Pipe problem in too-hard basket

Drainage pipes disgorge water from North Shore properties. Photo / Paul Estcourt

Scores of drainage pipes protruding from the picturesque cliffs of the North Shore are causing erosion and creating an eyesore, but an answer to the problem will have to wait until the Super City is formed, a councillor says.

"All North Shore's east coast cliffs have a serious erosion problem because of stormwater discharging down the face of soft sandstone cliffs and speeding and collapsing those landforms," Auckland Regional Council member Joel Cayford said.

The plastic pipes, which were installed legally, bristle from cliff-top perches of some of Auckland's most expensive homes, and while the owners might not notice them, people wandering below do, Mr Cayford said.

"You might be happily sitting in your home above the cliff and not seeing the pipe but everybody on the beach can see it as an eyesore."

North Shore City Council had failed to stop the pipe drains and owners from building close to the cliff, he said.

"Those properties need to hook up to the council stormwater drain and withdraw from the clifftop. The Super City will need to address it."

City councillor Tony Holman said some pipes could be removed only by a new law.

"It's going to cost lots of money," he said.

"Engineers and planners must come up with a more environmentally appropriate solution. We must provide a line beyond which people cannot develop because the district plan is not robust enough to protect the coastal area."

The council could not identify Browns Bay properties using the pipes in photographs taken by the New Zealand Herald, but said the pipes must have been installed before 2002.

Rules now required stormwater outlets to be thrust through the cliff to an outfall at its base.

Stormwater operations manager Frank Tian said the pipes were legal.

"We don't have the legal power to do anything," he said.

The first choice was to connect pipes to the public drain.

But if the slope was too great to let stormwater siphon, the discharge pipe must be hidden in the cliff and diffuse the energy of the falling water on to the beach.

Erosion was also caused naturally by waves and weather.

North Shore's district plan has varying "foreshore yard rules" for the coastal protection area where homes can sell for $8 million plus.

But although the council, with the ARC, has researched the need for stricter controls, it has not introduced them.

Engineer Steven Price, of Riley Consultants, said the increasing value of cliff-top properties made building large protection structures more economic.

Larger dwellings were being built with a smaller setback from the cliff top than structures built 50 years ago.

This meant protection structures, such as in-ground walls, were needed to ensure ground under and around the structure would be there in 100 years.