Coastline Development and Change in Alabama and the Florida Panhandle

George M. Lamb

Although evidence of sea level rise has caused concern about erosion of the coasts, some coastal areas are accreting. As an investigator approaches a study of any particular stretch of coast, it soon becomes apparent that one problem in determining what is happening, or what has happened to a beach, is the problem of deciding upon a time frame. There are daily, seasonal, and much longer term changes that must be dealt with and understood. On the Alabama coast, there is evidence of both deposition and erosion over relatively long time periods, as well as evidence of cyclical changes. Maps over a 150-year period show steady growth of Perdido Key from Florida into Alabama. Aerial photographs over a 50-year period show an eroded portion of Dauphin Island being built up by dep sition, and then eroding again. A prime factor that is pertinent, but seldom considered, is the slower movement associated with tectonics or isostatic adjustment. Previous studies cite evidence of modern up-arching of parts of the Gulf coastal plain accompanying the well-documented subsidence of the Mississippi delta area. First-order leveling reports indicated that many of the coastline areas that are the scenes of most extensive erosion are areas in which the land is subsiding. Other areas, which are neutral or possibly rising slightly, are relatively free from erosional problems. This latter point is particularly important in understanding the Gulf Coast of Alabama and the Florida Panhandle.

AAPG Search and Discovery Article #91042©1987 GCAGS and GC-SEPM Section Meeting, San Antonio, Texas, October 28-31, 1987.