Effects Of Land Use Change On Erosion Gully Characteristics In Hehuang Valley

Gully erosion is a concrete manifestation of soil erosion,which leads to intense segmentation of landform,encroachment of land,land degradation and even complete destruction.Land use is an important influencing factor of gully erosion.The study on the influence of land use change on the characteristics of erosion gully is of great significance to regional erosion gully control and land use comprehensive planning.Therefore,this study takes Hehuang Valley,a typical area of the Loess Plateau,as the research object.On the basis of analyzing the spatial-temporal variation characteristics of land use in Hehuang Valley,five typical small watersheds are selected in the north,south,west,east and central parts of Hehuang Valley combined with field investigation and indoor interpretation.The land use and erosion gully of five small watersheds in 2005 and 2020 were extracted by visual interpretation method,and the results of indoor interpretation were verified by field survey and aerial images taken by UAV.The temporal and spatial changes of land use and the variation characteristics of the morphological and quantitative parameters of erosion gully in small watersheds were analyzed.The impacts of different land use patterns on erosion gully changes at small watershed scale and erosion gully catchment scale were investigated,and the following conclusions were obtained:(1)The land use interpretation accuracy of Google Earth images is over 90%,and the average deviation between the area and circumference of erosion gullies is 5.8%-9.8%.The interpretation results are good,suggesting that summer images should be preferred for land use extraction and winter images should be preferred for erosion gullies extraction.(2)Land use in Hehuang Valley increased mainly in grassland from 2000 to 2010,and the increase of grassland mainly occurred in central and southern regions;From 2010 to 2020,land use changes mainly occurred in the central and northern regions of China,and the quantity and spatial changes were related to national and local policies.Land use change in typical small watershed mainly occurred at the junction of different land types or in the area with steep slope.(3)Erosion gully area,total length,average length,average width and average size increases as the series,which is mainly composed of forest land in small watershed,the erosion gully shape parameter distribution is concentrated and values are lower,the more balanced watershed land use type distribution,erosion gully shape parameter distribution is relatively fragmented and higher value.From 2005 to 2020,erosion gully density and fragmentation degree of each small watershed increased.(4)The average width of newly eroded gullies is the largest on unused land,and the average length and circumference of cultivated land are smaller than those of converted forest land.Different land use types and configurations in the catchment area of eroded gullies lead to the difference of new eroded gullies.Erosion gullies mostly occur in the areas with sparse forest land or high altitude,and the cultivated land at high altitude is still prone to erosion gullies.The policy of returning farmland to forest promotes the stability of erosion gully and slows down the development of erosion gully in small watershed.