21 July 2020
Rio Coca: a valley-blocking landslide in Ecuador caught on video
On 18 July 2020 a substantial landslide occurred on the Rio Coca in Ecuador, blocking the river. The landslide occurred between the Montana and Marker river junctions, is located in El Chaco canton in Orellana. The image below, published in El Universo, shows the aftermath of the landslide:-
The landslide has occurred on the outside of the river bend – a classic location for undercutting of the river to create instability – in weak (possibly volcanic) deposits.
This landslide is remarkable because both the initial failure and the breach event have been caught on video. This is the video, posted on Youtube, showing the failure:-
I am not sure as to the circumstances in which this video was captured, but am impressed by the coolness of the people at the site. The video is interesting in that it captures the precursory deformation of the landslide block.
A video of the breach of the landslide dam on the Rio Coca has also been collected and has been posted to Twitter:
.#Deslizamiento – Así fue el desfogue del represamiento del río Coca la tarde de ayer.
Se represó por un deslizamiento en la confluencia con el río Marker.
— ESPECIGEST (@ESPECIGEST) July 19, 2020
Whilst a video has also been posted to Youtube that shows the breach event underway:-
Reports suggest that the landslide was triggered by heavy rainfall and that the breach occurred about four hours after the initial failure. Whilst there is considerable erosion downstream, the nearest community on the Rio Coca was located about 50 km downstream, so little damage occurred.
Quickslide 1: Another valley-blocking landslide
Xinhua reports that a landslide has blocked a valley on the Qingjiang River, a tributary of Yangtze River, in Enshi Tujia and Miao Autonomous Prefecture, Hubei, China. Evacuations are underway.
Quickslide 2: Continued landslide damage in Nepal
Heavy rainfall associated with the monsoon continues to cause loss of life and extensive damage across Nepal. Many roads are blocked by landslides and, according to the DRR portal, at least 117 lives have been lost to landslides since the beginning of June. There is increasing awareness in Nepal that poor quality road construction is a major factor behind these landslides, an issue that we highlighted in a paper (Petley et al. 2007) 13 years ago:-
It is concluded that a major component of the generally upward trend in landslide impact probably results from the rural road-building programme, and its attendant changes to physical and natural systems.
Petley, D.N., Hearn, G.J., Hart, A. et al. 2007. Trends in landslide occurrence in Nepal. Natural Hazards 43, 23–44 . https://doi.org/10.1007/s11069-006-9100-3