A Measurement Method for Rill and Ephemeral Gully Erosion Assessments

Abstract

Core Ideas Photogrammetric techniques for spatiotemporal measure of topographic data Physical data for validation and development of soil erosion modeling technology Automated analysis presentation package Rill and ephemeral gully monitoring at high spatial and temporal resolution When flowing water concentrates on hillslopes, the erosivity of the water may only be limited by the erodibility of the soil. Over time, concentrated flow paths may become permanent drainage channels, and such rills and ephemeral gullies often have negative impacts on crop yield and downstream sedimentation. Spatiotemporal topographic assessments of rill and gully dimensions compliment hydraulic erosion estimates, and they can elucidate soil erosion processes and provide data for model validation. Accurate and detailed topographic assessments, however, can be cost prohibitive. The objectives of this study are to describe and evaluate a topographic assessment method with relatively high spatial and temporal resolution, to discuss its costs and limitations, and to provide an assessment procedure for erosion characterization and data optimization. Three locations are evaluated that are pertinent to soil erosion research on the field, plot, and laboratory scale. In each setting, the sites are monumented and monitored using photogrammetric techniques. Photogrammetry is a simple, robust means to track landscape evolution and morphodynamic changes in rills and ephemeral gullies. The assessment procedure describes study site attributes at a variety of spatial and temporal scales, it is cost‐effective, workforce empowering, and reliable, and the analysis and presentation can be automated. Capturing this type of information is critical to an improved understanding of the fundamental principles necessary to enhance modeling technology to estimate erosion potential at various scales and to assess the efficacy of conservation practices.

Quantifying uncertainty in high-resolution remotely sensed topographic surveys for ephemeral gully channel monitoring

“…2a) and laying out 406 × 406 mm quad-triangle, whiteon-black sheet GCPs and considering the long and short axes of the field as well as the high and low elevations within the field boundary, herein considered to be the field GCPs (10 total). One additional set of GCPs with RAD coded targets was arranged along the gully channel (four pins at the location; Wells et al, 2016), herein considered to be the channel GCPs (four total). All GCPs were surveyed using Topcon GR-3 DGPS survey equipment (Topcon Corporation, Tokyo, Japan; 10 mm of horizontal and 15 mm of vertical kinematic accuracy) to obtain relative position in reference to the state monument point.…”

“…Terrestrial photogrammetry was conducted using a Nikon D7000 16.2 MP camera (Nikon Inc., Melville, NY) with a calibrated 20 mm lens (Gesch et al, 2015;Wells et al, 2016). The camera was mounted to a backpack frame connected to an iPad mini (Apple, Cupertino, CA) through a WiFi CamRanger hub (Camranger LLC; http://www.camranger.com) (Wells et al, 2016).…”

“…Studies involving various surveying techniques of concentrated flow paths have revealed a wide range of quality, accuracy, cost, and field campaign effort (Momm et al, 2011(Momm et al, , 2013bCastillo et al, 2012;Wells et al, 2016). Among the surveying techniques considered, photogrammetry has been shown to provide simple but robust measurements of smallscale changes in geomorphologic characteristics within agricultural fields (Castillo et al, 2012;Gesch et al, 2015;Wells et al, 2016).…”

“…Among the surveying techniques considered, photogrammetry has been shown to provide simple but robust measurements of smallscale changes in geomorphologic characteristics within agricultural fields (Castillo et al, 2012;Gesch et al, 2015;Wells et al, 2016). Further, a wide variety of platforms and techniques have been used to capture images, including kites , backpacks (Wells et al, 2016) and UAVs Bachrach et al, 2012;James and Robson, 2014;Cook, 2017).…”

Erosion processes on different relief units: the relationship of form and process

“…The development of these rills may increase erosion rates to an order of magnitude higher than erosion caused by non-concentrated surface flows (Cerdan et al, 2002;Merz and Bryan, 1993;Nouwakpo et al, 2016b;Poesen, 1987;Wirtz et al, 2012a). Because of their highly erratic appearance and their easy destruction through soil management, erosion processes in rills are difficult to quantify (Casalí et al, 2006;Nouwakpo et al, 2016a;Wells et al, 2016).…”