Disintegrated coastal zone management (DICZM): an example from Auckland, New Zealand

Typically, integrated coastal zone management (ICZM) uses the informed participation and cooperation of all stakeholders to assess the societal goals in a given coastal area. ICZM seeks, over the long term, to balance environmental, economic, social, cultural and recreational objectives, all within the limits set by natural dynamics. We outline coastal instability in the Auckland region of New Zealand, where the effects of natural coastal dynamics appear to have been underplayed, or even overlooked, during the residential land development process. Auckland is New Zealand’s largest city, with the Auckland region encompassing c. 3,300 km of coastline, with a highly variable wave climate and coastal geomorphology. The sparsely inhabited high energy west coast records significant wave heights of 2-3 m for much of the year. In contrast, the eastern bay coastlines are lee coasts, protected by offshore islands in the Hauraki Gulf and the Coromandel Peninsula. Nevertheless, significant coastal cliff instability does occur along these eastern coasts, which are heavily populated, with houses often constructed within 10 m of the cliff edge. Coastal instability in the Beachlands area in particular, is part-conditioned by engineering properties of the cliff materials, which include soft, Pleistocene sediments. In particular, shear surfaces develop along clay-rich tephra layers, which are of low-permeability, leading to increased porewater pressure, and cliff failure.  Despite the clear failure mechanisms, coastal protection works and routing of domestic stormwater over the cliffs has led to further coastal instability.