Waharau Bridge on East Coast Rd north of Kaiaua will be closed to all traffic from around 2.30pm as Hauraki District Council engineers attempt to carry out essential work on the fast-eroding bridge.
The bridge has been open to essential services and residents this morning, but the rising floodwaters are causing erosion of the bridge abutments, the council said, making it "increasingly unsafe for vehicular traffic".
A large slip on East Coast Rd has blocked access from the north of the seaside village, so the community will be completely cut off for vehicular access on both sides once the bridge closes, the council said.
"Hauraki Civil Defence has sent teams to assess the situation and offer assistance to residents."
Those wishing to evacuate the settlement are advised to do so before 2.30pm.
"At this stage it's unknown how long the area will be inaccessible to vehicles but residents can stay updated via Hauraki District Council's website and Facebook page."