Practical applications might yet range from selective use of green roofs for absorbing water to placing houses on stilts and orderly withdrawal from some areas, but much could depend on political willpower and finance.
A report presented for today’s Dunedin City Council meeting provided four case studies: schemes to raise houses above likely flood levels in New Zealand and Australia; residential retreat in Christchurch after earthquakes there; a development in Long Bay, Auckland, described as environmentally responsive; and a comprehensive programme in Copenhagen, Denmark, to enable the city to cope better with intense rainfall.
The case studies could help planners arrive at a blend of solutions or compromises.
The report, led by WSP, was described as a supporting document for a proposed initial long list of 16 generic possible approaches to help South Dunedin adjust to rising groundwater and increasing vulnerability to natural hazards.
Copenhagen was hit by a deluge in 2011 and the city’s infrastructure could not cope.
That led to adoption of a cloudburst management plan that included staggered introduction of various projects, an experimental neighbourhood where innovative or local solutions were tried, floodable parks, drainage improvements and planted rooftops to absorb rainfall.
WSP said the case study showed how a suburb could be "retrofitted" to better withstand rainfall-induced flooding.
"It also highlights the importance of community engagement and allowing the community to contribute and test ideas that can then be implemented."
WSP said a mosaic of solutions could be useful in South Dunedin.
Allowing certain areas to flood, resulting in decreased flooding in other areas, was another technique that could be applied and "green roofs could be selectively implemented in South Dunedin".
Raising houses by installing new support piles is an approach to be tried at Gisborne after damage from Cyclone Gabrielle last summer.
It is also being used in Queensland, Australia, where a resilient homes fund was set up last year.
WSP said it could be useful as a medium-term adaptation option in locations where retreat might be necessary in decades to come.
"Blended finance and cost-sharing by different tiers of government, insurers and homeowners can help overcome financial barriers."
Christchurch, after the 2010 and 2011 earthquakes, was presented as New Zealand’s largest-scale example of residential relocation.
Some areas were deemed off-limits for rebuilding and there was a buy-out scheme.
WSP noted some residents had trouble finding suitable housing to relocate to and some areas experienced population increase without adequate roading and utilities.
One applicable lesson was "the true power of the recovery is held by the level of government that controls the flow of money".
It was considered a buy-out scheme had potential for flood-prone areas and could be applied gradually.
Long Bay, on Auckland’s North Shore, was an example of urban design that worked with the natural environment.
Man-made wetlands were added into Long Bay’s design to retain stormwater.
Such improvements happened there before the land was developed.
