물 개혁에서 빗물 인프라가 뒤처질 것이라는 우려

Auckland Council's head of flood response says recent reform of water services has focused on wastewater and drinking water, and stormwater has often been treated as "the poor cousin".

Flooding in the Wellington suburb of Mt Cook.
Photo: SUPPLIED

Auckland Council's head of flood response says he is concerned stormwater infrastructure is going to be left behind in the three waters reforms.

Parts of Wellington remain in cleanup mode after a record deluge last week and the council is helping some 40 families and individuals find temporary accommodation as their homes have been labelled uninhabitable.

Auckland Council's general manager of Healthy Waters and Flood Resilience, Craig McIlroy, has led a programme using fields, widening streams and other nature-based solutions to managing flooding.

He told Nine to Noon recent reform of water services has focused on wastewater and drinking water, and stormwater has often been treated as "the poor cousin".

"We've got the situation at the moment that these new water entities have been set up, but they've got major major wastewater and water challenges. And my concern at the moment is that stormwater is probably going to be the poor cousin for a few more years yet because while it's part of a big three waters entity, there's no way that the stormwater side of the operation is going to get that same attention as water and wastewater on day one."

Craig McIlroy.
Photo: RNZ / Lucy Xia

McIlroy said Taumata Arowai, who is the technical regulator of water currently has stormwater as its third priority, and the Commerce Commission, who is the economic regulator, doesn't even mention stormwater on its website.

With public concern around flooding high, there is now a once-in-a-lifetime opportunity to develop regional stormwater entities that could follow the model that has worked in Auckland, McIlroy said.

"Providing the community with a really reliable and resilient stormwater network going forward is something that the community is going to demand.

"I would rather think that stormwater could be managed differently by maybe looking at how the type of model that's been applied in Auckland through Healthy Waters and Flood Resilience. I personally think needs replicating across different regions in New Zealand."

Currently the district councils manage urban stormwater, while the regional councils manage rural stormwater, and McIlroy said the two organisations need to be "working a lot more closely together in order to come up with the best overall solution for the community."

"The problem we've got at the moment is there are no stormwater standards in New Zealand that have to be applied across the nation and so it's up to every jurisdiction at the moment to apply their own standards."

McIlroy called for a document which sets out both technical and customer standards, which "everyone" signs up to.

McIlroy said there needs to be a new way to manage stormwater because "building bigger pipes won't work."

With rain events and flooding seemingly becoming more common for parts of the country, McIlroy said "we're facing an entirely new future where quite frankly the history is almost irrelevant."

Flooding in the Auckland suburb of Wesley, January 2023.
Photo: RNZ / Cole Eastham-Farrelly

McIlroy said while wastewater and drinking water were "pipe networks", stormwater needs somewhere else to go when the pipes are blocked or full, which is what happens during heavy rain events.

"The problem with pipes is they're very prone to blockage and the minute you get a big event you get lots of rubbish and dead debris that's in the community that gets washed into drains, ends up blocking pipes, end up blocking culverts. So even if the pipes have a theoretical capacity, the reality of these events is that the pipe capacity is not going to be available to you."

McIlroy suggested looking to "pre-European times and think about how nature designed land to work," but currently developers "pipe all the natural streams to create as much land as possible to build on, and of course that defeats the purpose of how we manage stormwater in a sensible way."

He said natural solutions had to be at the forefront of stormwater strategy now by developing "blue-green networks".

"A blue-green network is where you take an existing situation, mostly it'll be an existing stream but it could be an existing pipe as well, and you create a new waterway by either daylighting the pipe and creating a stream in its place, or taking an existing stream and increasing its hydraulic capacity by making it deeper and wider.

"The idea is that the green bit that sits alongside the stream in a very extreme event becomes blue because that's where we want the water to go."

McIlroy said existing parks in established suburbs can co-exist with proactive stormwater management, and in the Auckland rain event of 2023, the suburb of Northcote provided a good example of how it works.

"There's a playing field that's a part of a community and it's designed to flood in an extreme event and it did in the January 2023 event, it did flood within 24 hours it was green again and so that's the type of approach that we need."

McIlroy said to manage stormwater there needs to be appropriate zoning and land use controls in place, and councils need to plan for a "worst case scenario and then work backwards from that situation to see what is affordable in the community."