Comment: 16:48 - 18:12 (01:24)
Source: Annenberg/CPB Resources - Earth Revealed - 16. Mass Wasting
Keywords: "Wade Wells II", "U.S. Forest Service", hydrologist, "flood control channel", mountain, mudflow, rainfall, mud, "geologic hazard", Wrightwood, "San Andreas Fault", fault, bedrock, "mass wasting"
Our transcription: This flood control channel was built to protect the community of Wrightwood from the mudflows that come off the nearby mountains after particularly wet winters.
Wade Wells is a U. S. Forest Service Hydrologist concerned with the control of mudflows.
These channels have proven themselves to be very effective in protecting most communities.
It's only in the worst years that we have a problem with the channels being overtopped and houses being covered with mud or destroyed and knocked off their foundations, things like that.
Channels like this one, however, do require a great deal of costly maintenance.
During every year and after every rainy season we come in with bulldozers, skip loaders, and trucks, and we carry out, we take the material and carry it away to a suitable disposal site.
One reason the Wrightwood area is vulnerable to mudflows is the proximity of the San Andreas Fault, which has deeply shattered the bedrock composing the mountainside above the community.
The flows that damaged Wrightwood in 1941 came from about the eastern third of that scar.
It's widened to the west since that time until it's reached its present size.
This indicates that the whole area is active, and the fact that there's nothing growing up there in the scar area means that it moves so much, so often, and so rapidly, that it'll probably be that way for several years, several hundreds of years hence.
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