The Takaka Hill, which connects Golden Bay to Riwaka, has been left with "significant damage" after 16 slips were caused as ex-cyclone Gita tore through the Tasman District yesterday.
"We understand how important this highway is to Golden Bay and will be doing our best to get that link re-established," said Frank Porter, NZTA Transport Agency System manager.
"There are 16 slips between Riwaka Valley and the Summit of Takaka Hill with two sections of road completely washed away."
They estimate it will take several days before the road will be open again, and then it will still only be open to a single lane.
The New Zealand Defence Force have sent a helicopter to help people stranded in Golden Bay.
"It will also transport police to Takaka after slips cut access to these areas and conduct an aerial survey," it tweeted.