Authorities say a detour will be in place by this afternoon.
The 20m section of the trail was reported as slumping on Friday after high river levels scoured into the bank, Queenstown Lakes District Council community services general manager Paul Wilson said.
"Over the weekend it became apparent the area was slumping further and we have had to take action to close the trail at that point for safety reasons," Mr Wilson said.
Repairs would take 2-3 months but the detour would keep the trail open, he said.