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Testing a theoretical resistance law for overland flow on a stony hillslope
Author(s) -
Nicosia Alessio,
Di Stefano Costanza,
Pampalone Vincenzo,
Palmeri Vincenzo,
Ferro Vito,
Nearing Mark A.
Publication year - 2020
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.13709
Subject(s) - froude number , surface runoff , flow (mathematics) , flow velocity , laminar flow , environmental science , intensity (physics) , hydrology (agriculture) , open channel flow , geology , rill , darcy–weisbach equation , soil science , mechanics , geotechnical engineering , soil water , physics , ecology , porous medium , quantum mechanics , porosity , biology
Abstract Overland flow, sediments, and nutrients transported in runoff are important processes involved in soil erosion and water pollution. Modelling transport of sediments and chemicals requires accurate estimates of hydraulic resistance, which is one of the key variables characterizing runoff water depth and velocity. In this paper, a new theoretical power–velocity profile, originally deduced neglecting the impact effect of rainfall, was initially modified for taking into account the effect of rainfall intensity. Then a theoretical flow resistance law was obtained by integration of the new flow velocity distribution. This flow resistance law was tested using field measurements by Nearing for the condition of overland flow under simulated rainfall. Measurements of the Darcy–Weisbach friction factor, corresponding to flow Reynolds number ranging from 48 to 194, were obtained for simulated rainfall with two different rainfall intensity values (59 and 178 mm hr −1 ). The database, including measurements of flow velocity, water depth, cross‐sectional area, wetted perimeter, and bed slope, allowed for calibration of the relationship between the velocity profile parameter Γ, the slope steepness s, and the flow Froude number F , taking also into account the influence of rainfall intensity i . Results yielded the following conclusions: (a) The proposed theoretical flow resistance equation accurately estimated the Darcy–Weisbach friction factor for overland flow under simulated rainfall, (b) the flow resistance increased with rainfall intensity for laminar overland flow, and (c) the mean flow velocity was quasi‐independent of the slope gradient.