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
- U.S. Geological Survey Landslide Hazards Program
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
- Conserving Your Blufflands - Management Guide for St Croix River Property Owners
- 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. There are two methods off-site users can use to identify where bluffs may exist. These methods utilize LiDAR-based elevation data.
- The Minnesota DNR Bluff Mapping Tool is a GIS-based add-on available on the Minnesota Geospatial Commons.
- For a quick analysis of a specific site, use the tutorial for Identifying Bluffs and Steep Slopes Using MnTOPO.
These resources are for planning purposes. A field survey would be necessary to locate more definitive bluff boundaries for building purposes.