Large shallow inlets and bays are complex systems interlinking the terrestrial and aquatic environments and composed of an interdependent mosaic of subtidal, intertidal and surrounding terrestrial habitats. Several of these habitats types are proposed as Annex I interests in their own right. Large inlets and bays are large indentations of the coast, generally more sheltered from wave action than the open coast. They are relatively shallow, usually averaging less than 30m in depth.

Rias and voes are formed through fluvial erosion, whereas fjords evolved through glacial action. These significant differences in development result in various characteristic natural structures forming within the systems. Fjords tend to have a shallow seawards rock sill which causes uneven distribution of salinity throughout the feature. In contrast, rias, with constant seaward gradients throughout, tend to have evenly mixed salinity levels. This mixing of water bodies, as with estuarine systems, is an important characteristic of inlet and bay features.

In many tidal bays and inlets the upper intertidal area contains areas of mobile mudflats, perhaps with a landward wetland fringe. This stratification of habitats within the inlet and bay system can also be seen in the sediments which form the bed of the system. Generally, the sediments will grade seawards into silts, sands and even gravels. This differentiation of sediment bed is an important consideration as different sediment types may vary in their vulnerability to disturbance.

The description of sedimentology, benthic communities and disturbance under other feature headings in this section are also relevant to inlets and bays.

The tables below summarise the potential threats to inlets and bays from land and waterborne processes.

Water based processes

Land based processes

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