Queenstown Lakes District Council (QLDC) will hold an extraordinary meeting on Monday to consider reports on flood mitigation measures at the Shotover Delta.
"All we're looking for from Monday's meeting is authority for me to speak to the regional council about funding the Shotover Delta Training Works," QLDC chief executive Duncan Field said.
The Otago Regional Council (ORC) was preparing to apply to itself and QLDC for a suite of resource consents to substantially lower the bed of the delta by gravel extraction and construct an estimated $1.2 million training line across the bed to encourage the river to flow on the left hand side, instead of the usual right hand side, and join "in a positive manner" with the Kawarau River.
QLDC, ORC, Queenstown Airport Corporation Ltd and the New Zealand Transport Authority formed the Shotover Delta Steering Group to take a holistic approach to a series of landscape-changing multimillion-dollar projects.
These projects are Shotover River management, the construction of the airport's runway safety extension, the disposal of wastewater, a land scheme called Project Shotover, a public recreational greenbelt reserve, and a possible Frankton Bypass through the delta in 35 years.
"The good news is we've managed to accommodate all those projects and end up with a very attractive entrance to the town at the same time," Mr Field said.
Parts of the resort's central business district were inundated by floodwater in 1994-95 and in 1999 and the river management works the group were proposing aimed to mitigate future damage, he said.
"What the regional council has identified is the Shotover River has a big impact on how quickly Lake Wakatipu drains. What happens when the Shotover floods, it stops the lake from emptying water and you can get backflow into the lake from the Kawarau River.
"That effect is minimised if the Shotover River stays to its true left bank but the river tends to want to come to the right. So these works are designed to keep the river in the correct place.
"If it comes to the right hand side it will prolong the flood event. If you had a similar rain event to 1999, you would have the same high lake level, but if the river runs to the right hand side the water won't be higher and in town for longer."
Mr Field said the Shotover had filled up with gravel and three islands of willows.
The works would make the Shotover a braided river once again, which meant it would scour itself out and take the gravel it accumulated downstream.
ORC chief executive Graeme Martin said forming the training line and lowering the delta bed had been developed out of physical and mathematical models and research over the past six years.
The measures could not guarantee a flood would not occur but guaranteed the flooding would not be worse than in 1999.
The alignment, length and form of the training line were being finalised.
However, Mr Martin said it was likely to be about 1km in length and run from the edge of the bottom of the sewage ponds and parallel to escarpment for two-thirds, then curve out across the delta bed.
Specialist river control willows and shrubs would be planted beside the line and grow to give protection and blend in with the terrace landscape.
Mr Martin said construction would cost a pre-feasibility estimate of $1.2 million, which would be funded by Otago Regional Council ratepayers, subject to public consultation.
Mr Field said a lot of the gravel would be used to form QAC's proposed runway end safety area, which would be a 90m long and 45m high embankment for undershooting or overshooting aircraft, as required by Civil Aviation by 2011.
The approximate million cubic metres of gravel for Shotover management would be used on two of the steering group's projects - up to 650,000 cubic metres on the runway end safety area over the next three years and 350,000 cubic metres on the wastewater treatment scheme over a 13-year period.
Mr Field said when gravel extraction took place depended on the resource consents process, but February 2009 was likely if there was no Environment Court appeal.
Otago Regional Council and QAC were working out how the gravel would be removed, he said.
The runway end safety area proposal was being reviewed by planning commissioners and the consents for Project Shotover were notified last month.
