Physical Environment of the West Coast Coastal Marine Area
2.2 West Coast in the New Zealand Marine and Coastal Context
The West Coast coastal marine area that is under consideration by the West Coast Marine Protection Forum lies between Kahurangi Point in the north and Awarua Point in the south. This coastal and marine environment extends for some 600 kilometres along the windward side of the South Island out to the 2 nautical mile limit, and is the area described in this report in terms of its physical and biological features and its human uses (see Figure 2.2). The Forum is aware of an alternative boundary that proposes 2 nautical miles or 200 m depth (whichever is closer to shore). The West Coast marine and coastal environment has a number of physical features which, in combination, distinguish it from other New Zealand coasts. In particular, it is very exposed to prevailing westerly winds and high energy wave action. Other distinguishing physical features include: the pronounced effects of sedimentation (including glacial sediments and sand scour), its dynamic shelf and river hydrology, and spectacular coastal landscapes (within a setting of a mountainous hinterland), which include many headlands and an extensive network of relatively unmodified tidal wetlands. |
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Recent studies have shown that the West Coast marine environment shares many biological characteristics with other South Island coastal regions, in respect to fish6 and algae7. Nevertheless, a number of physical features make the West Coast clearly different from:8
- the North Island west coast (because of the West Coast’s more southerly latitudes, hydrography and geology);
- the Fiordland coast (because of the West Coast’s lack of sheltered inlets, the dominance of sediments on its beaches and broad continental shelf);
- the South Island east coast (because of the West Coast’s exposure to prevailing westerly storms, higher rainfall and sedimentation, including glacier derived sedimentation, and its very different geology);
- the Stewart Island/Rakiura coast (because of the prevalence of mobile sediments on the West Coast); and
- the greater Cook Strait coasts (between Farewell Spit and Taranaki) (because of the West Coast’s higher exposure to westerly waves and absence of sheltered bays).
These physical differences have a major bearing on the biological features that are found in the West Coast marine and coastal environment. For these reasons, a draft national nearshore marine classification system being developed within the MPA Policy framework9 considers the West Coast to be a distinct marine ecological region, with features that are not represented elsewhere in the country (nor indeed the rest of the world).
 Many large rivers, like the Haast, carry high loads of suspended sediments to the beaches and seafloor of the West Coast. Photo: T. Hume, NIWA. |
 The West Coast marine and coastal environment is very exposed to high energy waves. Photo: S. Nimmo. |
6 Francis1996
7 Adams 1994
8 Neale & Nelson 1998
9 Walls 2006