Stream restoration monitoring using Structure-from-Motion photogrammetry, Teton Creek, Idaho

Stream restoration is a rapidly growing field in applied fluvial geomorphology. Monitoring provides an essential tool for tracking restoration project success, and can improve a project's effectiveness, but often is neglected due to budgetary limitations. This research investigates the potential of Structure-from-Motion photogrammetry to provide an inexpensive and accurate method for monitoring river restoration projects. Structure-from-Motion field survey data was collected in the summer of 2014 to evaluate the performance of a recent stream restoration project intended to reduce erosion along a 1.9 km reach of Teton Creek in eastern Idaho. Channel changes were quantified by creating a digital elevation model of difference that compared an initial, as-built Global Positioning System survey to Structure-from-Motion photogrammetry data collected one year after project completion. A morphological sediment budget and a two-dimensional flow model were used to investigate sediment transport within the study reach. We also used high resolution data derived from Structure-from-Motion point clouds to create continuous grain size maps for Teton Creek that in turn were used to estimate critical shear stresses for sediment entrainment. Our findings suggest Structure-from-Motion techniques provide valuable tools for river managers seeking to monitor restoration efforts. For example, we employed terrain products derived via Structure-from-Motion to verify that hardened riffle treatments effectively prevented erosion. Similarly, we demonstrated the utility of Structure-from-Motion for evaluating the sediment mass balance within the project area. This research establishes a framework for conducting Structure-from-Motion surveys of streams for use in restoration design and monitoring.