Coastal Restoration Trust of New Zealand

Coastal Dune Ecosystem Reference Database

New Zealand Archaeology

Golson, J.
A Coastal Sensitivity Index (CSI), based on an initial framework for physical coastal hazards information, is described including it's development and application. The CSI provides a standardised method for assessing the relative sensitivity of areas of the New Zealand coastline to selected physical processes that may become natural hazards. CSI's are derived by numerically integrating 8 variables which include elevation, maximum storm wave run-up level, gradient, maximum tsunami wave height, lithology, natural landform, horizontal shoreline trend, and short-term shoreline fluctuations. Each variable representing the end effects of many interacting processes is ranked into 5 sensitivity classes (1 to 5) in a matrix and a specific CSI is derived by adding the class allocated to each of the 8 variables for a coastal site. CSI's potentially range from a minimum of 8 (very low sensitivity) to a maximum of 40 (very high sensitivity), the classes ranging from very low (8-13), low (14-20), medium (21-27), high (28-34), to very high (35-40). During the development and standardising of the technique 113 field sites were tested, representing the diversity of open-exposed to sheltered estuarine and harbour coastlines. For all these sites good quality data were available, demonstrating that the internally consistent CSI technique may be confidently applied to most coastlines provided reliable, professionally defensible information exists for each of the 8 variables. Coastlines with very high CSI's are typically low-lying coastal landforms of unconsolidated sediments with a history of shoreline retreat, high to very high shoreline fluctuations, and inundation from storm wave run-up and tsunami. Coastlines with very low CSI's are typically hard rock landforms of steep elevation, with a history of low to very low shoreline movements and inundation from the sea. The technique is rapid and cost effective, providing a mechanism for achieving national consistency whilst accommodating local and regional variations.
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