Abstract
Abstract. This study examines the rainfall-induced change in soil microroughness of a bare smooth soil surface in an agricultural field. The majority of soil microroughness studies have focused on surface roughness on the order of ∼ 5–50 mm and have reported a decay of soil surface roughness with rainfall. However, there is quantitative evidence from a few studies suggesting that surfaces with microroughness less than 5 mm may undergo an increase in roughness when subject to rainfall action. The focus herein is on initial microroughness length scales on the order of 2 mm, a low roughness condition observed seasonally in some landscapes under bare conditions and chosen to systematically examine the increasing roughness phenomenon. Three rainfall intensities of 30, 60, and 75 mm h−1 are applied to a smoothened bed surface in a field plot via a rainfall simulator. Soil surface microroughness is recorded via a surface-profile laser scanner. Several indices are utilized to quantify the soil surface microroughness, namely the random roughness (RR) index, the crossover length, the variance scale from the Markov–Gaussian model, and the limiting difference. Findings show a consistent increase in roughness under the action of rainfall, with an overall agreement between all indices in terms of trend and magnitude. Although this study is limited to a narrow range of rainfall and soil conditions, the results suggest that the outcome of the interaction between rainfall and a soil surface can be different for smooth and rough surfaces and thus warrant the need for a better understanding of this interaction.
Highlights
IntroductionThere are three distinct classes of microtopography surface roughness (Fig. 1a) for agricultural landscapes, each one of them depicting a representative length scale (Römkens and Wang, 1986; Potter, 1990)
Soil surface roughness influences many hydrologic processes such as flow partitioning between runoff and infiltration, flow unsteadiness, and soil mobilization and redeposition on scales ranging from a few millimeters to hillslope level (e.g., Huang and Bradford, 1990; Magunda et al, 1997; Zhang et al, 2014).There are three distinct classes of microtopography surface roughness (Fig. 1a) for agricultural landscapes, each one of them depicting a representative length scale (Römkens and Wang, 1986; Potter, 1990)
The final random roughness (RR) values after the last rainfall succession were selected for being the more closely comparable to the steady-state conditions examined. Both Vázquez et al (2008) and Zheng et al (2014) recorded an increase in RR with rainfall, they had significantly lower values of the RR ratio than the present study. This could be due to several factors including, but not limited to, lower applied rainfall intensity and amount, the initial surface microroughness, and different soil conditions
Summary
There are three distinct classes of microtopography surface roughness (Fig. 1a) for agricultural landscapes, each one of them depicting a representative length scale (Römkens and Wang, 1986; Potter, 1990). The second class consists of variations due to soil clods ranging between 2 and 100 mm. The third class of soil surface roughness is systematic elevation differences due to tillage, referred to as oriented roughness (OR), ranging between 100 and 300 mm. From those outlined above, the first two classes are the so-called random roughness (RR), and constitute the main focus of the present research.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
