfall was about 1600mm.(3)The risk level of potential collapsing hill in NO.5 basin was divided to 6 levels.In the basin,potential collapsing hill mainly distributed in the level range 3-5,whose area was 47.42km2 accouting for 86.71% of total area,the area of level 2 and 6 are less,only 3.01 and 4.14km2,and there were few area of level 1.NO.10 basin had 125 collapsing hill oringinally.among which 84 of them distributed in the region of risk level 4 and 5 accouting for 67.2% of total collapsing.The result of prediction is tolerable with further improving.