National and regional risk exposure in low-lying coastal areas. Areal extent, population, buildings and infrastructure. Technical Report
- Author
- R.G. Bell, R. Paulik, S. Wadwha
- Editor
- NIWA
- Year
- 2015
- Journal / Source
- Report prepared for Parliamentary Commissioner for the Environment
- Publisher / Organisation
- NIWA Client Report No.
- Number
- HAM2015-006
- Month
- October
- Keywords
- climate change, sea-level rise,
- Summary
- The mean level of the sea is rising globally due to climate change from a warming atmosphere. Over the past century up to present, New Zealand’s average rise in mean sea level has been similar to the global-average rate – therefore future projections of global-average sea-level rise are generally applicable to Aotearoa–New Zealand (A-NZ). In tandem with this rise in sea level, the frequency of coastal storm inundation has increased (Stephens, 2015), as evident in Auckland such as Tamaki Drive, with the occurrence of these events set to escalate as sea-level rise accelerates. Planning for both coastal erosion and inundation and climate-change effects is a hotly-contested space for vulnerable communities and their councils and requires a sound evidence base built around the timevarying risk exposure. Against this backdrop, NIWA was commissioned by the Parliamentary Commissioner for the Environment (PCE) to provide a nationally-consistent coastal risk exposure as a first pass assessment at the national level, aggregated up from a comparison of results at the regional level. The analysis in this Report is the first consistent attempt at quantifying the risk exposure in low-lying coastal areas across A-NZ and enabling a comparison between different regions and urban areas to assist in prioritising national and regional effort in adaptation to more frequent coastal hazard impacts. Risk exposure is expressed as counts of normally-resident population, land-cover, land parcels and built assets (e.g., buildings, roads, railways, coastal structures) present within various elevation bands up to 3 metres above the present-day mean high water spring (MHWS) tide mark, along with replacement costs for buildings in New Zealand dollars as of 2011 (extracted from the NIWA/GNS Science RiskScape asset database – see Chapter 5). Data on these risk receptors have been have been extracted from Statistics NZ (2013 Census), Landcare Research Landcover Database, Land Information NZ Data Service and RiskScape (NIWA and GNS Science).