Walls of water forced through floodgates at Mozambique's mighty Cahora Bassa dam are worsening floods that have killed dozens of people, swept away hundreds of homes and threaten hundreds of thousands of people, Prime Minister Luisa Diogo warned Friday.
Riverside dwellers who ignored warnings to move to higher ground are surviving by clinging to trees in northern Manica province, the daily Noticias newspaper reported, quoting a district administrator.
Diogo said only the rooftops of a few houses could be seen poking above the floodwaters of islands in the Zambezi River valley, which she flew over Wednesday to assess the situation.
State television broadcast video pictures of stranded victims being rescued by canoe.
The images are reminiscent of floods in 2000 and 2001 in which over 800 people died.
This year's floods, affecting a swath of southern Africa from Angola in the west to Mozambique in the east, are not expected to claim as many lives because of disaster-management services set up after the last catastrophe, and early warning systems.
Seventy-one people have drowned in Angola and 29 in Mozambique, and hundreds of thousands have been left homeless in those countries and in Zambia, officials reported. Roads have been submerged, bridges damaged and power lines brought down by torrential rains and flooding which also has aggravated a cholera outbreak.
The U.N. World Food Program on Friday said it would call for international help, estimating that 37,000 acres of crops have already been lost in Mozambique and that up to 285,000 people will need food aid.
"The outflow of the Cahora Bassa Dam is likely to worsen flooding in the Zambezi River basin to levels not seen since the catastrophic floods in Mozambique of 2000 and 2001," the program's southern Africa director, Amir Abdulla, said in a statement.
He urged the international community to act early to help contain the crisis.
Mozambique's disaster agency has set up an emergency operations center in Caia, on the lower Zambezi River, with military helicopters and civilian canoes rescuing trapped people.
Raging waters in the Zambezi River are expected to rise with a large flood wave traveling down from the Cahora Bassa hydroelectric dam in northwest Mozambique.
On Wednesday, authorities doubled the discharge from its floodgates to nearly 10,000 cubic meters a second, even amid fears of the danger to people along river banks, Diogo said.
She said the lower Zambezi Valley is threatened by swollen tributaries of the Zambezi as well as the walls of water descending from the Cahora Bassa.
There was concern that a major investment in the area, a sugar plantation and mill owned by the Mauritian Sena company could be destroyed if waters overcome dikes that workers have reinforced with more than 1,000 sandbags this week.