Drones and Digital Photogrammetry: From Classifications to Continuums for Monitoring River Habitat and Hydromorphology

摘要

Recently, we have gained the opportunity to obtain very high-resolution imageryudand topographic data of rivers using drones and novel digital photogrammetricudprocessing techniques. The high-resolution outputs from this method areudunprecedented, and provide the opportunity to move beyond river habitat classificationudsystems, and work directly with spatially explicit continuums of data.udTraditionally, classification systems have formed the backbone of physical riverudhabitat monitoring for their ease of use, rapidity, cost efficiency, and direct comparability.udYet such classifications fail to characterize the detailed heterogeneityudof habitat, especially those features which are small or marginal. Drones anduddigital photogrammetry now provide an alternative approach for monitoringudriver habitat and hydromorphology, which we review here using two case studies.udFirst, we demonstrate the classification of river habitat using drone imageryudacquired in 2012 of a 120 m section of the San Pedro River in Chile, which was atudthe technological limits of what could be achieved at that time. Second, weudreview how continuums of data can be acquired, using drone imagery acquiredudin 2016 from the River Teme in Herefordshire, England. We investigate the precisionudand accuracy of these data continuums, highlight key current challenges,udand review current best practices of data collection, processing, and management.udWe encourage further quantitative testing and field applications. If currentuddifficulties can be overcome, these continuums of geomorphic and hydraulicudinformation hold great potential for providing new opportunities for understandingudriver systems to the benefit of both river science and management.