Identifying sediment transport capacity of raindrop-impacted overland flow within transport-limited system of interrill erosion processes on steep loess hillslopes of China.

Highlights • Another method was provided to determine T c of raindrop-impacted interrill flow. • T c can be calculated using power function equation of slope gradient and rainfall intensity. • Stream power together with rainfall kinetic energy can best describe T c. Abstract Interrill erosion processes typically involve such scientific issues as detachment-limited and transport-limited erosion behaviour. An accurate estimation of the sediment transport capacity ( T c ) by raindrop-impacted overland flow is critical for interrill erosion modelling and for evaluating sediment budgets under erosion-limiting conditions. Simulated rainfall experiments with rainfall intensities from 0.8 to 2.5 mm min−1 over a three-area soil pan with slope gradients from 12.7% to 46.6% were conducted to identify the transport-limited cases and determine T c by raindrop-impacted overland flow within the transport-limited systems of interrill erosion processes. Results indicated that T c increased as a power function of rainfall intensity and slope gradient ( R2 = 0.84, NSE = 0.75), and T c was more sensitive to rainfall intensity than to slope gradient. In terms of R2 and NSE , stream power was the key hydraulic parameter that influenced T c among flow velocity ( R2 = 0.64, NSE = 0.39), shear stress ( R2 = 0.53, NSE = 0.23), stream power ( R2 = 0.76, NSE = 0.52) and unit stream power ( R2 = 0.49, NSE = 0.16). The addition of rainfall physical parameters in response equations of T c in addition to hydraulic parameter, could improve an accuracy of T c modelling. Stream power combined with rainfall kinetic energy can best describe the T c of raindrop-impacted overland flow within the transport-limited system of interrill erosion processes by a power-exponent function ( R2 = 0.90, NSE = 0.72). Rainfall kinetic energy can reduce the Darcy-Weisbach resistance coefficient of raindrop-impacted overland flow and thus benefit sediment transporting. This study provides another method for directly identifying the T c of raindrop-impacted overland flow in interrill erosion processes on steep loess slopes, and points out that rainfall impacts should be particularly considered when studying T c by raindrop-impacted overland flow. [ABSTRACT FROM AUTHOR]