Location: National Soil Erosion Research Lab
Title: Low-Altitude Digital Photogrammetry Technique to Assess Ephemeral Gully Erosion Authors
Submitted to: International Geoscience and Remote Sensing Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 26, 2008
Publication Date: N/A
Technical Abstract: Ephemeral gully erosion is the main source of sediment from the agricultural landscape, unfortunately, it has been overlooked in traditional soil erosion assessment. Since an ephemeral gully can be easily alleviated or filled by normal tillage, the difficulty in making the ephemeral gully erosion assessment is the lack of well-defined channel morphology such as classical gullies and river channels. The intermittency of ephemeral gully formation and its easy removal adds to the difficulty in its quantification. In this research, we developed software to extract surface elevation data (DEM) from overlapping digital photographs of the land surface taken at low altitude. We compared photogrammetry with ground-based Light Detection and Ranging (LIDAR) measurements at steep loess hillslopes with distinct ephemeral gullies. We compared the channel network derived from close range DEMs with those visually identified from the photographs. We found the following: 1) the regular topographic DEM is not accurate enough to delineate ephemeral gully channel; 2) ground-based LIDAR system is capable of generating accurate DEM and gully channels at steep hillslopes; and 3) at gentle slope situations, low altitude photogrammetry is most feasible. 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.