The NZ Transport Agency advises Auckland drivers that exceptionally high tides are forecast for the Manukau and Waitemata Harbours later this week, and there is a risk some low lying sections of the city's motorway network may flood.
High tides of up to 3.6m – about 0.5 of a metre higher than normal - are expected between Tuesday, 27 September, and Sunday 2 October. They will be at their peak on Thursday and Friday morning when commuter traffic volumes will be high.
“There could be some flooding, but the tides don’t pose a significant risk to the safe operation of Auckland’s motorways”, says the NZTA’s State Highways Manager for Auckland and Northland, Tommy Parker.
The area most at risk is the section of the highway and adjoining cycleway on the Northwestern Motorway (State Highway 16) causeway between the Patiki Road Interchange and the Rosebank Road Bridges.
“When the tides peak the cycleway will definitely be underwater, and we are asking cyclists to try to avoid using it 1.5 hours either side of high tide,” says Mr Parker. “Drivers should also cross the causeway with more care, and if necessary we will divert them on to arterial roads so that they can continue their journeys safely.”
As part of its project to complete the Western Ring Route motorway alternative to SH1, the NZTA is planning to raise the causeway by 1.5 metres and increase its width to provide extra lanes.