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Beaver dam analogs (BDAs) are being installed on streams where restoration goals include reconnecting the stream to its floodplain, increasing water storage in the stream corridor, and improving the extent and vigor of riparian vegetation. This study evaluated the effects on vegetation vigor of a BDA treatment on Blacktail Creek in southwest Montana, USA, using data from Sentinel-2 satellites and a small unmanned aerial system (sUAS; a.k.a. drone). The goal of this research was to determine if BDA installation increased the health of riparian vegetation. Sentinel-2 remote sensing data from 2016 to 2021 were used to compare the pre- and post-treatment periods, and to evaluate effects in the treated area relative to control areas. Enhanced Vegetation Index (EVI) values were calculated to quantify vegetation response from the addition of BDAs. These data suggest that installing BDAs at this site has not led to an apparent increase in late-summer vegetation vigor relative to the controls. One potential explanation for these results is that the vegetation was not water limited prior to treatment in this study reach. This is an important consideration for water resource managers prior to installation of BDAs if the main restoration goal is the improvement of riparian vegetation health. Two high spatial resolution sUAS multispectral datasets were collected to evaluate the bias introduced by using the relatively course resolution (10 m) satellite imagery to assess these changes. High-resolution sUAS data allow fine-scale differences in vegetation and inundated area to be distinguished; however, historical sUAS datasets are rarely available. Satellite-based remote sensing has much lower resolution; however, Sentinel-2 satellite data have been available for the entire earth since 2016. This study demonstrates that the combination of sUAS and satellite based remote sensing data provides a method to compare high-resolution datasets for spatial analysis while gaining insight into relatively low-resolution historical data for temporal analysis. Full article

Degradation of streams and associated riparian habitat across the Missouri River Headwaters Basin has motivated several stream restoration projects across the watershed. Many of these projects install a series of beaver dam analogues (BDAs) to aggrade incised streams, elevate local water tables, and create natural surface water storage by reconnecting streams with their floodplains. Satellite imagery can provide a spatially continuous mechanism to monitor the effects of these in-stream structures on stream surface area. However, remote sensing-based approaches to map narrow (e.g., <5 m wide) linear features such as streams have been under-developed relative to efforts to map other types of aquatic systems, such as wetlands or lakes. We mapped pre- and post-restoration (one to three years post-restoration) stream surface area and riparian greenness at four stream restoration sites using Worldview-2 and 3 images as well as a QuickBird-2 image. We found that panchromatic brightness and eCognition-based outputs (0.5 m resolution) provided high-accuracy maps of stream surface area (overall accuracy ranged from 91% to 99%) for streams as narrow as 1.5 m wide. Using image pairs, we were able to document increases in stream surface area immediately upstream of BDAs as well as increases in stream surface area along the restoration reach at Robb Creek, Alkali Creek and Long Creek (South). Although Long Creek (North) did not show a net increase in stream surface area along the restoration reach, we did observe an increase in riparian greenness, suggesting increased water retention adjacent to the stream. As high-resolution imagery becomes more widely collected and available, improvements in our ability to provide spatially continuous monitoring of stream systems can effectively complement more traditional field-based and gage-based datasets to inform watershed management. Full article