Effects of rock fragment cover on hydrological processes under rainfall simulation in a semi‐arid region of China

Abstract

Rock fragment cover has long been an important agricultural crop production technique on the Loess Plateau, China. Although this approach plays an important role in controlling hydrological processes and preventing soil erosion, inconsistent results have been recovered in this field. In this study, we investigated the effects of rock fragment cover on infiltration, run‐off, soil erosion, and hydraulic parameters using rainfall simulation in the field in a semi‐arid region of China. Two field plots encompassing 6 rock fragment coverages (0%, 10%, 20%, 25%, 30%, and 40%), as well as 2 rock fragment positions and sizes were exposed to rainfall at a particular intensity (60 mm h−1). The results of this study showed that increasing the rock fragment coverage with rock fragments resting on the soil surface increased infiltration but decreased run‐off generation and sediment yield. A contrasting result was found, however, when rock fragments were partially embedded into the soil surface; in this case, a positive relationship between rock fragment coverage and run‐off rate as well as a nonmonotonic relationship with respect to soil loss rate was recovered. The size of rock fragments also exerted a positive effect on run‐off generation and sediment yield but had a negative effect on infiltration. At the same time, both mean flow velocity and Froude number decreased with increasing rock fragment coverage regardless of rock fragment position and size, whereas both Manning roughness and Darcy–Weisbach friction factor were positively correlated. Results show that stream power is the most sensitive hydraulic parameter affecting soil loss. Combined with variance analysis, we concluded that the order of significance of rock fragment cover variables was position followed by coverage and then size. We also quantitatively incorporated the effects of rock fragment cover on soil loss via the C and K factors in the Revised Universal Soil Loss Equation. Overall, this study will enable the development of more accurate modelling approaches and lead to a better understanding of hydrological processes under rock fragment cover conditions.

Impacts of Filled Check Dams with Different Deployment Strategies on the Flood and Sediment Transport Processes in a Loess Plateau Catchment

“…The calibrated Manning's roughness coefficient values were small but reasonable due to the low vegetation coverage and the large area of bare land and cultivated land in the Shejiagou catchment during the simulation period (i.e., 1964) [25,27]. Similar values have been measured on bare land and cultivated land through field experiments in the Loess Plateau in a few studies e.g., [51,52].…”

Numerical modelling shows an old check‐dam still attenuates flooding and sediment transport

“…The calibrated Manning's roughness coefficient (n) values were small but reasonable due to the low vegetation coverage and the large area of bare land and cultivated land in the Shejiagou catchment during the simulation period (i.e., 1964) (Fang et al, 2011;Zhang et al, 2016). Similar values have been measured on bare land and cultivated land through field experiments in the Loess Plateau in a few studies (e.g., Wu et al, 2017;Xia et al, 2018). For example, Wu et al (2017) developed a sheet erosion equation for typical loess soil by conducting 36 plot experiments (rainfall intensity ranged from 48 to 150 mm h À1 , slopes ranged from 12.33% to 46.63%) and obtained the n-value range of 0.0102 to 0.0620 s m -1/3 .…”

Effects of Content of Soil Rock Fragments on Soil Erodibility in China

“…Simanton and Toy [ 37 ] noted that hillslope morphology influenced rock fragment cover, finding a logarithmic increase of rock fragment cover with slope angle for hillslopes in semiarid range lands of Arizona, USA. Xia [ 38 ] found that rock fragments will be exposed on soil surface because of frequent human activities. Li et al [ 33 ] pointed out that the differences between the spatial patterns of rock fragment and vegetation coverage correlated with land use.…”