Suggestions for flood-prone areas
A visiting expert on landscaping flood-prone city zones recommends Christchurch use natural barriers and water-based construction to deal with rising sea levels.
Landscape architect Kristina Hill from the University of California, Berkeley, spoke at a public meeting organised by Regenerate Christchurch on Thursday night.
She presented research-based ideas that could be implemented in the city’s planning for flood-prone coastal areas and the residential red zone.
Eastern areas of Christchurch sank in the Canterbury earthquake and the Christchurch City Council has identified many residential zones as prone to flooding and sea level rise over the next 100 years.
Hill encouraged the city to experiment and accept that some ideas might fail.
‘‘That’s how the Dutch have become the world’s consultants on flooding, through trying things.’’
She spoke about different ideas of terraced developments.
One design used in Hamburg, Germany, was multi-level residential buildings with waterproof lower levels. In extremely high tides the water rises over footpaths and public areas and vehicles are protected in waterproof car parks. ‘‘People don’t evacuate. They stay and they watch the flooding happen with their kids.’’
As well as removing the need for costly and disruptive evacuations, Hill said it also provided an educational experience.
Another concept was the idea of using wetlands and developed stormwater ponds to hold back the sea. It was simple, Hill said: ‘‘Dig hole, make mound.’’
Silt dug out from stormwater ponds near the sea would be used to create wetlands, pushing the open water back to sea.
Floating houses would be built on the ponds, aimed at the highend of the market similar to Dutch developments.
The added benefit would be that stormwater would drain from surrounding lower-income areas into the ponds.
Hill called it a ‘‘Robin Hood strategy’’, getting the rich to pay for wider benefit.
Water would be collected in the city, filter into the ponds, and be released through the wetlands into the sea.
The wetlands would also create habitats for wildlife, she said.
As the sea level rises over time, ponds could be moved further inland, turning the old ponds into more wetland.
‘‘It seems to me that your estuary will be a great place to try some fo these wetland terrace ideas,’’ Hill said. ‘‘We know that this is all really happening to us, so we are trying to take a positive, proactive approach to it.’’