Coastal climate change and sea-level rise (SLR)
Hazard risk is compounding in low-lying coastal areas of New Zealand, because hazard events are occurring more often (on the back of a rising sea), while at the same time coastal development and property/infrastructure values are increasing.
Since the late 1880s, sea level has been steadily rising around New Zealand at an average of nearly 1.8 mm per year (18 cm per century). This is similar to the global average rise determined by the Intergovernmental Panel on Climate Change in the IPCC 5th Assessment Report.
Ongoing climate change will lead to some changes to waves, storm surges, salinity and coastal groundwater levels, but the main impact will be from increasing sea level, which will continue to rise for several centuries (IPCC 5th Assessment Report). The uncertainty in future SLR projections is mainly around the rate at which sea level increases, which also depends on how soon global carbon emissions can be effectively reduced.
Accommodating uncertainty in the rate of SLR will be a critical part of land-use planning and engineering design of infrastructure for our coastal margins – both for planning new (“greenfield”) developments and the more problematic challenge of adapting existing coastal development to the rising seas.
Guidance for local government and communities on managing the rising coastal risks and developing adaptation plans are available from the Ministry for the Environment (2017 Coastal hazards and climate change guidance for local government, Preparing for coastal change: A companion to coastal hazards and climate change, and Preparing for coastal change fact sheet series) and the Department of Conservation (NZCPS hazard policies implementation guide-TBD).
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