| The loess Plateau is one of the regions with the most severe soil erosion in the world,and gully is the symbol of soil erosion development to the most serious stage,is an important source of sediment yield on the Loess Plateau.The study of spatial distribution and morphological characteristics of gully on the Loess Plateau at regional scale is an important basis for gully erosion control planning.Starting from the accuracy analysis of gully morphology acquisition method,gn SS-RTK(Global Positioning System-Real-time Carrier phase difference technology)was used to measure gully at the centimeter level in typical loess plateau hilly gully.At the same time,the gully morphology parameters were interpreted based on decimeter uav images and Google Earth sub-meter images.Thus,the accuracy of the gully morphology acquisition method based on the latter two is clarified compared with the actual measurement.Using GIS spatial analysis and statistical method,256 sampling units of small watershed were selected on the Loess Plateau,and the spatial distribution characteristics of gully density,length,width,distance from watershed and land use type on the slope where gully is developed were extracted by visual interpretation to answer the spatial distribution law of regional scale gully on the Loess Plateau.At the same time,in order to clarify the three-dimensional characteristics and relationship of loess gully,a mathematical model of gully length,area and volume was constructed for three typical small watersheds in different erosive regions of the Loess Plateau based on uav mapping results and data terrain analysis method.The results are as follows:(1)Compared with the measured results of GNSS-RTK gullyes,the length,width,circumference and area errors of gullyes obtained by visual interpretation based on decimeter UAV images are small,and the errors of the above four morphological parameters are 1.52%,1.77%,1.53% and 1.26% respectively;Sub-meter Google Earth image can also be used to extract gullyes’ morphological parameters,and the length,width,circumference and area errors of gullyes are 6.21%,8.12%,6.37% and 6.39%,respectively.To answer the spatial distribution and morphology of gullyes at the regional scale,the above two data sources have good applicability,while the acquisition cost of UAV data is high.Therefore,at present,sub-meter Google Earth image is an ideal data source for the study of spatial regularity of gullyes at the regional scale.(2)At present,the average density of gullies on the Loess Plateau is 4.08km/km~2,and the average density of large and small gullies is 1.02km/km~2 and 3.89km/km~2,respectively.The mean length,width and distance from the watershed were 43.53 m,6.30 m and 71.19 m,respectively.Gullies on the Loess Plateau are mainly distributed along the 400 mm equi-rainfall line,especially from Yan ’an and west to Guyuan,and from Yulin and north to Dongsheng.Dachegou distribution is scattered,mainly concentrated in tianshui to Dingxi area.The main body distribution of small gully is basically consistent with the whole gully.At present,gully is mainly distributed on grassland(48.51%),arable land(29.76%)and woodland(17.27%).Most sampling units of gully were distributed in the loess hilly and gully region,where the average gully density was the largest,reaching 2.67 km/km~2.(3)The relationship between the length and volume of wangwu Gully and the area-volume relationship presents obvious power function distribution,and the area-volume relationship has the strongest correlation.It is suggested that V=0.88A1.24(R~2=0.90)should be used as the prediction equation of the area-volume of wangwu Gully.It is suggested that V=3.02A1.14(R~2=0.91)should be used as the prediction equation for the acreage-volume relationship of anjiagou valley.Ge Tuo Dian gully area-volume correlation is strong power function,corresponding to R~2=0.94,it is suggested that V=1.04A1.16(R~2=0.94)as the prediction equation of gully area-volume. |
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