Storm water runoff concerns continue to grow

Storm water runoff crosses reserve and track before spilling into Clutha River. | Photo: Wanaka Sun

Queenstown Lakes District Council (QLDC) is assuring the community that it is addressing the increasing concerns surrounding the Hikuwai and Northlake development management provisions and the effect they appear to be having on increased flows of discoloured water into the Clutha Mata-Au River during rain events.

QLDC communications advisor Lu Morris said the council is working alongside Otago Regional Council (ORC) and focusing on the overall design and management of the on-site storm water systems, which require appropriate protections installed in order to remove potential contaminants from the storm water. Morris said that, despite the improvements made to the site management of the water run-off, QLDC enforcement officers are urgently looking to address improvements to these provisions.

Developers are required to meet specific on-site management plans in order to meet sediment discharge and flow limits. This involves adhering to the conditions of the Regional Plan: Water for Otago, which mandates that on-site drainage does not cause a conspicuous change in the colour or visual clarity of the receiving water.

“We are currently looking at further actions that need to be taken across the developments and for the individual building sites. As soon as we have an agreed plan in place, we will provide what details we can. No time frame is currently confirmed for this, but we would hope to provide an update within the next two weeks,” said Morris.

Otago Fish & Game officer Paul van Klink compared pre- and post-development runoff and said rainfall levels remain the same, yet earthworks and poor on-site management have increased the runoff as it travels through a single outlet through the Hikuwai Reserve rather than it naturally seeping into the ground and dissipating into a wider area free of sediment.

“The issue here is that the subdivision earthworks have modified the landscape, scraped off the top soil over large areas of land and left it bare. Rainfall has collected sediment from the exposed surfaces which is carried into storm water which has been channelled it into a single discharge point through Hikuwai and into the Clutha River. So what you’re seeing is an increase in overland flows, so an increase in quantity and an increase in sediment laden water. The water leaving the site is caused from a really poorly managed subdivision development.”

Department of Conservation (DOC) senior community ranger Annette Grieve echoes the concerns raised by the community. “The storm water discharge from the subdivisions continue to cause track damage and sediment build up within the conservation area. DOC is consulting with ORC and QLDC on these matters.”

Otago Fish & Game is also supporting QLDC and ORC as both councils work towards a solution.  

Hikuwai and Northlake development management teams did not respond to requests for comment by the time the Wanaka Sun went to print.

Read: Stormwater infrastructure under investigation



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