Surface Deformation Characteristics Of Debris Flow Gully Based On Parameter Optimization Of D-InSAR Technology

Debris flow is a geological disaster caused by rainfall in a short time, heavy snowfall and other geological movements, and mainly happends in the mountains,deep valleys and other steep terrain regions. A series of natural factors(geological movement, torrential rain, etc.) and human factors(logging dig, vegetation destruction,excavation construction, etc.) that cause the unbalanced accumulation are all the main inducing factors of debris flow disasters. Since the outbreak location of debris flow disasters is generally in the valleys and areas where terrain changes sharply, human activity regions are generally not in these areas, but under the plain land scarcity and other limited conditions, the human living areas are forced to choose regions where debris flow occurs frequently, and the outbreak of debris flow is bound to bring unpredictable losses to local people’s life and property. Wudu is located in the Bailong river valley of Gansu province. This basin is one of the four parts of geological disaster-prone areas in our country, and is also the intersection of Tibet Plateau, Loess Plateau and the sichuan basin, featured with strong tectonic activities, a lot of fault,rolling hills and plain land scarcity, which makes local human activities mainly concentrated in the valley mouth or on the top of debris where the terrain is relatively flat. By real-time and effective monitoring aiming at Wudu region’s debris flow area,this paper studies the material change before the debris flow disaster occurs, and then explores the material change’s spatial and temporal distribution.Synthetic aperture radar(In SAR) interference technology, a kind of important means of topographic change monitoring, is gradually developed in recent ten years.Based on that, the differential interference radar measurement(D-In SAR) technology,as a further developed technology, is widely used in In SAR technology. But seen from D-In SAR technology’s application fields, since it will face a serious loss of coherence problems when it comes to complex terrain, D-In SAR technology application in these areas is seriously impacted.In this paper, through an analysis on the role of all the parameters that used in the In SAR calculation, the parameter values are adjusted, and thus parameters’ optimization is realized.This method, to a certain extent, can solve the decorrelation problem in low-coherence area, and broaden the range of application of D-In SAR technology, which can also lay a good foundation for applying this technique to the geographical surroundings where the debris flow is located and the terrain is complex.By using D In SAR technology, adopting ENVI SARscape software platform and Wudu region’s ENVISAT ASAR data, and also based on a large numberof experiments and analysis conducted on the key parameters that affect the quality of coherence, part of the debris flow area’s D- In SAR calculation are performed. Finally the following main research results are obtained:(1) Through the data calculation and contrast analysis, it can be demonstrated that the differential interference radar measurement(D- In SAR) technology can improve the coherence by optimizing parameters and thus can be used as a kind of microwave remote sensing method based on planar observation in low coherence area, which ensure a higher efficiency in making full use of SAR data ‘s strong advantage and potential in geological disaster monitoring.(2) Taking the distribution area proportion of the coherence mean and coherence coefficient as an important evaluation basis on the performance of coherence, each parameter participated are adjusted; and after comparing the results when adopting each adjusted parameter selection, the influence of various parameters on the coherence is analyzed; then it can be found that a proper adjustment of parameters used in D-In SAR calculation can remarkably develop the coherence results; finally by selecting some important sensitive parameters that can reduce loss of coherence, the preliminary parameter optimization model is worked out.(3) By applying the D-In SAR technology to part of the debris flow area in Wudu region, the paper discusses the material change law of debris flow area, and realizes the inter-validation of different landslide areas.