Rising seas: Wellington's watery future

Rising tides: A map of areas at potential risk.
Rising tides: A map of areas at potential risk.

Wellywood looks destined to become Waterworld, and the capital needs to face some tough decisions.

The choices include abandoning the CBD and low-lying suburbs such as Lyall Bay and Island Bay to rising seas, or risking a Hurricane Katrina-like flooding disaster behind sea walls.

These questions were raised in a report made public this week looking at how the capital would be affected by a predicted rise in sea levels of one metre over the next century.

But other solutions could see the city transformed into a Venice-like marvel, with Oriental Bay and Seatoun residents living in canal cities or floating suburbs.

The results of the Wellington City Council-commissioned analysis were certain of one thing - hundreds to thousands of properties and billions of dollars' worth of infrastructure were at risk from the encroaching waters.

Several levels of ocean-level rise were modelled in the report, and heights of 0.6m and 1.5m were used as examples to illustrate the variability of the hazard the capital faces.

Although seas of 1m higher were likely in a century's time, expert projections show the waters will continue to rise after that.

If left unchecked, a rise of 1.5m would displace about 2000 residents in large parts of the CBD, Kilbirnie, Oriental Bay, Hataitai, Pipitea and Makara Beach, the report by consultants Tonkin and Taylor concluded. Homes, buildings and underground infrastructure totalling $6.5 billion could be damaged.

The capital would also lose significant landmarks, from old pa sites to the historic Government Buildings, now home to the Victoria University law school.

Should the seas reach just 0.6m above today's levels, the effect on the city would be far less severe, the modelling concluded.

Yet an estimated 150 Wellingtonians from Oriental Bay, Hataitai, Pipitea and Makara Beach would still lose their homes and the city would lose dozens of cultural and environmentally significant areas, such as the Makara estuary.

The infrastructure bill would stand at $400m.

The report details ways the city could prepare for the rising tides.

The council has previously outlined its plans to use "hard" defences, such as sea walls, and "soft" ones such as restored sand dunes. But the report warns that such a strategy could leave the city at risk from a disaster comparable to what New Orleans suffered after its levees broke during Hurricane Katrina.

Council climate change portfolio leader David Lee said the council and community had tough decisions to make now.

"Protection is a first, almost knee-jerk, reaction . . . but we will reach a point where it's not tenable to actually protect, in terms of cost and practicality."

Managed retreat was another suggestion, in which the council could rezone threatened areas to curb development. Residents would move out over the years.

The report also suggests creating or retro-fitting stilted homes and buildings as well as floating cities - "essentially large permanent cruise liners" - although it accepts these would be costly and less realistic.

Roads between buildings and houses could be flooded, turning suburbs into canal communities, with streets replaced by ferry services.

Engineering solutions not yet feasible, such as "water scrapers" starting beneath the sea, could be part of the city in 100 years.

The Dominion Post