SWENSON, M.J., WU, C.H., MICKELSON, D.M., and EDIL, T.B., 1269D Engineering Hall, University of Wisconsin-Madison, Madison, WI, 53706. Spatial variation of bluff recession along the Wisconsin shoreline of Lake Superior.

Detailed spatial measurements of bluff recession rates, beach and bluff profiles, and wave runup along the Wisconsin shoreline of Lake Superior were collected during the last three years. The bluffs are composed of relatively smectitie-rich (relative to Lake Michigan) clay, sandy clay, and sand. Beaches are composed of sand, and cobbles and boulders and have spatially varying morphology. An index of wave energy reaching the bluff, i.e., cumulative wave impact height, has been carefully validated in the field study at 26 sites along the Wisconsin shoreline of Lake Superior. The index accounts for changes in long-term and short-term water levels, short-term wave climate, and variability in coastal and beach morphology. Cumulative wave impact height is hindcast and compared to recession rates obtained from aerial photographs for the same period. Thus, cumulative wave impact height can be correlated to spatially varying bluff recession rates. In general, relationships exist between cumulative wave impact height and recession rates, but local differences in beach or bluff conditions that may be temporally transient (landslides, accumulations of wood on beach, etc.) produce significant variation in results.