The disaster co-ordinator in the autonomous Papua New Guinea region of Bougainville says as many as 60,000 people have been affected by two months of heavy rain.
Much of south Bougainville is a flood zone at the same time the region is coping with the impacts of the Mt Bagana eruption.
As a result of both natural disasters the Autonomous Bougainville Government last week extended a state of emergency until mid-October.
Esther Usurup said teams are now carrying out an assessment before food supplies are flown in.
"The whole of south Bougainville from Torokina to Siwai, Bana and Buin specifically, have also been inundated and, as of the last 24 hours we have had a rapid needs assessment that has been deployed," she said
Usurup said meanwhile that the volcano, Mt Bagana, is continuing to erupt, after bursting to life for the first time in 11 years on July 7.
She said it still carries a level two advisory.
About 3,000 people remain in camps for people displaced by the eruption.
They are at Wakunai and Torokina, which are either side of the mountain.
At least 5000 more are known to be affected by the eruption.
Ash from the volcano has polluted their water sources, wrecked their food gardens and caused some traditional houses to collapse.
Usurup said once information from the field assessment is available they will look to helicopter material into Buin, from where it will be distributed to those in need.
Usurup said rations are being brought in from Rabaul by the PNG Defence Force.
"The most feasible way to deploy all of the rations to Siwai and Bana and areas, and parts of Torokina as well as within Buin, is by air. So we are collating the quotations now for the chopper service for us to try and ensure the deployment of the rations, or initial food ration supply to the flooded areas will be deployed," she said.
The disaster co-ordinator expressed her gratitude for the help received from Australia, the United States and New Zealand.
New Zealand's aid has included doctors and nurses sent to the displacement camps at Torokina and Wakunai as well as the disaster advisors who arrived this week.
"They will be assisting the operation as well as the strategic cell in developing needed planning, documentation on the job, as well as key lessons and on-the-job training for our emergency teams and also assisting me when it comes to the strategic level of how to address the disasters currently facing us," she said.
The disaster officials sent to Bougainville include two from New Zealand's National Emergency Management Agency (NEMA) and one from Foreign Affairs and Trade.
Usurup said it was a remarkable thing to see all three nations working together to help Bougainville.
"That in itself had a great feeling of collaboration, knowing full well that the last time these three alliance forces were here was back in 1942. So having all three come together and band around us at this time was greatly appreciated and with sentiments that will last a life time for what was done for us," she said.