Rangeland hillslopes provide much of the sediment supplied to channel systems and their lengths exert a fundamental constraint on hillslope diffusive processes.However,information regarding lengths of rangeland hillslopes,and how best to estimate them,is limited.In this study,three groups of watersheds(10 in total)were selected from the Walnut Gulch Experimental Watershed according to their geology,soil and vegetation characteristics.Group 1 watersheds were at lower elevations dominated by shrubs,Group 3 were at high elevations dominated by grass,and Group 2 were mixed shrub and grass.Their hillslope lengths were calculated from 1 m-resolution DEMs using three methods:a flow routing al-gorithm,slope-area relationships,and inverted relationship with drainage density.Parameters that characterize the current watersheds,including Hack's exponent and coefficient,watershed shape coef-ficient,channel concavity and steepness,and surface roughness,were quantified and related to hillslope lengths.Results shows:(1)estimated hillslope lengths were different for the three methods and between the three groups of watersheds;(2)hillslope lengths that measured from the flow routing algorithm for the ten selected watersheds primarily ranged from 30 to 100 m,with a median value of 63.0 m,which was 20％-50％greater than those derived from slope-area plots or drainage densities;(3)hillslope lengths estimated from the flow routing method were greater in Group 3 watersheds than in Group 2 and then in Group 1 watersheds.We attributed these differences in hillslope lengths to the historic epeirogenic pulses,watershed and drainage network morphology,and differences in vegetation char-acteristics;(4)measured hillslope lengths from the flow routing algorithm were best correlated with hillslope relief,then surface roughness,channel steepness and concavity.These results would benefit the applications of hydrological and erosion models in rangelands.

Li Li;Mark A.Nearing;Philip Heilman;Mary H.Nichols;D.P.Guertin;C.J.Williams

School of Natural Resources and the Environment,University of Arizona,Tucson,AZ,85705,USA;USDA-Agricultural Research Service,Southwest Watershed Research Center,Tucson,AZ,85719,USA

国际水土保持研究（英文）

[1]Li Li;Mark A.Nearing;Philip Heilman;Mary H.Nichols;D.P.Guertin;C.J.Williams-.Rangeland hillslope lengths:A case study at the Walnut Gulch Experimental Watershed,southeastern Arizona)[J].国际水土保持研究（英文）,2022(04):597-609

Rangeland,hillslope,Gulch,epeirogenic

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