Nott, Jonathan, and Hubbert, Graeme (2005) Comparisons between topographically surveyed debris lines and modelled inundation levels from severe tropical cyclones Vance and Chris, and their geomorphic impact on the sand coast. Australian Meteorological Magazine, 54 (3). pp. 187-196.

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Abstract

Comparisons of topographically surveyed debris lines and modelled inundation levels from two very intense cyclones in Western Australia (WA) show close agreement. The largest differences between model predictions and surveyed debris occurred where wave run-up did not overtop the frontal sand dunes and was registered in the coastal landscape. Excellent agreement was found where dune overtopping occurred, as the debris largely represented the height of the storm tide. The post-event field surveys also showed a clear relationship between the height of the inundation (about 7m in one instance), the height of the coastal sand dunes, and the extent of erosion of those dunes. Dunes were eroded vertically, and completely removed, where they were overtopped by the marine inundation (including wave run-up). Horizontal erosion or scarping and landward retreat of the dune occurred where the inundation was well below the dune crest. These observations are significant for policies on set-back distances and minimum habitable floor levels of coastal developments. The results show that these standards need to be above the level of the marine inundation, not the storm tide or storm ‘still water’ level, otherwise buildings erected on filled land behind frontal dunes could be undermined through wave attack and experience structural failure. The field observations and model comparisons of the components of these marine inundations in Western Australia provide confidence in estimates previously used to ascertain the intensity of prehistoric tropical cyclones. The proportion of wave run-up on much less permeable and smoother surfaces (sand versus gravel and coral shingle) was considerably less than that used for estimates of prehistoric cyclone intensities, suggesting that wave run-up may play a less important role in constructing long-term sedimentary records of tropical cyclones.

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