Well, I think we might need a dedicated thread for this. @afterspivak , this is partly due to our exchange related to the typhoon thread.
Things are looking precarious for the folks in Guangfu. Let’s hope this turns out to be nothing.
Authorities in Hualien County are preparing for possible large-scale evacuations as Typhoon Fung-Wong approaches Taiwan, with officials warning that extreme rainfall could trigger the formation of a new landslide lake on Mataian River (馬太鞍溪).
The Forestry and Nature Conservation Agency said yesterday that a new barrier lake could form if three extreme conditions occur simultaneously – 24-hour accumulated rainfall of 800 millimeters, the collapse of the existing Mataian barrier lake holding about 1.5 million cubic meters of water, and a massive slope landslide blocking the river channel.
If these conditions are met, the resulting lake could store up to 15 million cubic meters of water and, if it later collapses, could unleash floodwaters at a peak rate of around 4,500 cubic meters per second, the agency estimated.
A new barrier lake that formed on Matai’an Creek in Hualien County overflowed and flooded Mingli Village in Wanrong Township again Thursday afternoon, according to the Hualien branch of the Forestry and Nature Conservation Agency (FANCA).
The landslide lake is still 1002m deep, estimated to hold 98.1k cubic meters of water, and the landslid dam is made of very unstable debris. There is no safe way to demolishing it without immediately endangering people living downstream.
The water-level on that chart may reflect it’s elevation. It’s a glacial valley with peaks over 3000m on both sides (Mount Nokou and Mount Maqudas). The landslide dam itself is 1139m abive sea-level. It also happens to be one of the steepest part of the central mountain range. The village of Fata’an is only 10km horizontally from the landslide lake, but for every kilometer, there is more than 100m change in altitude.
So right now the water level is no where near the rim of the dam, assuming no significant erosion has happened to the landslide dam itself.
A team of 14 workers mannuallyand gradually lowered a portion of the dam for the past month and almost drained all of the water in the dam. Afterwards they were evacuated by a helicopter.
