Low-Altitude Digital Photogrammetry Technique to Assess Ephemeral Gully Erosion

Recent development in digital imaging makes it feasible to employ photogrammetry procedures to delineate landscape and erosion features. We evaluated the feasibility of using low-altitude photogrammetry to assess ephemeral gully erosion at agricultural fields. We tested an unmanned aerial vehicle (UAV) and a ground based technology to acquire low-altitude surface images to create digital elevation models (DEMs). Collaborators at Wuhan and Yangling in China also used the LIDAR technology on a steep slope for DEM acquisition. We found (1) current DEMs derived from airplane flights are not accurate enough to delineate ephemeral gully channels; (2) a ground-based LIDAR system is capable of generating an accurate DEM and gully channels at steep hillslopes; and (3) at gentle slope situations, low altitude photogrammetry has the potential for acquiring DEMs. Nevertheless, proper deployment of a camera at a suitable height to have sufficient aerial coverage while maintaining the resolution at the Z (elevation) scale to assess rill ephemeral gully development is still a challenge.