The World Bank and the Fiji government released the study at the COP23 climate change talks in Bonn which are presided by Fiji.
A lead economist with the World Bank Stephane Hallegatte said the Climate Vulnerability Assessment used new methods to assess risk and to develop adaptation plans.
He said the study detailed a plan to build climate change resilience for Fiji which has been costed.
"The total cost is about nine billion Fijian dollars, about five billion US dollars, and to give a sense it's about 100 percent of the GDP of the country but would need to be spent over ten years."
She said while it was a large amount, the study budgets for it through a combination of private sector and government investment, and international community support.
Photo: RNZI/Sally Round Rotting piles under a school in Daku Village, Fiji which suffers from seawater inundation