BEACH DYNAMICS AND THE SOCIETAL RESPONSE TO BEACH EROSION AT MARCO ISLAND, FLORIDA

by REYNOLDS, WILLIAM JEROME, Ph.D., Rutgers The State University of New Jersey - New Brunswick, 1982, 362 pages; AAT 8305775

Abstract (Summary)



Aerial photo and field analysis of coastal processes at Marco Island shows the island shoreline exhibits distinct differential movement. The northern and southern ends of the island have experienced the greatest changes. The southern terminus has suffered significant erosion whereas extreme erosional and accretional fluctuations have occurred on northern beaches.



An air photo analysis shows that movement rates based on 1926 and 1981 photos differ radically from trends based on shorter time intervals. This indicates that mobility rates calculated from photos separated by extended time intervals may completely blur actual shoreline movement and lead to faulty conclusions regarding movement magnitude and direction.



A sediment budget was performed using the areal polygon method based on photo coverage of seven of the ten years from 1971 to 1981. This study detailed sediment movement between Big Marco Pass and Caxambas Pass and determined the net annual average littoral drift to be 26,400 cubic yards to the south. Gross annual drift generally differed from net annual drift by an order of magnitude.



Societal response to beach erosion on Marco Island has taken both structural and nonstructural form. Since shoreline development began in 1966 structural response has been incremental, with each structure progressively more substantial than its predecessor. Comparison of the air photo analysis and structural response study shows that two of the three structural response sites are located on historically accretional shores. Inference may be drawn that these accretional shores were transformed into erosional ones due to imprudent placement of landscape walls and bulkheads, resulting in a partially engineered shore and near total localized loss of the recreational beach.



Comparison of the shorelines of Marco Island and Naples, Florida reveals distinctly different cultural landscapes, attributed to the different time of development and the consequent different philosophy in shoreline protection. The coastal landscape is found to be a cultural artifact, reflecting the period of shoreline development. A Marco Island Model is represented as a prototype for future barrier island development, or redevelopment.