Historical shoreline response to inlet modifications and sea level rise (M.S. Engineering Thesis)

Abstract

This thesis examines the historical shoreline response to inlet modifications and sealevel rise. Inlet modifications are considered to be the geographic stabilization and training(through the use of structures) of natural inlets and the creation and further modification ofartificial inlets. Shoreline response to natural and artificial processes must be understood inorder to predict the performance of the coastline. The tendency for creating and modifyinginlets increases as industry and population growth demands. Sea level rise is a natural processwhich cannot be controlled at this time. Current theoretical approaches to predictingshoreline response indicate that sea level rise and inlet modifications can cause substantialshoreline impact. Florida, with roughly a century of shoreline position and relative sea leveldata, provides a basis for examining past trends and comparing them with theory.The shoreline of Florida was found to be accreting with the greatest accretion alongthe east coast. Shoreline responses within the boundaries of the erosional influence of inletsdue to their creation and/or modification were examined for 19 inlets around the coast ofFlorida. The differences in the shoreline response before and after the initial modification ofeach inlet show the erosional strain that inlets apply on the nearby shoreline. The effect onshoreline response due to the human intervention (unnatural processes) of modifying inletswas isolated and examined. The shoreline response due to this "human intervention" was erosional, thereby showing the negative impact that modified inlets have on shorelines. Thisinduced erosion is responsible for the loss of roughly 21.6 million cubic yards of sand from theshoreline that is within the erosional influence of Florida's east coast inlets. Combining theshoreline changes due only to natural processes with sea level rise data allows for comparisonwith the commonly accepted Bruun Rule for shoreline response as a result of a changingsea level. This comparison and the effects of including a lag time between a rise in sea leveland a change in shoreline along the east coast of Florida during the last century show noagreement with the Bruun Rule and no correlation with a specific lag time. (153 pp.)