USGS Lahar Detection System

Until recently, most warnings of a lahar, or ash and debris-laden flood, rushing down a valley toward a town or city were based on visual sightings. By the time Redoubt Volcano in Lake Clark National Park, Alaska, first erupted on December 13, 1989, a USGS scientist had designed a prototype system for detecting a lahar as it moved. All three Acoustic Flow Monitors that had been installed detected a lahar, triggered by the dome collapse on April 6, 1990.

Pictured above: The largest lahar from Redoubt, 1990, flooded part of the Drift River oil storage terminal with muddy water. Dark pathways of the lahar on March 9 move past an oil terminal marked by the white rectangle in lower center of the photograph. Photo taken by J. Major on March 10, 1990.

Pictured above: Simplified schematic of acoustic-flow monitoring station first tested at Redoubt Volcano in Lake Clark National Park and now being piloted at Mt. Rainier National Park.

A pilot project is now under way to begin operation of an automated lahar-detection system in the densely populated Puyallup River Valley, which extends from Mount Rainier to Puget Sound. Upon detection of a lahar in the valley, the system is intended to issue an automatic notice to County emergency-management officials that would trigger immediate, preplanned emergency-response actions.

Pictured above: Four sequential illustrations of a landslide at Mount Rainier, Washington, about 5,700 years ago (illustrations from J. Vigil).