Quantifying the geomorphic effect of floods using satellite observations of river mobility

Geomorphologists have long debated the relative importance of disturbance magnitude, duration, and frequency in shaping landscapes. For river-channel adjustment by floods, some argue that the cumulative hydrograph, rather than magnitude or duration, matters most. However, studies of flood-induced river-channel change often draw upon small data sets. Here, we combine Sentinel-2 imagery with flow data from laterally active rivers to address this question using a larger data set. We apply automated algorithms in Google Earth Engine to map rivers and detect their lateral shifting; we generate a large data set to quantify planform erosion during 175 floods at 34 selected sites. Erosion during these floods is best explained by their duration and then their cumulative hydrograph. We use a random forest regression model to predict flood-induced erosion, with potential applications for hazard management. Ultimately, better global data on sediment supply and caliber would help us to understand flood-driven change to river planforms.