| The terrain of the loess hilly and gully area in northern Shaanxi is undulating and broken,and there are extensive gullies in the area.The severe gully not only hinders land use and economic development,but also brings a series of ecological and environmental problems to the Lower Yellow River.Research on the occurrence and development mechanism of gully is of great significance to the prevention and control of soil erosion.This paper takes multiple small watersheds in Wuqi County in the loess hilly region of northern Shaanxi as the research object.Based on remote sensing image(0.5 m)obtained by Pleiades satellite and 1:10,000 DEM,morphological parameter of ephemeral gullies and permanent gullies in the watershed are extracted through visual interpretation.Analyze of the morphological characteristics of gullies in the study area and the degree of erosion in each watershed.Taking the head of the gully as its spatial location mark point,the spatial distribution characteristics and spatial distribution aggregation of the gullies in each watershed were analyzed using the method of spatial analysis.Finally,analyze the influence of land use types and topographical factors on the spatial differentiation of gullies,and the influence of upslope ephemeral gullies on the development of permanent gullies is explored through correlation analysis.The research results can provide theoretical basis and reference for the understanding of erosion process and the prevention and management of gully in the Loess Plateau.The main research conclusions are as follows:(1)The morphology of gullies in the study area is quite different.Based on the gully density in this study area,the erosion degree classification standard is constructed.The gully density of 50%of the watershed in the study area is 8-15km/km~2,and the urgency of erosion control is low.The gully density of 47%of the watershed is 16-23 km/km~2,the surface fragmentation is relatively large,and the urgency of governance is secondary.The erosion intensity in the area with density of 24-31km/km~2 is relatively high,and it is urgently needed to be treated.(2)The heads of the gullies are mainly on the slope of 15°-35°,and they are concentrated on the semi-sun slope.Gullies in 97%of the watershed are distributed in clusters,and most of them are ephemeral gullies on the upslope and permanent gullies on the downslope.The aggregation of gully in cultivated land watersheds is stronger,grassland watersheds is second,and woodland watersheds are the worst.(3)The degree of erosion in grassland watershed is greater than that of cultivated land and woodland.The morphological characteristics of gully slope differentiation law is mainly that the length of ephemeral gully,the length of permanent gully,and the area of gully increase first and then decrease with the increase of slope.The maximum ditch length is 25°-35°,and the maximum gully area appear in 25°-45°.The width of the gully increases with the increase of the slope,and the law of differentiation in the slope direction is not significant.The morphological characteristics of other gullies are characterized by the highest degree of development of semi-sun slopes.The gully density increases with the increase of the slope,and then begins to decrease after exceeding the critical slope.The gullies in each watershed are mainly distributed at 15°-45°.The differentiation law of gully density in the slope direction is that the permanent gully mainly develops on the sunny slope and the semi-sun slope,while the ephemeral gully can be formed on the shade slope and the sunny slope.There are fewer gullies on the northeast and south slopes in cultivated watersheds and grassland watersheds,and there are fewer gullies on the south and southwest slopes in forestland watersheds.There is a correlation between the ephemeral gully spacing and the permanent gully density.The formation of ephemeral gully will change the slope runoff and further accelerate the formation of permanent gully. |
PDF Full Text Request