Extraction Of Landslide Information And The Hazard Evaluation Of Landslide Using Remote Sensing

Debris flow takes place in the disaster-hit area and become more frequent and wide after the"5.12"WenChuan earthquake in Sichuan province, which thus resulted in great damage to people's life and property. Source of loose earth of Debris flow is one of the basic conditions for occurrence of Debris flow and also one of the main foundation for the forecast of Debris flow. Landslide is one of the main source of the material of debris flow in debris flow catchment area. So it is import to carry out the research of the development feature and the law of distribution of the Landslide in debris flow .catchment area.In this paper, in order to accurately study the development feature and the law of the distribution of Landslide , Four debris flow catchment area which are in the Jushui Town of Anxian County and Zhenping Town of Songpan County are selected respectively as the study area.The landslide and the Vegetation information are extracted using the Aerial Image and the IRS-P5 remote sensing Image in the study area. Based on the methods of spatial analysis of GIS and the method of information value, with six landslide evaluation factors including elevation, slope ,aspect, Vegetation cover land type ,gully density, topographic wetness index, This paper made the hazard assessment and evaluation of the Landslide in the study area. The key conclusions are as the follows:1,It reveals the development feature of the landslide in the study area, using the raster number of various landslide evaluation factors and the raster number of landslide in various landslide evaluation factors using Arcgis(1)Elevation range which the landslide is more likely to occur (less than elevations of 1000m in section of Anxian county study area and less than elevations of 2900m in section of SongPan county study area)is relatively high intensity of human activity area. Therefore, the relationship between Elevation factor and the deformation of landslide stability is reflected by the human activities, rainfall in study area;(2) Slope range which the landslide is more likely to occur. ( more than slope of 40°in Section of Anxian county study area ,slope of 20°-30°in Section of SongPan county study area) showed that the larger the Slope is ,the more the landslide is likely to occur in the study area .In fact , Slope which landslide is more likely to occur is in a certain context.(3)Vegetation types that cover the land in the study area which the landslide is more likely to occur (bare land in section of Anxian county study area ,bare land in section of SongPan county study area)show that the smaller the vegetation cover ,the greater occurrence possibility of the landslide is. Vegetation is helpful to slow down the flow speed and infiltration rate of slope surface flow and make the bank-slope more stable(4)Gully density range which the landslide is more likely to occur (gully density of 5-7 km/km2 in section of Anxian county study area, gully density of 5-7 km/km2 in section of SongPan county study area)shows that the hydrogeological process of the abrupt slope has the adverse effection to abrupt slope stability. Because the flow Erode and undercut slope foot when rainfall flow along the valley. but it is not the larger gully density the greater the likelihood of occurrence of landslide, because If the gully density is too large, the slope often become the product of soil erosion processes instead of the landslide.The elevation of the landslide hazard results corresponds to the distribution of the landslide using GIS. The High risk and Extremely high risk area contains 79.39% of known landslide in section of Anxian county study area and 76.29% of known landslide in section of SongPan county study area. The ratio of landslide density in Various risk levels areas to the percentage of Various risk levels areas in study area is increased as the increasing of the risk levels, It is an accurate measurement to evaluate the hazard of the landslide.The elevation of landslide hazard results reflects the distribution development characters and the law of distribution of Landslide and also illustrates the reliability of the assessment factors and the evaluation system.This practice shows that the elevation method of the Landslide which is in the debris flow catchment area has very good effect by using GIS, remote sensing technology and the method of information value. The assessment results is objective and practical.