Forest fires create increased danger of destructive debris flows

Steep slopes denuded by forest fires are prime candidates for debris flows during our summer monsoon. A debris flow is a mixture of soil, cobbles, boulders, and water, with the consistency of concrete moving down a steep slope at 20 miles per hour or more. Typically debris flows are more destructive than floods.

In 2006, a particularly wet July spawned debris flows in the Catalina Mountains, the Chiricahua Mountains, and the Huachuca Mountains. Debris flows also occurred in 1977 and 1988 in the Huachuca Mountains. (See Arizona Geological Survey reports here and here.)

The Horshoe 2 fire in the Chiricahua Mountains has destroyed most of the vegetation in that range. We may have destructive debris flows this summer in the burned areas.

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