Alluvial Fan — The Day a Dam Failure Rewrote the Valley
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Transcript
The boulder field at Alluvial Fan looks geological, and it is—but the event that produced its modern form was partly human.
On July 15, 1982, Lawn Lake Dam failed high above the Fall River valley. A huge surge of water rushed downstream, carrying trees and boulders. When the flow reached the flatter valley near here, it spread out and deposited a fan of debris.
The flood killed people downstream and caused major damage. It also exposed the risks of old private dams that had been inherited inside a national park.
An alluvial fan is normally associated with repeated floods over long periods. Here, one catastrophic event created a remarkably visible example within hours. That makes the site an unusual fusion of geomorphology and infrastructure history.
The lesson is uncomfortable but useful: protected landscapes still contain human structures, and those structures can become geological agents when they fail.