The first of about 120 trampers have been evacuated from parts of Fiordland, which had been flooded by the weekend rain.
Department of Conservation programme manager Ross Kerr said 120 trampers on the Milford Track had been holed up in three huts for the past two nights, but diminishing food supplies meant evacuations were necessary.
Rainfall measuring 793mm had doused the Fiordland National Park and Southland district since Saturday night and there was no sign of it letting up.
The trampers were being flown out of the area and being delivered to the head of Lake Te Anau, where boats would ferry them to the town.
"We'd expect the first boatload back to Te Anau probably sometime after 3pm,'' Mr Kerr said.
The last two tramping parties for the season had been cancelled, he said.
Another 50mm of rain was expected this afternoon and another 60mm due tomorrow.
Flooding has caused extensive damage to fences and other infrastructure on farms in the Te Anau Basin, while river levels continue to rise across Southland, Environment Southland said.
The Oreti River may reach the same levels as in November 1999, which caused widespread flooding of farms and roads. The river was expected to be contained within the stopbanking system but areas which were flooded in 1999 could expect to be flooded again.
The flooding has prompted the Southland Civil Defence Emergency Management Group to advise motorists to avoid non-essential travel.
Environment Southland's hydrologists were monitoring the rivers and modelling the impact that further predicted heavy rain would have on already high water levels.
The Hamiton Burn, a tributary of the Aparima River, had already exceeded its highest recorded level, duty floodwarning officer Karl Erikson said. However, there were no concerns for the community of Otautau at this stage.
