Shuitu Baochi Xuebao (Apr 2024)
An Experimental Study on Effects of Rainfall, Inflow and Slope Gradient on Ephemeral Gully Slope Erosion in Chinese Mollisol Region
Abstract
[Objective] In order to investigate the effects of rainfall intensity, inflow rate and slope gradient on hillslope ephemeral gully erosion and implement precise soil and water conservation measures. [Methods] This research established two rainfall intensities (50 and 100 mm/h) and two slope gradients (3° and 7°), and five inflow rates under four combinations of two rainfall intensities and two slope gradients to assess the influences of rainfall intensity, inflow rate, slope gradient and their interaction on slope soil erosion with ephemeral gully, and to quantify the contribution of ephemeral gully erosion to slope erosion. [Results] (1) The impact of slope gradient and inflow rate on slope soil erosion was greater than that of rainfall intensity. Under the five inflow rates, when the rainfall intensity increased from 50 mm/h to 100 mm/h, the slope erosion on the slopes of 3° and 7° increased by 52.3%～81.8% and 29.4%～88.4%, respectively; when the slope gradient increased from 3° to 7°, the slope erosion increased by 114.3%～395.5% and 130.0%～320.9%, respectively; when the inflow rate increased from 15 L/min to 75 L/min, the slope erosion increased by 4.6～13.5 times. The increase of inflow rate aggravated slope gradient influence on slope erosion while weakened rainfall intensity impacts on slope erosion. (2) The combined effects of rainfall intensity, inflow rate, and slope gradient, and inflow rate-slope gradient interactions on slope erosion were the larger impact, followed by the rainfall intensity-inflow rate interaction, and the interplay between rainfall intensity and slope gradient had the lowest impact. Ephemeral gully erosion accounted for over 85% of total slope erosion under various experimental conditions, which increased with inflow rate and slope gradient. (4) The slope erosion rates a positive correlation existed with the flow velocity, shear stress and stream power. Conversely, a negative correlation was observed with the friction coefficient. Among the parameters, the correlation between slope erosion rate and stream power was best. [Conclusion] The research results provide a scientific basis for the development of ephemeral gully erosion prediction model, the separation of ephemeral gully erosion contribution and the study of ephemeral gully erosion mechanism based on erosion dynamic factors and topographic factors and their interaction.
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