Four straight years of flooding have impacted more than 2.6 million people across South Sudan, forcing many to turn to wild fruits and leaves for sustenance, the report said.
"Roads and bridges have been washed away, health facilities abandoned or destroyed, crops and pastures submerged under water, families destroyed and parents separated from their children," the commission's chairman Manase Lomole Waya said.
The floods also led to the deaths of 172 people caught by rising waters, the report said.
"The affected people and communities are mainly relying on support of relatives and friends, fishing, eating wild fruits and leaves, selling animals, as well as the limited humanitarian assistance supplied," it said.
The annual floods since 2019 - a recent phenomenon that many experts link to climate change - have turned 10 percent of the country's arable land to swamp at a time when two out of three South Sudanese do not have enough to eat.
Last November, the United Nations warned that around two-thirds of South Sudan's population of 11 million people were at risk of severe hunger, surpassing levels seen even during the conflict in 2013 and 2016.
Four out of five in South Sudan live in "absolute poverty", according to World Bank figures for 2018.
UN: Flooding Hits 25% in South Sudan
JUBA - Nearly a quarter of South Sudan's population has been affected by years of unprecedented flooding, according to a report Tuesday by the UN Development Program and the government's relief and rehabilitation commission.