ABSTRACT

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 deposition, and then eroding again. A prime factor that is quite pertinent, but seldom considered, is the slower movement associated with tectonics, or isostatic adjustment. Previous studies cite evidence of modern uparching 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 which are the scenes of most severe 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 panhandle of Florida.