Slope threshold for overland flow resistance on sandy soils

Recent research on rill flows recognised that an 18% slope can be used to distinguish between ‘gentle’ and ‘steep’ cases for the detected differences in hydraulic (flow depth velocity) sediment transport variables capacity, actual load). The effects of flow velocity, friction factor capacity their interactions affect process-based erosion modelling. main aim this paper is investigate, first time, how affects overland resistance sandy soils, which are characterised by loose particles readily available transported deposited. Using literature measurements carried out soils both gentle steep slopes, a theoretical equation, based integration power velocity distribution, tested. relationship profile parameter Γ, channel slope, Reynolds Froude number calibrated using characterized wide range conditions distinguishing (5.2%–13.2%) (17.4%–42.3%) conditions. analysis demonstrated that: (1) Γ accurately estimated Equation (15) exponents independent condition; (2) coefficient equal 0.8750 0.8984 condition, respectively; (3) estimations Darcy–Weisbach f (Equation 19) accurate errors less than or ±5% 97.2% cases; (4) law condition (19) with = 0.8750) systematically overestimates value. In conclusion, study allowed recognition, unlimited soil detachment flow, energy dissipation processes estimate affected slope. Highlights A tested data obtained soils. Differences investigated. accurate. slopes slopes.