The Moutua floodgates between Foxton and Shannon have been opened this morning by the Horizons Regional Council amid heavy rain caused by a polar vortex.
The Moutua floodgates between Foxton and Shannon have been opened this morning by the Horizons Regional Council amid heavy rain caused by a polar vortex.
The Moutoa floodgates between Foxton and Shannon were opened this morning to relieve pressure on the bottom stem of the Manawatū River.
Horizons Regional Council incident controller Sarah Carswell said the floodgates, which were opened at 4.15am, divert water down a spillway which acts as a shortcut to the sea.
“The bottom stem of the Manawatū River is windy and has a relatively shallow gradient, slowing water down. As this happens, the channel fills, and risks significantly overtopping a 30-kilometre stretch and flooding adjacent properties,” she said.
“There’s a common misconception that opening the gates acts like a plug, draining upstream and dropping levels in the likes of Palmerston North and the Tararua District.
“Diverting flood flows down the spillway reduces this downstream risk. However, this diversion has no impact on water levels upstream.
“We also can’t operate the gates until the river is within the operating range of 8.2 metres at Moutoa as there needs to be enough flow left to not deposit heaps of silt into the lower channel.”
Carswell said people who lease land along the Moutoa spillway were advised on Sunday afternoon the gates could be opened.
The Manawatū River is close to the level that would see the floodgates at Moutoa open.
“We appreciate the response these leaseholders take during flood events to move stock and drop fences, sometimes at short notice, before we operate the gates,” she said.
The worst of the rain appears to have passed over the region, but river and stream levels will remain high for some time and Horizons staff are continuing to monitor catchments.
“People should continue to stay away from low-lying areas and avoid entering flood waters. It should always be assumed flood water is contaminated. Anyone who has flooding on their property should contact their local city/district council.
“Flooded streams and rivers are also dangerous. Currents will be strong and debris such as logs will often be difficult to see.”
Road conditions will vary across the region, with State Highway 56 at Ōpiki shut due to flooding, she said.
“People should also aim to avoid the Pahīatua Track, which suffered slips and fallen trees on Sunday. While it may be open now, other routes – such as the Saddle Rd – may be a more reliable option,” she said.
“There is also snow forecast to fall to about 1000 metres in the Desert Road area throughout Monday. It only takes a couple of centimetres of snow on a road to make driving dangerous, so people should avoid travel where possible until conditions improve.”
Updated information on river heights and rainfall is available via Horizons’ 24-hour toll-free Waterline 0508 4 FLOOD (0508 435 663), or online.
