The NZ Transport Agency is advising drivers there is a risk that higher than normal tides in the Waitemata Harbour could flood some sections of the Auckland Motorway network tonight and tomorrow (Wednesday 6 June).
Areas at most risk are the Northwestern Motorway (State Highway 16) causeway across the harbour, and the Northern Motorway (SH1) southbound lanes from the Esmonde Road interchange at Takapuna to the Exmouth Road footbridge. Critical times will be tonight's high tide at eight o'clock, and again tomorrow around 8am and at 9pm.
"There is a high risk of flooding when the tides peak," says the NZTA's State Highways Manager for Auckland and Northland, Tommy Parker. "We're on flood alert and have a number of measures in place to ensure the motorways at those points remain safe, but people will need to take extreme care over the next day or so."
Motorway conditions are being monitored from the Joint Traffic Operations Centre at Smales farm. Roadside variable message boards will keep drivers informed. Response crews from the NZTA's Auckland Motorways Alliance are on standby to close motorway lanes if necessary and redirect traffic.
Average "normal" high tides in the Waitemata Harbour vary between 2.6 and 3 metres, but it is expected high tides over the next two days to vary between 3.4 and 3.6 metres. The high tides coincide with a rain front accompanied by strong winds moving across the country. The front's low atmospheric pressure can increase tide levels in the harbour.
"It's almost certain the Northwestern cycleway adjacent to the motorway will be flooded - we are asking people to avoid using it 90 minutes either side of the high tides," Mr Parker says. "Tidal water could also cover bus lanes or outer traffic lanes on the motorways. We'll do everything we can to keep the motorways fully open and safe but the weather - particularly the wind - will be the critical factor over the next 36 hours."