Underwater waterfront: How city may look

Photo / Richard Robinson

New interactive maps have shown how projected sea-level rise under different climate change would transform our coastlines and inundate low-lying areas.

The maps have been produced by US news organisation Climate Central in tandem with projections published last month in the journal Proceedings of the National Academy of Sciences.

They allow users to view how sea levels could change in scenarios where average temperatures were 2C and 4C higher by 2100, with the latter showing low-lying land areas around the Auckland and Waikato areas including Port Waikato, the Hauraki Gulf and the Kaipara Harbour inundated with water.

Other parts of the city, including Wynyard Quarter and Tamaki Drive, are also shown as underwater in a 4C scenario.

The timeframe for the coastal changes displayed in the maps is wide - from less than 200 years to as long as 2000.

Niwa scientist Rob Bell said the maps needed to be viewed with some caveats.

Global data used in the projections was less accurate for New Zealand than that now used by councils and could generally under-estimate the risk, while other aspects could be over-estimated.

"In short, these type of global interactive map tools provide a general indication of areas that may be affected at different rises in sea level, but are not appropriate for basing planning or infrastructure decisions on," Dr Bell said.

According to projections, the mean temperature in New Zealand could reach 2C higher by 2100 if emissions are able to be limited - or between 3C and 4C higher if no action was taken.

Within the same period, sea level is expected to rise between 50cm and 100cm, leaving populations to adapt by abandoning coasts and islands, changing infrastructure and coastal zones, or building barriers or dykes.

A report released last year by the Parliamentary Commissioner for the Environment warned that sea levels could rise 30cm around the country by 2050, while severe flooding like the storm surge in January 2011 that inundated downtown Auckland would be occurring every decade.

Commissioner Dr Jan Wright is set to publish a major new report on sea-level rise next week.