Shoreline reaches examined by Dave Mickelson and assistants, University of Wisconsin-Madison

Stable Slope Angle

Stable slope angle of materials in bluff, generalized over the reach. The stable slope angle is our best estimate, but unusual groundwater conditions, removal of vegetation, gully growth, etc. may create problems even at the stable slope angle. In some cases the shore is so variable, no single number is given, and these require on-site evaluation.

Estimates of stable slope angles (degrees) for various materials:
Douglas till – 14
Jardine Creek and Loamy Douglas till – 26
Sand and gravel and disturbed bedrock – 30
Bedrock – 60

Where one material overlies another in the bluff, the percentage of the bluff height of each material is given (eg. 20%14/80%60) means the top 20 percent of the bluff is made up of Douglas till with a stable slope angle of 14 degrees the lower 80 percent is bedrock with a stable angle of 60 degrees.

All of the above numbers are estimates, and if a qualified engineer or geologist can document different material or material properties at a site than those show in the table, then these would be accepted.

Estimated Bluff Height

This is a generalized number and a field measurement would be used to determine actual setbacks. It does not account for many gullies or other irregularities in the bluff.

Recession Rate

This recession rate in feet/year is estimated from aerial photos (1966 and either 1996 or 2005) and by visual inspection of oblique photos from 1978 and 2005. Future recession could be different under different lake-level scenarios. Wave protection structures have not been considered and recession rate was not estimated for non-bluff shorelines.