LANDSLIDES IN NORTH DAKOTA: AN OVERVIEW OF THE LANDSLIDE INVENTORY MAPPING PROGRAM AT THE NORTH DAKOTA GEOLOGICAL SURVEY

Landslides occur in natural and anthropogenic settings in North Dakota and are most commonly found within major river valleys and on engineered slopes along major transportation corridors. A focused, observational landslide inventory mapping program, ongoing since 2000, has mapped over 8,856 individual landslides over a mapping area of 36,000 km² (8.9 x 10⁶ acres). Landslides are dominantly found in two settings, controlled by the surface geology of the Great Plains in western and southwestern North Dakota and along major river valleys of the Missouri, Sheyenne, James, Souris, and Red Rivers. Mapped landslides are typically large slump failures occurring in Early Cenozoic strata of the Fort Union Group in western and southwestern North Dakota, and within Late Cretaceous shales of the Pierre Formation in eastern North Dakota. Localized riverbank slumping within cutbank meanders in Pleistocene glaciolacustrine sediments of the Sherack and Brenna Formations, occur in the Red River Valley. Slope failures found along ND HWY 22 in western North Dakota, on Riverview Drive in Valley City, and along the Red River near Drayton, are recent examples of this recurring geologic hazard.