Braiding Index Measurements, Río Coca, Ecuador, 2012–2023

On February 2, 2020, the Río Coca in Ecuador undermined a basaltic-andesitic lava dam that formed the 144-meter-high San Rafael waterfall. Following the failure of the lava dam, the sudden loss of grade control prompted rapid knickpoint retreat and regressive erosion into poorly consolidated sediment, which initially migrated tens of meters upstream per day. On February 25, 2021, the abandoned basaltic arch structure, which had formed the waterfall, collapsed completely. In the 4.5 years after the river first undermined the waterfall, the river eroded more than 13 kilometers upstream, removing and transporting more than 360 million cubic meters of sediment. The authors have chronicled the geomorphic evolution of the system before, immediately following, and in the years since lava-dam collapse through mapping of the braiding indices and unvegetated channel width. Geospatial data used to map this evolution are available as shapefiles.