The Ministry for the Environment released an updated Coastal Hazards and Climate Change manual for local government last week, based on work done by NIWA. It incorporates the latest NZ thinking on where sea-levels are heading. If you’re planning to build something that has to last until the end of the century (and that covers a lot of coastal infrastructure), you should allow for half a metre of sea-level rise, and consider the consequences of an increase of up to 80cm. The report says:
For planning and decision timeframes out to the 2090s (2090â€“2099):
a. a base value sea-level rise of 0.5 m relative to the 1980â€“1999 average should be used, along with
b. an assessment of the potential consequences from a range of possible higher sea-level rises (particularly where impacts are likely to have high consequence or where additional future adaptation options are limited). At the very least, all assessments should consider the consequences of a mean sea-level rise of at least 0.8 m relative to the 1980â€“1999 average.
For planning and decision timeframes beyond 2100 where, as a result of the particular decision, future adaptation options will be limited, an allowance for sea-level rise of 10 mm per year beyond 2100 is recommended (in addition to the above recommendation).
Local authorities have a duty to understand this stuff (under the RMA and other legislation), so the report is highly detailed. If you’ve ever hankered after an in-depth understanding the processes that underlie storm surges, beach (and bach) erosion, tidal ranges and tsunamis, there’s no better place to start. If you want to see what impact that sort of rise might have on your area, try Global Warming Art’s excellent Google Maps mashup Sea Level Rise Explorer, or check NASA JPL’s new climate change site for the global sea level picture [Flash required].
Also released last week: the edited highlights (with pretty pictures) version of the Preparing For Climate Change guidance manual published last May which incorporates NIWA’s latest climate projections for NZ. Essential. And free.