High‐Resolution Measurement of Topographic Changes in Agricultural Soils

Abstract

Terrestrial lidar technology provides accurate surface data at high spatial resolution. This study examined the ability of lidar scanners to evaluate soil erosion and deposition at high spatial and temporal resolutions. Lidar scans were conducted in six field plots with three different tillage systems during two rain seasons, focusing on four major rainfall events. Results show that the lidar scanner identifies changes in the surface elevation in the case of rill erosion within the furrows. In these cases, the high-quality quantitative data can assist practical decision-making and can contribute to the calibration of physically based erosion models. In other cases, however, the results show that the ability of the lidar scanners to detect erosion and deposition processes is limited. The reasons for this limitation are the minor effect of sheet erosion on flat surfaces and soil swelling and shrinking occurring during and after rainfall events. Swelling-shrinking and soil compaction processes need to be taken into account during lidar scanning, as their magnitude is comparable to that of soil loss by erosion. On the other hand, the ability to measure these processes allows investigation of the dynamics of surface processes during wetting and drying sequences. The results showed also that the effect of the rainfall pattern was stronger when the rainfall intensity and the initial soil moisture were higher, and that rill erosion is more important when the furrows are parallel to the slope direction, while deposition is accentuated when the furrows are perpendicular to the slope.

Modeling Soil Erosion With Evolving Rills on Hillslopes

“…At the hillslope scale, soil erosion by overland flow usually generates complex rill networks (e.g., Berger et al, 2010; Bennett et al, 2015; Brunton & Bryan, 2000; Favis‐Mortlock, 1998; Favis‐Mortlock et al, 2000; Hofer et al, 2012; Moreno‐de las Heras et al, 2010). The characteristics of rill network vary remarkably with space and time and have great impacts on flow and sediment routing and soil erosion processes (Brunton & Bryan, 2000; Gumiere et al, 2009; Mancilla et al, 2005; Robichaud et al, 2010), which in turn affect the geomorphology of rill network (Oz et al, 2017; Shen et al, 2015; Wu et al, 2018). This means that soil erosion and rill evolution create a feedback loop where each part of the system responds to changes of other parts.…”

Modeling Rainfall‐Runoff and Soil Erosion Processes on Hillslopes With Complex Rill Network Planform

“…As an essential element of hillslope geomorphology, the characteristics of rill network planform, particularly the local number of rills (the number of rills at a certain cross section, representing the local rill density) and rill orientation angle (an average angle between directions of a rill at measurement points and the vertical direction of the rill), have remarkable impacts on flow and sediment routing from the interrill areas to the rills and on the local rill length, width, and slope gradient (Oz et al, ; Shen et al, ). However, most previous studies only account for the effects of rainfall intensity, soil characteristics, slope length, steepness, vegetation, and soil sealing (Assouline & Ben‐Hur, ; Chen et al, ; Huang, ; Jomaa et al, ; Jouquet et al, ; Robichaud et al, ; Tromp‐van Meerveld et al, ; Wu et al, ; X. Zhang et al, ) and largely ignore the impacts of rill network planform, especially in modeling studies.…”

“…For a planar hillslope, the excess rainfall and sediment generated from upstream interrill areas can be delivered downslope into rills where the overland flow comes across a rill. For a concave hillslope, the excess rainfall from the interrill areas can be delivered into the rills not only from the upstream but also laterally from two sides (Bennett et al, ; Gordon et al, ; Oz et al, ; Schneider et al, ). The effects of rill orientation angle are twofold.…”

Erosion and Lateral Surface Processes

“…Two relatively new methods, with great potential for improving our understanding of erosion processes and measuring capabilities of erosion rates, are the use of terrestrial lidar and rare earth element tracers. Oz et al (2017) present the results of a study conducted in northern Israel on the potential for using lidar to monitor soil loss on agricultural plots after rainfall events. In recent decades, the cost of establishing long‐term erosion monitoring plots has become prohibitive in many parts of the world.…”