Development Mechanism Of Gully In Hilly Loess Region Of Western Shanxi Based On Multisource Remote Sensing

Gully erosion is the main source of soil erosion in catchment on the Loess Plateau.Research on its development model,erosion form and prediction model s is an important basis for revealing the development mechanism of gully erosion and controlling gully erosion.The hilly loess region of western Shanxi is one of the regions with the most serious soil erosion in the Loess Plateau.But the development mechanism of gully erosion still needs further in-depth study.Based on multi-temporal remote sensing satellite images,aviation and low altitude unmanned aerial vehicle（UAV）remote sensing images,this paper was carried out Zhuanyaogou and Zhongduo catchment and analyzes the temporal and spatial changes of gully erosion in the past 50 years.At the same time,precipitation,topography,land use,vegetation coverage,geological conditions,soil texture and other data of corresponding time phase were used to analyze the influencing factor of gully erosion by using geographic detector.Finally,the geomorphic threshold model and the gully erosion rate model were constructed.The main research results are as follows:（1）In terms of morphological characteristics,compared with the Loess Plateau-gully region represented by Zhongduo catchment,the gully erosion in the hilly-gully loess region of western Shanxi represented by Zhuanyaogou catchment is more slender,with higher erosion and more fragmented surface.In terms of interdecadal variation,gully erosion in the study area is still ongoing,gully headcut retreat and gully wall erosion were widespread.The average rate of gully headcut retreat in the two basins is about 0.2m/a,but the areal headcut retreat rates in Zhuanyaogou catchment is significantly lower than that in Zhongduo catchment,because the headcut erosion in Zhongduo catchment is relatively wider.The areal headcut retreat rates in Zhuanyaogou catchment showed a gradual increasing trend.Due to the difference of precipitation,there are differences in the interannual volume changes of the branches in the two basins.（2）The regression relationship between gully volume and length,area shows that area A can better represent the volume.The gully volume estimation models of Zhuanyaogou and Zhongduo catchment constructed by this method are V=0.03A^1.65（R²=0.75）and V=0.39A^1.03（R²=0.70）,respectively.The b value of Zhongduo Basin is closer to 1,and the gully depth is basically constant on the longitudinal profile,while the gully depth of Zhuanyaogou catchment has different growth rates.（3）In the interdecadal variations,The results of the analysis of the influencing factors of gully variations indicate that the main factors affecting the dynamic change of gully erosion in hilly loess region of western Shanxi are the change of land use and vegetation coverage.For the Zhuanyaogou catchment,the main influencing factors from1987 to 2008 were land use change,which was mainly reflected in the conversion from grassland to woodland.The main influencing factors from 2008 to 2019 were FVC change.The decrease of vegetation coverage accelerated the gully erosion rate in Zhuanyaogou catchment.Based on the influencing factors of trenching change in Zhuanyaogou The dominant factor for gully erosion change in the Zhongduo catchment from 1987 to 2021was the change in land use patterns.The conversion of large areas of cultivated land to planting gardens had a significant impact on gully erosion.（4）Based on the geomorphic threshold model between gully head slope S-catchment area A,the critical topographic conditions for gully erosion can be predicted.The geomorphic threshold model of the Zhuanyaogou and Zhongduo catchment are S≥0.545A^-0.24 and S≥1.414A^-0.228,respectively.Compared to the Zhongduo small catchment,the gully erosion in Zhuanyaogou small watershed is generally lower in the S-A double logarithmic coordinate.Under the same gully head slope,the gully erosion in the Zhuanyaogou small watershed is relatively prone to occur.Comparing the constants a and b of the two models,it is found that the catchment area of the Zhuanyaogou small watershed has a greater weight when gully erosion occurs,and the gully erosion of the Zhongduo small watershed is relatively difficult to occur.The results show that this study can be used as an empirical model for predicting the occurrence of gully erosion in hilly loess region of western Shanxi,as verified by the slope and catchment area of branch gulliy head.The gully erosion rate model based on catchment area and annual storm rainfall in hilly loess region of western Shanxi is:R_a=0.004A^0.177P^1.751.