Lake forming near landslide could break and rush towards Collbran. Residents of the area are warned to be ready to evacuate.
(Photo: Jim Terry)
GOLDEN – The massive landslide that poured down from Colorado's Grand Mesa on Sunday reshaped part of the geography in that area and also created a brand new lake.
According to members of the United States Geological Survey based out of Golden, a makeshift dam holding that lake in place has the potential to break and flood nearby creeks as well as the town of Collbran.
"Our fear is that the water breaching might mix with a lot of [debris] and form a large volume, high speed, debris flow – going down West Salt Creek and then eventually into ... Plateau Creek that goes in to Collbran," said Edwin Harp, a research geologist with the USGS in Golden.
Harp has worked for the USGS for more than 40 years. He doesn't recall ever seeing a lake form behind a landslide in Colorado.
"Nothing where a big lake formed. There may have been small streams, but nothing as big as this has happened," Harp explained.
No one's quite sure how large the lake is or how fast it's growing. Geologists say two waterfalls are pumping more water into the lake every second.
"We really haven't evaluated how big the body of water is behind it and how big it's going to be before it overtops, but we're trying to work out the uncertainties on that so we can decide how far downstream there might be a problem," said Harp.
The big concern is whether the lake water is mixing with shale from the landslide.
"We don't think the shale [from] the landslide damage is really stable. We suspect it will erode and cut through. But the question is 'how fast will it breach? Will it breach really catastrophically or will it be somewhat slower?'" Harp added.
The USGS has two geologists at the site. They were collecting information Thursday afternoon, and they plan to present it to the county and state.
"That takes some time, and we might not have that time to do all that before some breaching occurs. In which case, we'll have to make a very conservative judgment as to how many people need to get out of the way of it and what area will be affected," Harp said.
It's unclear when the dam will break or if the water will breach. Even if it does, Harp says it might not be too devastating. However, in situations like this, Harp says it's always a good idea to plan for the worst-case scenario.
"If we know sometime approximately when the dam breach is going to occur, we need to get out of the way, let it happen and then go back and reassess whether we can get back to our houses or not," he said.
Hundreds warned to be ready to evacuate
During a public meeting Thursday evening, geologists warned residents of the area that they should be ready to evacuate. They said they do not know for sure if a second slide will happen but if does, Plateau Creek is most at risk.
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