Coastal hazard assessment from multidecadal profile response incorporating climate patterns and sea-level rise
- Author
- Skinner, W. K.
- Year
- 2024
- Journal / Source
- Journal of Coastal Research
- Volume
- 40
- Number
- 3
- Pages
- 511-526
- Keywords
- Papamoa
- Summary
- A new method for coastal hazard assessment is described and demonstrated by reference to a 40-year cross-shore profile record in Papamoa, New Zealand. It is based on a mathematical interpretation of the envelope within which long-term historic cross-shore profiles vary and from which, for the required assessment period, the statistically significant fully accreted-state and fully eroded-state profiles can be determined. The Monte Carlo method is used to derive stochastic outcomes for long-term trend (LTT) and sea-level rise (SLR) on the basis of correlations with, and a long term proxy for, a decadal-scale climate pattern, which in the example case is the Interdecadal Pacific Oscillation. Sediment volumes for short-term fluctuation and the LTT are determined and conserved to reflect a consistent wave climate over the assessment period when appraising the effect of SLR. Dune biomass is accounted for when determining erosion scarp stability and hence the final extent of the current and future hazard zones. Results are presented in schematic form as excursions relative to a land benchmark and also as full end-state profiles extending from the dune backshore to the closure depth, with the latter determined by bar volume and profile. Various scenarios are appraised, including those that incorporate SLR predictions of the climate models of the Intergovernmental Panel on Climate Change. The relative risk of various scenarios is benchmarked to the probalistic expected outcome to produce a risk-based, site-specific assessment of coastal hazards.