Gravel Deposition and Island Formation in Dammed and Undammed River Systems – Anassessment of spiny softshell turtle nesting habitat using UAS visual data and NAIP imagery

Riverine species have life history traits connected to the natural spring-flood pulse of rivers.
Dams in the western United States (US) have modified sediment transport and deposition rates
resulting in a decline of islands and channelization. A challenge that exists in assessing the
effects of dams is finding ecologically intact rivers as models of “natural dynamics”. The
Yellowstone River is the longest undammed river in the conterminous US and has a healthy
population of spiny softshell turtles—a riverine species of concern. We conducted spiny
softshell turtle population assessments from 2015–2020 on the Yellowstone and its largest
tributary the Bighorn River. We identified significant differences in population abundance and
impaired reproduction and juvenile recruitment on the dammed Bighorn River. To understand
differences in habitat on both rivers, we used ARC-GIS to extract potential nesting habitat (sand
and gravel) from NAIP imagery. This approach revealed differences in key nesting habitat
metrics, such as island numbers, yet the NAIP resolution and temporal variations of available
data complicated robust analyses. We propose using unmanned aerial systems (UAS) to gather
higher resolution visual spectrum data on 40km of each river near their confluence. UAS
imagery will facilitate survey date flexibility (just after peak flows) and collection of highresolution imagery will allow more accurate classification of suitable nesting habitat. Testing the
efficacy of UAS drone technology to assess ecosystem change and relate those changes to
species populations is the type of real world applications that NASA is interested in further
developing. 

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