The Role of Subsurface Hydrology in Soil Erosion and Channel Network Development on a Laboratory Hillslope

Abstract

Ephemeral gully erosion is currently considered one of the dominant sources of soil loss from the agricultural landscape. It is assumed to be the result of surface flow concentration with hydraulic properties exceeding a given threshold for channel initiation. In this paper, we devised a laboratory experiment to show how subsurface hydrology impacts channel network development and soil loss. A series of rainfall-nrun-on experiments were conducted on a 9.75-m by 3.66-m laboratory hillslope set under drainage or oversaturation (seepage) condition. Soil loss was monitored by collecting runoff samples and by digitizing the soil surface at regular time intervals using digital photogrammetry. We found that the seepage condition produced erosion rates 2.1 times as high as those measured under drainage condition for a high rainfall+run-on intensity (6.8x10^ m^ s'^) and 1.6 times as high for a low intensity (3.4x10^ m^ s'^). After 1.2 m^ of runoff the soil under seepage condition lost on average 1.9 times more soil than the one under drainage condition. Digital photogrammetry performed well at quantifying elevation changes due to channel network development and suggested that channel erosion rates were doubled for the seepage condition. We also found an effect of rainfall-t-run-on intensity on interrill sediment load, supporting a previously proposed model for interrill erosion relating sediment load to rainfall intensity and to the square root of runoff rate. Finally, elevation change patterns observed during each rainfall+run-on event were found to be more consistent with the simultaneous erosion deposition theory as opposed to the sediment transport capacity concept as a sediment transport mechanism. This study demonstrated that subsurface hydrology might be a controlling factor in the rate of development of ephemeral gullies.

Evaluation of structure from motion for soil microtopography measurement

“…Data collected during a series of rainfall experiments aimed at understanding the role of subsurface hydrology on channel network development (Nouwakpo and Huang, ) were used in this paper for the SfM evaluation. The experiments were conducted on a 9·75 m × 3·66 m soil box (Fig.…”

Characteristics of the surface–subsurface flow generation and sediment yield to the rainfall regime and land-cover by long-term in-situ observation in the red soil region, Southern China

“…8 and 9). This could be partly explained by the high precipitation, the high soil moisture content (Zheng et al, 2000;Nouwakpo and Huang, 2012), the near-surface hydraulic gradient (Zheng et al, 2004), and the subsurface hydrology (Nouwakpo and Huang, 2012), which also promoted surface runoff and an increased sediment yield. Subsurface flow augmented surface soil erosion in the red soil.…”

Initial hydro‐geomorphic development and rill network evolution in an artificial catchment

“…Several studies have attempted to predict the location of erosion rills or gullies based on topographic attributes, assuming constant rainfall and runoff conditions (cf. Nouwakpo and Huang, ). Concepts for critical lengths of overland flow have been introduced by Horton () and extended to thresholds of contributing area (Desmet and Govers, ).…”