STRUCTURE FROM MOTION STUDY OF EROSION FROM MOBILE RIVER ICE

This work highlights the use of Structure from Motion Photogrammetry to determine eroded volumes for experiments studying the effects of mobile river ice on bank erosion and meandering. Experiments were conducted in a 4’ by 6’ stream table with constant discharge and meandering channels preconstructed in 4” of very fine sand. Experiments were divided into four, five-minute increments with sequences of imagery gathered between those periods. The first three experimental periods served as stabilization periods, with ice (simulated as paraffin wax) added continuously over the final five-minute period. Imagery from each break was processed into Digital Terrain Models for differencing over experimental periods. DTM’s and orthophotos produced from the photogrammetry were used to map the locations of ice-bank impacts for comparison to erosional results. Structure from Motion work was conducted in Agisoft Metashape, and DTM-differencing was conducted in ArcMap 10.6 using the Geomorphic Change Detection (GCD) tool. Results show net erosion over the entire experimental period, with most of the erosion occurring during the period of ice addition. Ice-bank impact mapping revealed that ice most frequently impacts outer banks of meander bends. These results support the idea that river ice is capable of contributing to river meandering during the spring thaw and show SfM’s effective application at the experimental scale.