14 April 2022
Three very large landslides triggered by Tropical Storm Megi / Agaton
Over the last two days more information has started to emerge about the landslides triggered by Tropical Storm Megi / Agaton, which caused mayhem on the island of Leyte in the Philippines on 11 April 2022. The latest news on casualties is that at least 123 people were killed, the majority in landslides, but more remain missing.
This is a very large failure in deeply weathered materials. The source appears to be a shallow slide on a steep, forested hillslope, but note that there are at least two other sources, albeit substantially smaller. The landslide has spread considerably to affect a very large swathe of land. The small number of standing trees might suggest that it was a comparatively shallow flow, but to a human or a weak structure it would have been devastating. Note the houses on the margin of the landslide on the right side of the image.
A second major event occurred in the village of Pilar in Abuyog. Here at least 29 people are known to have died, but as many as 177 more are reported to be missing. This total is likely to reduce, but it is clear that the landslide here has been devastating.
I can find few images of this landslide online, but Youtube has a drone video of the site:-
I have taken this image from the video, providing a decent impression of the failure:-
This appears to be a deeper seated landslide that has transitioned into a flow. Note the stripping of the vegetation on the slope on the right side of the image, which suggests to me that this was a high runout speed event. I also wonder if this event generated a displacement wave.
There are some videos online of secondary failures at this site, such as this one:-
The power of even this smaller landslide is appalling.
This landslide is broadly similar to the one at Kantagnos, although on a smaller scale.
I have been trying to track down the locations of these three landslides. At the moment, I believe that the following at correct:
Kantagnos in Baybay: 10.677, 124.853
Pilar in Abuyog: 10.714, 125.048
Bunga in Baybay: 10.773, 124.785
The impact of these landslides, and there are reports of many other events as well, is very serious. Tropical cuclones often cause landslides in the Philippines, but not in April.