Research On The Topographic Features' Change Detection Of Debris Flow Gully Using Dems

Debris flow is a kind of chaotic geologic hazard which is familiar in the west mountainous areas of our country. It directly threatens people' s life and production, causes severe soil and water loss and badly destroys natural environment. Among the three forming factors of debris flow, topographic features and loose mass reserves are main factors affecting debris flow' s formation, development and intensity, and researching these factors based on topographic changes is a basic method. The development of Remote Sensing and Photogrammetry technologies offer rich data source and advanced methods to model the earth' s surface for researching geographic phenomena such as debris flow. As a kind of mathematic expression for terrain, Digital Elevation Model (DEM) can provide basic 3-dimension analyzing data. It' s an important supplement to traditional theories and methods of researching debris flow using DEM to monitor the topographic features' change of debris flow gully.Supported by the NSFC project, the Pu Wai debris flow gully located in Pu Xiong (a town situated in middle of the railroad from Cheng Du to Kun Ming), as the study area and different temporal aerial photographs (scale of 1:20000 for 1957;scale of 1:15000 for 1987) as basic data, the method of producing large scale DEMs and contour data (scale of 1:2000 and grid resolution of 2m) is detailedly discussed using the VirtuoZo system, and the technology of surface matching without reference points (Robust Least Z-Difference) is applied to match the tow temporal surface models, and its effect simply analyzed, too. The topographic parameters and evaluating indicators of the study area are extracted using differenttemporal DEMs using the ArcView 3.2a, and changes of the relief features are detected and analyzed by comparison, using average gradient and incision degree as the indicators which indicate the developing situation of the gully bed, and slope as the main indicator of the intensity of the area' s terrain changing. The eroding and depositing distribution can be detected by the elevation difference model which is gained by making difference operation to the tow temporal DEMs, and the loss quantity of the gully' s mass reserves is calculated, thus the rough changes of the gully' s topographic features and mass reserves in 30 years are detected.The applying research not only provides reference for drawing measures and establishes a good foundation for further understanding the law of debris flow, but has significant practical sense and value in accumulating the knowledge of environmental hazards, including phenomena, nature and mechanism, and researching the soil eroding, water and soil preserving, alleviating and defending hazards measures of the west regions of our country.