8 February 2022
Planet Labs imagery of the 31 January 2022 mudflow in the La Gasca suburb of Quito
Last week I posted about the 31 January 2022 mudflow at La Gasca in Quito, Ecuador. Two loyal readers, Stephen Slaughter and Doug Clark, have kindly highlighted that a few days ago the sky was sufficiently clear for Planet Labs to capture a good PlanetScope image of the site, which is revealing:-
The track of the mudflow, in an existing channel, is clear, running approximately west – east across the middle of the image. It is clear that the volume was increasing along the track and just to the east of the centre of the image it appears to bifurcate. On the eastern side of the image the damage to the city can be seen, although with little detail. Interpretation is helped considerably by a drone video on the El Comercio website, which shows that the mudflow followed the incised channel to the north of the vegetated area just south of Teresa Silva, and then directly down the road network.
The resolution of PlanetScope images makes interpretation of mechanisms of initiation quite difficult, but it is interesting to take a look at the upper parts of the channel:-
There is no obvious landslide on the terrain adjacent to the channel that might have been the initiating event for the mudflow. It seems likely therefore that it started either as a very localised failure that is too small to resolve or as an in-channel event in which the flow initiated bank erosion and/or entrainment of the channel bed. It is clear that the majority of the mudflow that struck La Gasca was formed from material eroded from within the channel.
With climate change causing an increase in rainfall intensity, there is a high likelihood of a repeat of this event. Mitigation of the channel is needed, along the line of the Japanese sabo engineering approach (ideally using more environmentally-conscious engineering approaches than is sometimes the case).
Finally, many thanks to Stephen and Doug for highlighting the imagery to me. Finding time to write this blog is a challenge at times, it is made so much easier when loyal readers provide help like this.
Planet Team (2022). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/