Coastal Environments and Global Change

9 Barrier Systems

Sytze van Heteren

Geological Survey of the Netherlands, Utrecht, The Netherlands

9.1 Definition and description of barriers and barrier systems

In discussing barriers and barrier systems, it is important to consistently distinguish the individual landform (barrier) from multiple inter-related barriers within the context of an overall coastal setting (barrier system).

Barriers are elongated, wave-, tide- and wind-built ridges that are composed predominantly of unconsolidated sand and gravel, and protect the adjacent mainland from open-water processes. Most of them are oriented parallel to the general shoreline trend. Their crests are above high-tide level, distinguishing them from bars. Barriers are potentially mobile, and usually separate marine or lacustrine open-water bodies from marshes, lagoons and estuaries that may be connected to sea or lake by tidal inlets.

Barrier systems are series of barriers and their associated environments along a coastal compartment defined on the basis of a common setting or sediment source. They may contain series of similar barriers, but more commonly include a range of barrier types. On the one hand, barrier systems are a composite of various smaller-scale coastal environments, including beaches (Chapter 7), coastal dunes (Chapter 8), salt marshes and tidal flats (Chapter 10), mangrove shorelines (Chapter 11), tidal inlets and tidal deltas (Chapter 12), and the shoreface. On the other hand, barrier systems are part ...