Measuring the Morphology and Dynamics of the Snake River by Remote Sensing
The Snake River is a prominent, central feature of Grand Teton National Park, and this dynamic fluvial system maintains diverse habitats while actively shaping the landscape. Although the riparian corridor is relatively pristine, the Snake River is by no means free from anthropogenic influences: streamflows have been regulated since 1907 by Jackson Lake Dam. Among dam-controlled rivers in the western U.S., the Snake River is unique in that tributaries entering below the dam supply sufficient coarse bed material to produce a braided morphology. As a result of tributary inputs, sediment flux along the Snake River has been relatively unaffected by Jackson Lake Dam, but flow regulation has reduced the magnitude and altered the timing of streamflows. In this study we are coupling an annual image time series with extensive field surveys to document channel changes occurring on the Snake River. Our objective is to quantify how snowmelt runoff events and flow management strategies influence patterns of sediment transfer and storage throughout the river system, with a particular focus on tributary junctions. More specifically, we are using the image sequence to identify areas of erosion and deposition and hence infer the sediment flux associated with the observed changes in channel morphology. This analysis will improve our understanding of the riverâs response to flow management and enable us to generate hypotheses as to how the system might adapt to future anthropogenic and/or climate-driven alterations in streamflow and sediment supply. In addition, our research on the Snake River involves an ongoing assessment of the potential to measure the morphology and dynamics of large, complex rivers via remote sensing. A new aspect of this investigation involves estimating flow velocities from hyperspectral images that capture the texture of the water surface. Extensive field measurements of velocity and water surface roughness are being used to develop this innovative approach and thus increase the amount of river information that can be inferred via remote sensing.