San Rafael Falls, or Cascada de San Rafael, has been the tallest waterfall in Ecuador for at least a millennia and one of the major attractions in the Cayambe-Coca Ecological Reserve. That changed in early 2020, when an enormous sinkhole opened in the middle of the Rio Coca, swallowing the river and diverting it underneath the previous lip of the falls. It now emerges from a large cavern next to where the falls previously were.
Cascada de San Rafael, March 2019 (This Wild Wonderland)
Some scientists link the collapse to a recent hydroelectric dam project that opened 20 km upstream of the falls several years ago. They believe that there is likely a link due to the effect that water with less sediment has on erosion. The dam has powerful filters that remove nearly all sediment from the river. Water with less sediment has a much higher potential to erode and therefore might have greatly accelerated this natural process. Emilio Cobo, coordinator of the IUCN (International Union for Conservation of Nature) Water Program for South America states, “A waterfall that has been there for thousands of years does not collapse, coincidentally, a few years after opening a hydroelectric project. These are processes that are in scientific paper and there is sufficient evidence that a dam can cause effects of this type on a river.”
“A waterfall that has been there for thousands of years does not collapse, coincidentally, a few years after opening a hydroelectric project..."
However, other scientists believe the waterfall’s disappearance is a natural phenomena caused by naturally occurring erosion and the lingering effects of the many earthquakes this region experiences. Alfredo Carrasco, a geologist and former secretary of Natural Capital at the ministry, says, “There are many quite intense earthquakes here. In March 1987, a very strong one appeared that caused tremendous damage to the trans-Ecuadorian oil pipeline that passes right through it. That year I had the opportunity to evaluate the impact of earthquakes in that area. There were floods of up to 20 meters above the level of the valley where the river passes. It is very typical that the energy of the water falling erodes the base. For me, the phenomenon is eminent of natural origin.”
Whether or not the waterfall’s disappearance was caused by human activities, its loss will continue to have major impacts in several areas beyond the loss of its great natural beauty. Since the hard rock that was the lip of the waterfall is now being bypassed and the river is flowing through much softer soil, there has been a massive increase in erosion. As it erodes near the previous site of the falls, it triggers more erosion upstream in a process called regressive erosion. This has already destroyed a major bridge, ruptured two oil pipelines, disturbed important riparian habitat, and is threatening small communities along the Rio Coca and its tributaries. Ecuador has more rivers by area than any country in the world, which can make it especially susceptible to regressive erosion travelling far up a river and spreading wider among its tributaries.
Whether or not the waterfall’s disappearance was caused by human activities, its loss will continue to have major impacts...
Drone footage before and after the collapse.
Drone footage of upstream showing regressive erosion, potentially responsible for the rupture of two oil pipelines.
The governmental organization CELEC (Corporación Eléctrica del Ecuador) began conducting geological research in November 2020 and will continue to do so through next year. To mitigate, control and remediate the effects of river erosion, it will make an investment of more than 124 million dollars for studies and design, construction of works such as dams under the riverbed, purchase of equipment, and administrative expenses. We can hope that they can determine the root cause of this incident and prevent further harm.