Stormwater stream for future development

A proposed stormwater plan to get rid of water quickly from future development in Richmond South all the way to the Waimea Inlet will be a naturalised, meandering stream with space to cater for floods.

The Richmond Stormwater Upgrade Programme will follow the general path of the existing Borck Creek which flows from the Richmond Ranges, under Main Rd Hope and curves around the Waimea Plains to the redeveloped creek between Berryfields and The Meadows.

Tasman District Council’s team leader of project managers, Rob O’Grady, says the completion of the stormwater channel will take years as the council works through land purchases and finishes the design work.

The channel is designed for a one-in-a hundred-year flood, and he says the higher-intensity of storms and scale of flooding seen in recent times has prompted a larger-scale project which requires more land than the original design.

Much of the existing waterway is highly modified, often to straight drains with little habitat for fish or birds. Plus, Rob says it is just not big enough for the expected urban development south of the town.

The proposed waterway will have green space up to 70m wide in some places to cater for potential floods so that water is quickly taken away and out to the estuary. He says width will depend on the gradient of the land, becoming wider as the gradient lessens.

“The philosophy is we want to match the natural contours of the land. The water goes where it wants to go, and the better we can keep it to where it wants to go, the better off we are.”

The end result will be similar to the stream that runs alongside Headingly Lane which has plantings beside the water.

Wider green spaces with no vegetation beyond the stream is aimed at allowing floodwaters to flow unimpeded. Likewise, the Borck Creek redevelopment between Berryfields and The Meadows follows that design and he says that area has been designed to cater for future development in the catchment.

The design recognises the principles of Te Mana o te Wai and is a requirement in the National Policy Statement on freshwater. It also needs to meet the legislative changes that have been introduced since the council’s first stormwater plan for the area.

So far, the council has been negotiating with about 20 landowners and has already purchased some properties, though he says there have been a range of responses.

He says the council prefers to work on a willing buyer, willing seller basis, but acknowledges some land may have to be purchased through the Public Works Act. More land may yet be required for the stormwater upgrade, depending on rezoning through the Future Development Strategy (FDS).

The proposed Richmond South development for example, has plans for 2,000 houses in Hope and it has made it as far as the FDS, but Rob says it may end up as a higher-density subdivision to cater for population growth. What happens with zoning between that Richmond South subdivision and Richmond will also affect the eventual design of the stormwater channel.

Development leads to an increase in impervious surfaces such as roads, roofs and driveways, so instead of water being soaked into the ground, it creates an increase in stormwater runoff heading into streams.

Bridges are included in the design including a sizeable bridge on Main Road Hope, State Highway 60 and at Lower Queen St beside Headingly Lane. The latter will be a replacement of the existing bridge to widen the bottleneck of the stream at that point.

While the stormwater channel is necessary for future growth, Rob says the council is mindful that it is dealing with people’s homes and livelihoods when it requires land for the project. He says the council cannot give absolute answers to many landowners until the FDS and the stormwater design are further down the track.

“There are many parts of the jigsaw to be solved yet. Until we get it all in the right order, we can’t leap ahead.

“We’re open to talking to people (landowners) if they have concerns and it is very much a case-by-case basis.”