Water infrastructure in jeopardy
Much of the country’s wastewater and stormwater infrastructure is unprepared for the strain of climate change, which could lead to more floods like the one that devastated Edgecumbe - unless hundreds of billions are spent.
This is the finding of a report from the Deep South National Science Challenge, released today, which warned that, if action was not taken, communities could expect more water outages, contamination and sewage overflows.
Environmental planner Iain White, who co-authored the Climate Change and Stormwater and Wastewater Systems report, said ageing infrastructure was expected to face more extreme rainfall events, storm surges, sealevel rise and drought as the climate warms.
The Edgecumbe floods in April were a wake-up call for how unprepared some systems were, White said.
After heavy rain brought about by Cyclone Debbie, the stopbank protecting Edgecumbe from the Rangita¯iki River burst, flooding the town and leaving raw sewage floating in the streets.
Six months on, 500 houses were still unliveable and flood-proofing remained a distant goal, White said.
Existing infrastructure had been designed with last century in mind, and without upgrades Kiwis should expect failures more frequently, he said.
‘‘We are going to have to invest in bigger pipes, which are more expensive ... we are going to have to change how we fund our infrastructure,’’ White said.
‘‘We are going to have to invest in bigger pipes, which are more expensive . . . we are going to have to change how we fund our infrastructure.’’
Iain White, environmental planner
‘‘If we want things to stay the same, we will have to change.’’
Most of the country’s stormwater infrastructure was built to handle a one-in-10-year flood. But White said by 2050, it was expected some coastal areas could expect one-in-100-year events on an almost annual basis.
Systems most at risk were those with combined wastewater and stormwater pipes because sudden deluges could cause overflow, putting public health at risk.
Auckland has about 200 kilometres of such piping. In May, the super-city was hit by storms that flooded hundreds of properties and caused hundreds of thousands of dollars in damage.
Pipes in some areas, such as parts of South Dunedin, were only designed for a one-in-two-year floods, leaving it highly vulnerable to flooding as the runoff from the surrounding hills funnels in.
In July, heavy rain infiltrated the southern city’s wastewater system and contaminated water overflowed onto urban roads.
Drawing on contributions from academics, scientists, government policy analysts and service providers, the report identified many areas where research was lacking.
Local Government New Zealand (LGNZ) chief executive Malcolm Alexander said replacing aging 1960s piping and sewers alone could cost up to $100 billion.
Coastal areas were expected to bear the brunt of that because their pipes fed directly into the sea, leaving them vulnerable to corrosion from salt water and the possibility of back-flows as sea levels rose.
In some locations this was already happening, spilling sewage and wastewater onto parks and roads during king tides, according to the report.
LGNZ president Dave Cull said improving waste and stormwater systems was one of the greatest challenges facing councils nationwide.
Doing so would require more support from central government, given it would come at a significant cost, he said.
This year is already the most expensive year on record for insurance claims related to significant weather events, which have hit $230 million, according to the Insurance Council.