A STATISTICAL STUDY OF PROCESS-RESPONSE SYSTEMS ON A TIDELESS COAST
Abstract
The tideless Lake Michigan beach and nearshore zone is a highly complex region in which the energy from wind, wind-waves, and longshore current is dissipated. This energy dissipation results in the generation of these process-response systems which produces topographic variations within the beach and nearshore region. A field investigation was conducted to identify and quantify the dominant process-response systems active on a tideless Lake Michigan beach and nearshore zone. Three data sets of beach and nearshore bathymetric profile data; long term (order years), annual (order months), short term (order days) were analyzed using the method of empirical eigenfunctions. Analysis of the annual data set results in approximately 95% of the variance being accounted for by the three eigenfunctions with the corresponding three highest eigenvalues. The largest eigenvalue corresponds to an eigenfunction called the mean nearshore-beach function, which represents the mean of the data set and is nearly invarient with time. A second eigenfunction, outer-bar function, has a large maximum and minimum in the region of the outer-bar crest and trough. A third eigenfunction, inner-bar function, has a large maximum and minimum in the region of the inner-bar crest and trough. Analysis of the long term data set results in the identification of two dominant eigenfunctions. The eigenfunction with the highest eigenvalue, mean nearshore-beach function, represents the mean of the profile set and is nearly invarient with time. A second eigenfunction, outer-bar function, has a temporal variation which correlates to the annual lake-level variation (order years). Analysis of the short term data set results in the identification of two dominant eigenfunctions. The eigenfunction with the highest eigenvalue, mean nearshore-beach function, represents the mean of the data set and is nearly invarient with time. A second eigenfunction, inner-bar function, has a temporal variation which correlates with the passage of local storms (order days). As a result of this analysis a model has been established which relates long term variations in lake-level to adjustments in the beach and nearshore profile.
Degree
Ph.D.
Subject Area
Oceanography
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