The provincial government in Oro in Papua New Guinea says about 10,000 traditional houses have been destroyed by days of torrential rain brought by Cyclone Guba.
The acting provincial administrator, Paul Namino, says the confirmed death toll of people swept away by the floodwaters is 71 but he thinks the final figure may exceed one hundred.
Mr Namino says the flood waters in much of the province are waist deep while the rain is still falling.
He says tens of thousands of people are trying to shelter on higher ground and there is a struggle to get them the most basic of supplies.
"Water is a problem and the basic supplies - food, in many cases water containers, tarpaulin for temporary shelter - that is very basic at the moment, and of course clothing for those people whose homes have been washed away, and cookeries [ utensils ]."
The acting provincial administrator in Oro Province in PNG, Paul Namino.
He says they have one helicopter available to deliver supplies but just one pilot so the aircraft is sitting idle for long periods each day.