Response Of Debris Flow Disaster To Landuse Patterns In The Upper Reaches Of Min River

The upper reaches of the Min River is a fragile region of mountainous environment, and also a more tectonic activity region in our country.After the strong Wenchuan Earthquake in 2008, the debris flow disaster under heavy rainfall became very development, which was in September 2008, August 2010, July 2013, the outbreak of debris flow brought heavy loss. In the three basic formation conditions of debris flow, landuse is a human economic activity with a natural choice, it does not lead directly to debris flow disaster, but indirectly affects bulk material into the channel. Therefore, the reasonable landuse mode can be used to reduce the supply of loose material in the ditch, and unreasonable landuse will accelerate the formation of debris flow.On the basis of previous research results, the paper selected 2005(TM), 2009(TM), 2013(OLI) multi-band remote sensing image map as the basis of research data. With all kinds of tools from ENVI4.8 software, the supervised classification method was uesd on different periods of remote sensing images for interpretation, the upper reaches of Min River is divided into: arable land, forest and grass, bare land, urban and rural construction land, glaciers, waters, and landuse type overall classification accuracy is 97.05%, the kappa coefficient is 0.9644, and it means a good classification result evaluation. Then the landuse type raster data was imported into Arc GIS10.1 software for the effective management of spatial database.the pixel size of DEM map is 8.5 meters by 8.5 meters, the data will be further consolidation, screening, vectorization, the paper delimits the boundaries of debris flow gully, debris flow basin. The number of statistics to the upper reaches of the Min River is 241 debris flow. Among them, Wenchuan County 30, Maoxian 60, Lixian 33, Heishui County 44, Songpan County 73, Dujiangyan Hongkou Township 1(not including 3 townships, 4 townships in Songpan county and Maoxian). In the data collected, the paper summarizes the debris flow characteristics of provenance area, mainly in geological disasters, channel source, slope erosion provenance. It also Summarizes the debris flow mechanism: one is the surface runoff on the slope, which causes stranded sliding surface and material front down transporting into the trench to debris flow, the other one is runoff as the "fire hose" locating in the upper reaches of the steep bedrock basin, leading to rapid concentration of water, strong erosion of the landslide accumulation in the ditch, and the formation of the channel solid material and debris flow.The paper selected Lixian Haermu Gully, Heishui County Seergu Gully Wenchuan County Qipan Gully as typical debris flow. the loose material accumulations of debris flow is simplified as the data surface to replace area of debris flow source volume. In Arc GIS10.1, the source surface raster data, the different periods of landuse types raster data, slope, and DEM data was loaded into the overlay analysis, it can obtain the conditions under the different factors of debris flow distribution in different years. The analysis shows that the debris flow trench near fault zone, obtains seismic energy, and damage caused by the slopes of surface of debris flow gully is not affected by the difference of landuse patterns of the surface, as long as it is advantageous to geological hazards, forest(grass), cultivated land, bare land, land for urban and rural construction, glaciers and other types of land can provide the material source for debris flow. Away from the fault zone, the seismic energy could not hold the dominant. The cultivated land, forest and grass, bare land, urban and rural construction land in different channel, promotes the different extent of formation of debris flow. Within the strong human engineering activities channel, bare land, urban and rural construction land produces the loose matter more. In the vegetation development of debris flow gully, forest(grass), cultivated land produces loose material more.The analysis on the basis of previous research results, An improved model is introduced to research the relationship between landuse types and debris flow, and the sensitivity value of landuse types to debris flow was systematically calculated in the background of the influence of different factors. Compared with the traditional calculation model, the analysis result based on the proposed model is in conformity with that of field survey, showing the most vulnerable landuse types to debris flow are the forest, bare land, urban and rural construction land, when the slope is found in 25 ° ~ 45 °, meanwhile, the area within the strata of Quaternary, Silurian, Devonian, the sensitivity values great in farmland, urban and rural construction land.In this paper, a quantitative analysis method for the active intensity of debris flow disaster is proposed. The source surface of debris flow is replaced by the centroid of the elements. The tool "Near" from Arc GIS10.1 can calculate the distance between a source centroid and the channel. The statistical analysis showed that before the earthquake in 2005, source centroid distance of the channel is far, in 2009, 2013 source centroid distance of the channel is near, debris flow in the aftermath of the earthquake increased activities.