Many waterfalls have deep plunge pools that are often partially or fully filled with sediment. Sediment fill may control plunge-pool bedrock erosion rates, partially determine habitat availability for aquatic organisms, and affect sediment routing and debris flow initiation. Currently, there exists no mechanistic model to describe sediment transport through waterfall plunge pools. Here we develop an analytical model to predict steady-state plunge-pool depth and sediment-transport capacity by combining existing jet theory with sediment transport mechanics. Our model predicts plunge-pool sedimen

thousands of years, the plunge pool at the waterfall base continued to expand, creating a large overhanging precipice and cavern where the hard basalt San Rafael Falls (Spanish: Salto de San Rafael) was a waterfall on the Coca River in Sucumbíos and Napo, Ecuador. Standing 131 metres (430 ft) high, it was the tallest and most powerful waterfall in Ecuador and a popular tourist attraction. The falls were located at the eastern boundary of Cayambe Coca National Park, in the eastern Andean foothills about 170 kilometres (110 mi) to the east of Quit The debris flow material downstream of the lava dam washed away, increasing the drop to over 130 metres (430 ft). Over thousands of years, the plunge pool at the waterfall base continued to expand, creating a large overhanging precipice and cavern where the hard basalt layer rested atop the loose material below. At this point, the knickpoint became relatively stable, with the overhanging basalt protecting the loose material below from further upstream erosion. The area around El Reventador remains tectonically active. A March 1987 earthquake caused large debris flows into the Coca River that reached San Rafael Falls. The debris flows reached an estimated depth of 20 metres (66 ft) at the falls. Prior to the collapse, the falls were a major tourist attraction for the area. In 2019 about 30,000 people visited the falls. The falls were accessible by an approximately thirty-minute hike from nearby Hostería El Reventador (about 50 kilometres (31 mi) by road northeast of El Chaco) which brought visitors to a scenic view point, "La Mirador", above the falls. Although located near the Cayambe-Coca National Park, the falls themselves were actually on a small private preserve. In 2010, construction had begun on the Coca Codo Sinclair Dam about 19 kilometres (12 mi) upstream from the waterfall. The 1,500 megawatt hydroelectric plant, Ecuador's largest power station, was designed to divert water around a large bend ("codo") of the Coca River, utilizing the natural drop of the waterfall and river to generate power. Despite creating significant controversy over its ecological impact and its potential to reduce the flow of the waterfall, the project was completed in 2016. The developers of Coca Codo Sinclair promised to maintain a minimum flow of 22 cubic metres per second (780 cu ft/s) over the falls, or about one-quarter of its typical dry season flow. The waterfall had been undergoing noticeable geomorphic changes since the 1990s, when it fell in two distinct stages: a smaller upper cascade followed by a large lower plunge. By about 2010, much of the lower lip of the falls had eroded away, bringing the two tiers close together; in 2015 that section collapsed completely,…