Understanding coastal change at mesotimescales is a prerequisite for developing predictive coastal response models and remains a "holy grail" for coastal scientists and engineers. The historical behavior of the Presque Isle strandplain on the North American Great Lakes provides insight into the complexities of net coastal response to a large set of geoenvironmental variables. Principal among these variables are high-frequency lacustrine transgressions and regressions of up to 1 meter in magnitude that occur at timescales of years to decades against a backdrop of longer term transgression (8 mm/y, 1901-97). Almost a century of coastal processes and anthropogenic modifications have resulted in nearshore net accretion of 15.5 × 10 6 cubic meters (161 × 103 m3/y) for this terminal end of a 36-kilometer-long coastal sediment dispersal system. Sediment eroded from the strandplain's updrift transgressive neck sector, coupled with additional inputs from mass wasting of an updrift bluff coast and beach nourishment, is dispersed primarily along-coast to build downdrift regressive shoreface and capping progradational strandplain depositional systems. Several general rules describe coastal change during quarter century-scale regressive and transgressive lake phases. The downdrift composite spit sector of Presque Isle is always accretional across the entire nearshore profile regardless of lake phase. The response of the updrift transgressive sector is highly variable, and shoreline recession occurs during both regressive and transgressive lake phases. During periods of minor forced regression (-2 mm/y), the Presque Isle nearshore undergoes moderate net erosion, whereas during major transgression (12-15 mm/y), it undergoes minor to major net accretion. In general, erosional and accretional areas migrate on-, off-, and alongshore because transgressive-regressive cycles influence the interaction of natural and anthropogenic sediment source environments with the wave field, which entrains and disperses sediment.
All Science Journal Classification (ASJC) codes
- Water Science and Technology
- Earth-Surface Processes