OF-06-03 Rockfall Hazard Susceptibility in Colorado Springs, El Paso County, Colorado

Describes potentially hazardous rockfall areas within the Colorado Springs city limits in El Paso County. The CGS worked with the City of Colorado Springs Planning Department to develop GIS coverages for potential rockfall hazard areas in 2003. The resulting map data has been compiled into this publication for use by planners, geologists, engineers, and public users. Includes a 1:24,000 map and a description explaining the hazard, mapping methodology, and implications to development in the area. Digital ZIP/PDF download. OF-06-03D

Rockfall is considered a geologic hazard in the Colorado Revised Statutes (C.R.S. § 24- 65.104), and local communities are encouraged to identify rockfall hazards and adopt land-use policies to regulate development in rockfall prone areas. This publication identifies these areas and describes the methods used to determine rockfall susceptibility within the study area. The rockfall susceptibility data was developed at a mapping scale of 1 inch = 800 feet (1:9,600) to discern rockfall areas identified during this study.

Rockfall occurrences are difficult to predict, and can range from a single rock falling or rolling to large-scale catastrophic events that can quickly demolish structures and injure or kill people. Rocks falling on highways may strike vehicles, block traffic, or cause accidents and road damage. The size of the falling rock depends on the source area geology (bedding thickness, bedding dip and dip direction, hardness, jointing/fracturing orientation), weathering, and position. Rolling or sliding rocks occur on steep slopes where loose rocks may mobilize from gravity (slope creep) or hillside development activity. This may occur in areas where loose rocks are located on steep slopes, regardless of the presence of an outcrop. However, most areas susceptible to rockfall can be identified and steps may be taken to avoid, reduce, or mitigate rockfall risk.