Lord howe island - unique coastal processes and challenging coastal management

Haskoning Australia was engaged by the Lord Howe Island Board to undertake a coastal hazard definition and coastal management study for the island. In this paper, some of the interesting coastal aspects of the island are described, to emphasise how unique it is compared to the NSW mainland. Issues such as wave climate, coral reef effects and sedimentation, water levels, legislation and datums are considered. The island is exposed to a larger and more westerly wave climate than mainland NSW, but partially sheltered by a coral reef (which is probably supplying a small amount of sediment to an adjacent lagoon) on its western side. The response of the reef under climate change (sea level rise and acidification) is critical in terms of potential future erosion/recession. There can be large shifts in mean sea level in the lagoon in response to shifts in wave direction, and oceanographic effects. Mainland NSW legislation has limited application on the island, and Australian Height Datum does not have its mainland (mean sea level) meaning there. A key challenge is to manage the coastal risk to infrastructure (including a road) on the western side of the island, in the context of the economic and environmental constraints that apply.