Optical-Flow Raster Processing and Active Channel Detection for the 180° Experimental Alluvial Fan

This archive contains the raster products and processing workflow used to derive motion-based activity maps from overhead imagery for the 180° experimental alluvial fan. The optical-flow analysis was used to identify active surface-motion corridors during the analysed portion of the experiment, including both the progradational phase and the downstream-limited phase. The resulting rasters form the basis for the occupancy maps and activity-footprint comparisons presented in the manuscript. For each 1-minute image sequence, dense optical flow was computed from consecutive overhead images to estimate pixel-wise surface motion intensity. The resulting average optical-flow magnitude rasters represent the spatial pattern of visible motion across the fan surface during each minute. These rasters were then thresholded to remove weak, diffuse signals associated with low-motion or quasi-static water patches, and connected-region filtering was applied to retain the main coherent zones of activity. The final thresholded rasters therefore represent the planform footprint of active surface motion used in the subsequent occupancy and process-outcome analyses. This folder contains: OpticalFlow_raw_raster/ – GeoTIFF rasters of average optical-flow magnitude for each 1-minute image sequence, converted from the Python CSV output. These rasters preserve the continuous motion-intensity field before thresholding. OpticalFlow_thresholded_raster/ – Thresholded optical-flow rasters in which low-intensity values are removed and only the main connected high-motion regions are retained. These rasters represent the binary activity masks used to identify active channels and motion corridors. OpticalFlow_Raster_ChannelNetwork.Rmd – R Markdown workflow that (i) reads the optical-flow CSV files, (ii) converts them to rasters, (iii) applies the selected motion-intensity threshold, (iv) performs connected-region filtering to remove small isolated patches, and (v) writes the thresholded optical-flow rasters used in the analysis.