Using Remote Sensing Techniques to Examine Changes in Vegetation Following Dam Removal and Installation of a Nature-like Fishway

Dams throughout New England are aging and degrading, sparking discussions about their fates. Many dam owners are turning to dam removal as a solution for environmental and safety concerns, but the full, long-term ecological impacts of these removals are often site specific and are not fully understood. The installation of nature-like fishways is an alternative to full dam removal that could restore fish passage at the former dam site while helping to maintain upstream established vegetation and habitat. Researchers from University of New Hampshire (UNH) and University of Rhode Island (URI) are collaborating to assess the impacts of a dam removal and nature-like fishway installation on the Pawcatuck River in Bradford, RI. URI has been conducting conventional monitoring of upstream vegetation plots pre- and post-fishway installation at the Bradford Dam following the Stream Barrier Removal Monitoring Guide (Collins et al. 2007), which collects data on the presence of invasive species and estimates vegetation structure by tree canopy, shrubs, and herbaceous cover. Subsequently, UNH researchers flew a DJI Phantom 3 Professional small unmanned aerial system (sUAS) to collect imagery of the vegetation plots post-fishway installation. This imagery was processed in Agisoft PhotoScan Professional structure-from-motion software to create digital surface models and orthomosaics of the study site for use in GIS vegetation analysis. Vegetation percent cover estimates obtained from the sUAS imagery products are compared to those from the conventional assessment on the ground to evaluate the efficacy of the sUAS approach. This imagery provides a baseline for ongoing monitoring efforts.