Using small unmanned aerial systems to evaluate downstream geomorphic impacts from dam removal

Authors: Alexandra Evans*, University of New Hampshire, Scott Greenwood, University of New Hampshire, Kevin Gardner, University of New Hampshire, Denise Burchsted, Keene State College
Topics: Remote Sensing, Environmental Science, Quantitative Methods
Keywords: drone, suas, dam, dam removal, geomorphology, photogrammetry, sfm, remote sensing, uas, river, fluvial, substrate
Session Type: Paper
Day: 4/7/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Jefferson, Marriott, Mezzanine Level
Presentation File: No File Uploaded

Dam removal is an increasingly popular management solution to address ecological impacts of aging dam infrastructure. However, the river ecosystem responses from dam removal are poorly understood due to minimal pre-/post-removal studies (Foley et al. 2017; Hart et al. 2002; Poff & Hart, 2002). In addition, administrative, technical, and financial barriers often prevent sufficient collection of data for restoration project evaluation (Roni & Beechie, 2012; Bernhardt et al. 2005; NRC 1992). This work seeks to develop photogrammetric techniques using small unmanned aerial systems (sUAS, a.k.a. “drones”), to assess geomorphic changes in riverine systems and validate them against conventional techniques. A DJI Phantom 3 Professional sUAS collected imagery downstream of a small dam removal in Dover, NH pre- and post-removal. Geomorphic changes to the reach were evaluated using digital surface models and orthomosaics created using commercially available structure-from-motion photogrammetry software (Agisoft PhotoScan Professional). Changes in topography were identified from the sUAS products and machine learning approaches were used to map substrate types across the study area. For conventional approaches, monumented cross sections were surveyed with a total station while pebble counts characterized the river substrate pre- and post-dam removal. The results from the conventional measurement approaches were compared to the measurements made from the imagery products to help determine the efficacy of the aerial approach for measuring geomorphic change. In addition, ways to potentially correct inaccuracies in the sUAS-derived topography are discussed. The sUAS methods are a promising, low-cost approach to evaluating ecological impacts from dam removal and other river management.

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