BEACH RESPONSE TO LONG PERIOD LAKE-LEVEL VARIATION

William L. Wood, Lee L. Weishar

Abstract


A 4-year set of beach and offshore profiles, measured at monthly intervals, is evaluated to determine the effect of wind-wave forcing and long period (1 year or greater) lake-level variation on beach profile change in the "tideless" Great Lakes. This evaluation indicates two distinct regions of change in the beach and nearshore area of these profiles. The beach-berm region responds directly to lake-level modulation of wind-wave forcing. This response occurs on two time scales (seasonal and long period), but always in direct relation to mean lake-level variation. The inner-bar actively changes under the influence of wind-waves, but appears to lack a well-defined seasonal pattern. Empirical eigenfunction analysis is applied to these data in order to statistically quantify the significance of these observed changes. This analysis provides confirmation of a hypothesized long-period (years) variation of the beach and berm in direct response to lake-level variation.

Keywords


beach response; long period level variation; lake level

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