Sections 2.3 and 2.5 described the classification of coastal systems on the basis of plate tectonic setting and substantial sea-level changes respectively. Superimposed on these large-scale characteristics are regional and local scale variations in coastal landforms. One way to distinguish between features at these scales is to look at the hydraulic boundary forcing to the coastal system; the dominance of fluvial, wave or tidal processes can be seen to influence the shape of coastal features.
A process-based classification on the basis of the relative importance of fluvial sediment supply and wave and tidal action is relevant to trailing-edge coasts (such as the USA East Coast) and to the typical Dutch situation (being an example of a marginal sea system; other ones being the Gulf of Mexico and the Chinese coast).
Such a process-based classification of coastal systems implies that we can distinguish between various characteristic coastal morphologies on the basis of two criteria:
- How important has fluvial sediment input been for shaping the coastal system
- Are sediment deposits being reworked by waves or tides (wave-dominance or tide-dominance)?
Based on the answers to those questions the following systems can be discerned (with the numbers in the list referring to the numbers in Fig. 2.41 and the respective sketches of Fig. 2.42):
- Wave-dominated uninterrupted coastline (or pocket beaches) with tidal influence at the lower shoreface only
- Wave-dominated deltaic (i.e. built out by fluvial sediment supply) coastline
- Deltaic coastline with no significant wave or tidal influence
- Tide-dominated deltaic coastline
- Estuary with fluvial deposits shaped by tide
- Estuary (tide-dominated)
- Tidal inlet system dominated by tide with combined wave and tidal influence at the inlet
- Wave-dominated barrier system