A Study of the Impacts of Freeze–Thaw on Cliff Recession at the Calvert Cliffs in Calvert County, Maryland

Abstract

The Calvert Cliffs, which form much of the western coastline of the Chesapeake Bay in Calvert County, Maryland, are actively eroding and destabilizing, yielding critical situations for many homes in close proximity to the slope’s crest. Past studies have identified that waves directly interacting with the slope toe control cliff recession; however, where waves do not regularly interact with the slope toe, freeze–thaw controls recession. This study investigated the validity of this second claim by analyzing the recession rate and freeze–thaw behavior of six study sites along the Calvert Cliffs that are not directly affected by waves. While waves do remove failed material from the toe in these regions, freeze–thaw is believed to be the dominant factor driving recession at these sites. Past recession rates were calculated using historical aerial photographs and were analyzed together with a number of other variables selected to represent the freeze–thaw behavior of the Calvert Cliffs. The investigation studied sixteen independent variables and found that over 65 % of recession at these study sites can be represented by freeze–thaw through the following variables: (1) slope aspect, (2) soil freeze–thaw susceptibility, (3) the number of freeze–thaw cycles, and (4) the weighted shear strength. Future mitigation techniques at these sites should focus on addressing these variables. Unmitigated, the Calvert Cliffs will continue to recede until a stable slope angle is reached and maintained.