Development on or near bluffs and steep slopes often results in erosion, slope failure, landslides, and visual impacts to these sensitive natural features. Geological factors include bedrock type and location, soil type, slope angle. Hydrological factors include the quality of vegetation cover, intensity and duration of precipitation, and the presence of springs. The interaction of these factors affects bluff and slope stability. Land development and land alteration change the way water moves across and through the land and along with increased frequency and intensity of rainfall can increase risks.
Professional inventories and studies can help communities better assess failure risk, so they can put appropriate measures in place to ensure future development is safe and does not increase risk. To learn what other communities are doing and available resources, see:
- Historical Landslide Inventory for the Twin Cities Metropolitan Area - this report will serve as the basis for an upcoming statewide inventory of landslide hazards
Strategies for Reducing Risk of Slope Failure
Strategies for reducing the risk of slope failure will vary depending on local risk factors. General approaches include:
- Surface grading on or near slopes to minimize slope erosion and saturation of slopes
- Establishing and maintaining vegetation that helps stabilize slopes
- Using erosion-control and stormwater management measures to reduce erosion and overland flow
- Planning and zoning land for uses compatible with bluffs and steep slopes
- Regulating placement and design of structures and land alteration in bluff and steep slope areas
- Public education and outreach
The following materials provide basic information on the risks and mitigation approaches for local governments and property owners:
- Landslide Mitigation Strategies
- Bluff Protection Standards in Minnesota
- Management of Bluffs and Slopes Info Sheet
Bluff and Steep Slope Identification
It can be difficult to determine whether a slope meets the bluff definition without field verification. An onsite survey is recommended for regulatory and building purposes. For other purposes, approximate locations of a bluff can be determined using digital methods.
Digital Methods for Bluff Identification
The following methods use LiDAR-based elevation data to identify where bluffs may exist. These resources are for planning purposes.
- The DNR Bluff Mapping Tool is a GIS-based add-on available on the Minnesota Geospatial Commons.
- For quick analysis of a specific site, follow the tutorial for Identifying Bluffs and Steep Slopes Using MnTOPO.
Field Survey Methods for Bluff Identification
A field survey is necessary to locate definitive bluff boundaries for building purposes.