Upslope inflow, hillslope gradient and rainfall intensity impacts on ephemeral gully erosion

Abstract

Ephemeral gullies (EGs) are major contributors to sediment loss and land degradation on cultivated lands. However, the topography and rainfall impacts on EG development processes are still unclear, especially on steep loessial hillslopes such as the Loess Plateau. A series of laboratory rainfall simulation experiments were conducted to investigate the impacts of topographic characteristics (3 typical slope gradients (S): 26.8%, 36.4%, and 46.6%; and 5 upslope drainage areas (A): 16, 32, 64, 96, and 128 m2) and rainfall intensities (3 representative erosive rainfall intensities 50, 75, and 100 mm hr−1) on EG erosion on a steep loessial hillslope. A large slope adjustable soil pan (8 m‐long, 2 m‐wide, and 0.6 m‐deep) and a side‐sprinkler rainfall simulation system were used in this study. The results showed that soil loss increased when rainfall intensity, slope, and upslope drainage area increased. Upslope topography and inflow had great impacts on downslope EG erosion, and the contribution percentages ranged from 52.2% to 74.1%, from 48.3% to 71.4%, and from 29.5% to 66.7% for the 50, 75, and 100 mm hr−1 rainfall treatments, respectively. Runoff velocities with upslope inflow were 22.7% to 79.4% larger than those without inflow, and the upslope inflow was more effective than rainfall intensity in increasing runoff velocities in EG channels, thus caused more soil erosion. Soil loss equation based on rainfall intensity and AS2 (product of the upslope drainage area and the square of the local slope gradient) was established and validated. The determination coefficient (R2) and Nash–Sutcliffe simulation efficiency (ENS) were 0.80 and 0.87, which showed satisfactory accuracy. This equation can be used to predict the EG erosion in various topographic and rainfall conditions on steep loessial hillslopes.

Rainfall intensity in geomorphology: Challenges and opportunities

“…High-intensity rainfall favours the occurrence of surface runoff and rill cutting (He et al, 2017), but this may also occur from saturation overland flow in events of low intensity but long duration (Kirkbride and Reeves, 1993). Xu et al (2017) found in laboratory experiments on gully erosion in a very large soil box that cumulative gully cutting (expressed in terms of the mass of soil removed) increased with rainfall intensity. In Israel, Hoober et al (2017) identified an intensity threshold for the cutting and modification of ephemeral gullies of 12mm h –1 .…”

Runoff and soil erosion responses to rainfall and vegetation cover under various afforestation management regimes in subtropical montane forest

“…The low data requirement, small number of variables, and extrapolation to the same region increase the applicability of regression models on annual erosion at the slope scale, though the process dynamics are not precisely presented. For example, with the use of regression models, it was concluded that the soil loss is an exponential function of rainfall intensity, upslope drainage area, and slope on the basis of laboratory experiments (Xu, Zheng, Wilson, & Wu, ). Based on observations made at microplots in an arid environment, it was reported that soil erosion is linearly related to rainfall intensity, slope, and antecedent moisture (Ziadat & Taimeh, ).…”

Characteristics of pulsed runoff-erosion events under typical rainstorms in a small watershed on the Loess Plateau of China

“…(2017) and Wu et al . (2017) both found that soil loss increased with increased rainfall intensity 79 , 80 .…”