Coca River Regressive Erosion Phenomenon, Causes and Impacts. Overview of The Problem

The natural collapse of the 150 m high San Rafael waterfall triggered a process of regressive erosion of the Coca river, which rapidly degraded the river bed. As a result, the side slopes of the channel were undermined and the river valley widened dramatically. In the aftermath, numerous infrastructures that were found in the course of the river and its vicinity (oil pipelines, roads, transmission lines, private properties, etc.) were destroyed and had to be repositioned or modified immediately. The most prominent infrastructure threaten by the advance of the erosion is the Coca Codo Sinclair (CCS) hydropower plant, which is located about 20 km upstream the location of the former waterfall, and contributes up to 30% of the total energy demand of Ecuador. Approximately 250 hm3 of sediment have been eroded and the headcut propagation rate has the potential of reaching the power plant intake within the next decade. CELEC EP which is the Ecuadorian Electric Corporation, through the Río Coca Executive Commission, is in charge of carrying out the necessary studies and works to protect the hydroelectric plant facilities against the implications of the ongoing erosion and sedimentation. This paper summarizes the importance and benefits of the Coca Codo Sinclair power plant for Ecuador, the genesis of the problem and all actions that CELEC have performed since the waterfall collapse. Among these actions, the discussion focuses around the ongoing studies and analysis of the erosion evolution, construction plans for mitigation measures (emergent and permanent ones), and the international collaboration and assessment established with the USACE in order to prevent the potential operation interruption of the CCS hydropower plant.