Snow-Melt Triggered Debris Flows Affecting Utah's Megalopolis

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by Bruce N. Kaliser, Hauskins & Beckwith, United States,
James E. Slosson, Hauskins & Beckwith, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract: During the abnormally wet years of 1983 and 1984, debris flows were triggered late in spring on the west flank of the Wasatch Mountains and elsewhere in Central Utah. These debris flows impacted the cities of North Ogden, Farmington, Bountiful, Salt Lake City, and intermediary towns. In late May of 1983 the snowpack peaked, a full 1 1/2 months later than normal. At elevations of 8,000' the equivalent of 40 to 60 inches of water occurred on snowpack, and across Utah snow cover percentages ranged from 250 to 8000 percent of normal. Temperatures climbed suddenly, accelerating snowmelt and rapid runoff. Thunderstorms further exacerbated an already abnormal runoff. All of the debris flows were initiated as slope failures, mostly in the volume range of 1,000 to 20,000 yds3. The volumes of material that were ultimately deposited on alluvial fans were greatly in excess of the original source failures. The additional material was derived from regolith on slopes and particularly from scoured channel alluvium.

Subject Headings: Snowmelt | Solids flow | Debris | Material failures | Failure analysis | Runoff | Slopes | Utah | North America | United States | Salt Lake City

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