Long-term recession rates of Lake Michigan's shorezone bluffs were investigated at 118 sites by comparing modern measurements with nineteenth-century Government Land Office surveys. These rates were evaluated spatially and related to selected shorezone characteristics. One hundred and six of the bluff sites are experiencing retreat that averages 0.4 rn (1.3 ft) per year. Although amounts vary significantly, average values show that (1) rates are similar for opposite sides of the lake but (2) values differ between northern and southern Wisconsin. In addition, dune-encompassed bluffs tend to recede at lower long-term rates than nondune bluffs. Groundwater seepage, shoreline orientation and fetch, and shorezone protective structures are some of the factors found to influence bluff crest recession. Data from this study indicate that extensive Lake Michigan shorezone tracts will continue to experience bluff recession measurable in meters per decade unless lake levels are relatively low or unless protective devices of massive proportion are constructed along much of the shoreline.

No abstract

No abstract

No abstract