It will take weeks to regain access to some areas cut off by slips caused by weekend floodings, and some isolated communities will need emergency food deliveries, a Whanganui farming representative says.
Federated Farmers, local councils and rural support trusts are all working together to identify the areas of greatest need and organise relief.
An estimated 150,000 hectares of land has been damaged by slips or flooding in the Taranaki, and Manawatu-Whanganui regions.
Federated Farmers Whanganui president Brian Doughty said the Government's declaration of a medium scale adverse event was appreciated for the extra support measures it would deliver.
However, some areas would need a lot more help than that, he said.
"I suppose we're talking about the flats of the Whangaehu where the dairy farms are."
"We're talking about selected or specific areas of massive erosion in hill country on those north facing hills, where the sides of the hills have gone and the tracks and fences have gone, and that creates problem for stock control, for feeding and animal health issues as well."
Helicopters were today inspecting back country areas and delivering supplies.
"We're working with our district council, civil defence and emergency management and they've got helicopters flying in delivering food packages, for example the Whanganui River Road will be shut for another three to four weeks, so there will be food packages going up there all the time," Mr Doughty said.
"Yesterday we flew over and it's absolutely munted, there are some massive drop outs ... the road has completely gone and that's going to take some considerable time to fix.
"We think for the farmers that are up there, there will be food deliveries, there will be medical supplies and these will all be pretty much flown in on a daily basis."
Mr Doughty said as well as food for people, stock feed was a pressing need and farmers needing feed or offering it and other help should contact Federated Farmers on 0800 327 646 or the Rural Support Trust on 0800 787-254.