DAVIS-WEBER CANAL LANDSLIDES - 1898 THROUGH 2006, DAVIS COUNTY, UTAH

The Davis-Weber Canal has a long history of damaging landslides. We use a newspaper database, geologic reports, and 1:24,000-scale landslide inventory maps to show the history of landsliding and damage along the canal. Six miles of the canal lie on steep slopes formed as the Weber River cut down into its former delta during the regression of late Pleistocene Lake Bonneville. These slopes contain numerous prehistoric and historic landslides and are generally composed of fine-grained lacustrine and deltaic sediments. Of the 49 landslides mapped along the canal, 23 underlie the canal and have historical movement.

Canal construction started in 1884 and landslides are reported as early as 1898. The types of landslide damage and elements at risk have changed through time. In the late 1800s and early 1900s, landslides involved only the canal and adjacent agricultural land. In the late 1900s, a transition from agricultural to urban land use and residential subdivision development below the canal dramatically changed landslide damage and risk. In 1999, a canal breach into a subdivision caused evacuation of 300 people. Flooding and sediment deposition caused severe damage to 15 houses and minor damage to 55 houses. A 2005 landslide removed part of the canal embankment, destroyed a barn, and covered State Highway 60 with landslide debris, necessitating highway closure. Canal repair and landslide stabilization cost $ 3 million and caused a delay in water delivery to irrigators. In 2006, another landslide flowed over and damaged the canal, destroyed a house wall injuring a child inside, and caused evacuation of nearby houses. The Davis-Weber Canal Company has established a program to evaluate landslide risk along the canal, prioritize canal reconstruction, and manage future landslide risk.