Assessing regressive erosion effects: Unveiling riverside land use land cover changes post hydroelectric project construction

ESPOL researchers evaluated the impact of regressive erosion in the Coca River due to the operations of the Coca Codo Sinclair hydroelectric plant using satellite images. Until the second quarter of 2023, Ecuador's energy matrix was made up of 92% of electricity generated by hydroelectric plants, 7% by thermoelectric plants and 1% by non-conventional sources such as photovoltaic, wind, biomass and geothermal energy. This made Ecuador dependent on hydropower. However, focusing its electricity matrix on a single predominant type of energy generates some challenges, such as vulnerability to climate change.

On 27 October 2023, blackouts returned in Ecuador, which the country had not had since 2009, due to a period of drought that caused low water levels in the tributary rivers of hydroelectric projects. On the other hand, climate change is not the only challenge that Ecuador has faced due to the implementation of hydroelectric plants in the central and southern Andes and in the Amazon. On 2 February 2020, the San Rafael waterfall on the banks of the Coca River in Napo province collapsed. This fact became relevant when, months later, land subsidence and sinkholes became more frequent in the vicinity of the Coca River, affecting the operations of the Trans-Ecuadorian Oil Pipeline System (SOTE), the Heavy Crude Oil Pipelines (OCP) and threatening the operation of the Coca Codo Sinclair Hydroelectric Power Plant (CCSHP), the most important in the country, since it covers 34% of Ecuador's energy demand.

In response to these doubts, the authors addressed the problem of the impact of the operation of the CCSHP on fluvial dynamics in the vicinity of the Coca River, using remote sensing techniques. This is the first study that evaluates changes in land use and land cover in the area and analyses the processes of erosion, migration and deposition of the water body through a spatio-temporal evaluation, processing satellite images.

The results of this study reflect an acceleration of regressive erosion since the construction and implementation of the CCSHP, information that can be used as an initial tool to analyze the impact of hydropower in the upper Amazon and strengthen environmental protection and risk management policies. In addition, this study evaluated the dynamics of LULC changes in the Coca River sector, one year after the start of the CCSHP project (2017), as well as one year before (2019) and after (2021) the collapse of the San Rafael waterfall. Prior to this event, the forest cover was replaced by agricultural activities. After the collapse, the forest cover and areas of agricultural activities near the riverbanks were replaced by sand deposits and water bodies, relevant changes in the upstream stretch of the former San Rafael waterfall, denoting the drastic increase of regressive erosion in the sector, with an increase in the width of the river channel.

Regressive erosion in the Coca River is linked to the start of CCSHP activities. For this reason, it is important to evaluate the adverse impacts that the generation activities of this type of renewable energy can cause on the fluvial dynamics and, consequently, on the physical environment of the areas surrounding the Coca River. It is recommended to implement territorial control and disaster prevention measures for regressive erosion through constant satellite monitoring of changes in the riverbed and their impact on the use and coverage of its banks. These measures should be addressed in integrated teams that include the state government, the electricity industry, the oil industry and local governments, to be disseminated to decision-makers and affected populations, to mitigate risks.