Cooper, J.A.G., Pilkey, O.H., and Lewis, D.A. 2007. Islands behind islands: an unappreciated coastal landform category. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 907 – 911. Gold Coast, Australia, ISSN 0749-0208

The 15,000 plus barrier islands in sheltered or fetch-limited, nearshore marine waters have not achieved recognition as a distinct and important landform. As a consequence, these abundant islands have never been counted, described, measured or otherwise examined in any systematic way. About half of these islands are actively eroding, accreting or migrating in response to modern oceanographic processes, and these are the subject of this study. The other half are inactive islands enclosed by salt marsh or mangroves which are shorter than ocean barriers (average 1 km), but evolve via the same processes. Overwash is almost always the dominant process, while dune building is only important locally.

More than 70% of fetch-limited barrier islands are found on trailing edge coasts where conditions are favourable for formation of sheltered waters under a rising sea level. Active fetch-limited barrier islands are found in estuaries and bays (Chesapeake Bay, USA); behind ocean barriers (Pamlico Sound USA); adjacent to inlets (Tapora Bank New Zealand); rimming deltas (Menderes River, Turkey); eroding thermokarst (Yensei Bay, Russia); and glacial outwash fans (Canal Baker, Chile). Understanding the highly variable processes of evolution of these islands should be a high priority, because sheltered barriers are becoming the next frontier of coastal development. The aim of this paper is to describe the geomorphology of islands within the sheltered settings produced in barrier lagoons, and to discuss the management issues associated with their human occupation and use. Examples from lagoons of the eastern United States and the Gulf coast of Mexico are discussed.