7 May 2020
Planet Labs high resolution image of the Chesegon, West Pokot landslides
Posted by Dave Petley
Planet Labs high resolution image of the West Pokot landslides
Last week I posted about the devastating channelised debris flows that caused large numbers of fatalities in the vicinity of Chesegon, West Pokot in Kenya on 17 April 2020. This is only the latest set of such events in this region, which appears to be struggling under the combined impacts of unusually intense rainfall events, land degradation and a highly vulnerable population. My friends at Planet Labs have once again gone the extra distance to collect a high-resolution SkySat image of the impacts on this area. My thanks to them, and in particular to Rob Simmon, for collecting and processing the image.
The image below was captured on 30 April 2020, a little under two weeks after the landslides:-
The area affected by these landslides is very large, so the image inevitably captures only a part of it. The landslides were clearly devastating. The heavy population density of this area can be seen clearly; living close to the channels as these debris flows swept down would have been terrifying.
The greatest danger with these types of landslides lies when they sweep out of their channels to inundate inhabited areas. There are lots of examples of this style of behaviour in the Chesegon landslides. The image below shows a location where this has occurred twice, for example:-
The debris flows have inundated a large area. At the downstream (eastern) end they have inundated some properties, which remain standing with their roofs on. We should not be lulled into thinking that the inhabitants will have escaped though. In channelised debris flows fatalities often occur when flows enter properties, and in doing so block exit routes such as doors and windows. Those who are lucky enough to escape are often swept off their feet by the flows.
To date these rains across Kenya have killed 194 people in landslides and floods, including the impacts in the Chesegon area, and they are forecast to continue for several more weeks. Unfortunately, more such landslides could ocur in this rainy season, and in future years. An article in The Standard in Kenya highlights extensive pre-failure deformation on slopes across a large area. In one case the tension crack is reported to be 10 km long. There is an urgent need to understand what is occurring on these slopes, and why, and to assess the risk, but I fear that landslides in Kenya will appear on this blog again in the coming years.
On reflection 1: Day 4 of the EGU General Assembly online
It’s a bumper day of landslide sessions today:
On reflection 2: dams and erosion
Massive erosion on the Coca Rover in Ecuador is being linked to sediment management for a major hydropower project.
Planet Team (2020). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/