Topographical Critical Model of Loess Gully Head and Its Parameter Determination in Different Land Use Contexts
Gully erosion is a primary form of land degradation in the Loess Plateau region.There is a certain topographic criticality to the occurrence of loess gully erosion at gully head.S-A(Slope-Area)critical model is a common method for simulating and predicting gully head development;however,the insufficient understanding in the spatial differentiation of the model parameters and improper parameter determining in different land use contexts inhibited the model from extensive application.In this study,Unmanned Aerial Vehicle(UAV)photography combined with field survey was used to investigate the Chabagou valley,a typical loess hilly area in northern Shaanxi,China for examination of S-A critical model regarding the spatial differentiation of the model parameters and parameter determination in different land use contexts.(1)The slope gradients at gully heads increased from upstream to downstream,while the drainage area of gully heads showed a decreasing trend.(2)As the S-A critical model for the Chabagou valley,critical constant a were 1.006,1.128,and 1.157 at gully heads in the upstream,midstream,and downstream of the valley,respectively,and correspondingly model exponent b were 0.197,0.203,and 0.209,respectively.It was noticeable that both critical constant a and model exponent b values did not vary to a great extent,exhibiting a slight increasing trend from upstream to downstream,without significant spatial differentiation in model parameters at gully heads.(3)S-A critical model parameters for gully heads was subject to land use types.It had 0.810,2.007 for a and b in sloping farmland,respectively,and 0.159 and 0.341 for a and b in forest-grass land,respectively.The critical constant a for forest-grass land was nearly 2.5 times higher than that of sloping farmland,while the exponent b was nearly 2 times higher that of sloping cropland.This study deepens the understanding of the topographic critical conditions for the occurrence of gully erosion in loess hilly gullies,and enhances the availability of S-A critical model in loess erosion management practice,and would effectively support the precise management of erosion on the Loess Plateau.
NETL
NSTL
万方数据
