Visibly exhausted, Ali Fonj sets to chopping wooden poles to make a shelter for his wife and four children after their ramshackle home was swept away in raging floodwaters in South Sudan. Fonj, 45, is one of around 150,000 refugees from Sudans troubled Blue Nile region who had fled to Maban, in neighboring northeastern South Sudan. Their precarious lives have now received a second blow -- the regions worst floods in a generation. Fierce rains across East Africa have had deadly consequences in Somalia, Kenya, Tanzania and Ethiopia. The UN refugee agency UNHCR says nearly a million people have been affected in South Sudan. In Maban, the floodwaters are slowly receding but submerged homes and damaged crops bear testament to the devastation. "When the water came, I took all my children and sought refuge at a nearby school," a dejected Fonj told AFP. The family were told to leave when classes resumed. "We are trying to build shelters and we can cover them using the plastic sheets distributed to us by the UNHCR until the water dries up, so we can then be able to go out and get some thatch to build a better shelter for our children to stay in."Worst floods in decades Fonj lives in one of four refugee camps in Maban, housing people who fled violence in the Blue Nile region where fighters continued their campaign against Khartoum after being excluded from an independent South Sudan in 2011. A host community of around 50,000 people in Maban have also been badly hit by the floods, which the UNHCR says has left six dead locally. "They have never seen this magnitude of floods since 1984," a senior UNHCR official in Maban, Malar Maharajah Smith, told AFP. The refugee agency estimates that across the country, which was already facing one of the worlds worst humanitarian crises due to over five years of war, some 600,000 people are in need of immediate assistance. Floodwaters also destroyed latrines and contaminated sources of drinking water, raising fears of waterborne diseases. According to the UN, some $61 million (55 million euros) is needed to respond to the aftermath.No firewood Another camp resident, Mukbulah Saleh, 25, clasps her shoes in one hand and a saucepan containing food items in another as she wades through floodwaters. "We have nothing to use to cook the little food I got because it is still not safe for us to go to the bush to collect firewood since there is still water all over," she said. Some flood victims are waking up at dawn, armed with mosquito nets, spears and sticks, to try and catch the unexpected bounty of fish that have shown up in floodwaters. "This flood came to kill us but God was in our favor, it brought for us fish instead," said Mabanese resident Abdul Gasim Dafala, holding up his catch.