10 - Barrier systems
from Part III - Coastal Systems
Summary
Synopsis
The term barrier is used to describe a range of emergent depositional landforms which are separated from the mainland coast by a lagoon, bay or marsh. The barrier may be composed entirely of cobbles or gravels or, more commonly, they are dominantly composed of sands with minor amounts of gravel, silt and clay. They may be associated with coasts with a strong longshore sediment transport component and often form the sink or downdrift end of a littoral cell or coastal compartment. The lagoon or bay, intertidal flats and marshes that are protected by the barrier are usually highly productive ecologically with marshes and sea grass beds providing the base for a food web that includes a wide range of shellfish, crustaceans and invertebrates, nurseries for fish and habitats for a wide range of birds and mammals.
The barrier itself forms the emergent depositional component of a larger barrier system that includes the nearshore and beach, back barrier sediments and the protected lagoon, bay or marsh landward of it. Barriers have a subaqueous platform or base on which they are built and an overlying subaerial component. The platform is built alongshore and offshore by littoral processes and by sediments washed over the barrier by storm waves. The subaerial component of the barrier consists of the beach and backshore, dunes (in sandy systems) and a variety of back-barrier sediments that are washed over during storms or transported by wind both from the seaward side and from the lagoon or bay.
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- Information
- Introduction to Coastal Processes and Geomorphology , pp. 280 - 324Publisher: Cambridge University PressPrint publication year: 2009