By Barry Malone

ADDIS ABABA (Reuters) - More than a quarter of a million Ethiopians are risk from severe flooding next month when heavy rain is expected in the country, according to government estimates issued by the United Nations on Monday.

The U.N. Office for the Coordination of Humanitarian Affairs (OCHA) said 19 people were killed in mudslides after flooding last week and nearly 12,000 people had been displaced since then.

"Some 270,000 people could be affected by flooding in the (Amhara region)," OCHA said in a statement, quoting a contingency plan issued by regional authorities.

Flooding often affects Ethiopia's lowlands during the rainy season between June and September. In 2006, more than 1,000 people were killed and more than 300,000 made homeless.

"New flooding has been reported in recent days, including in the eastern Amhara lowlands and in northern Somali Region," it said.

The plan says $6.8 million would be needed to respond to such an emergency.

The country's disaster management office gave a lower estimate, saying 153,000 people were likely to be affected by next month's floods, of whom 25 per cent could lose their homes.

"Good contingency planning needs to be in place," an aid worker monitoring the flooding told Reuters. "According to data from the meteorological office, the heavy rains will continue through September."

Almost 5,000 people who fled to higher ground are now stranded and inaccessible to local authorities, according to the OCHA statement.

Significant flooding damages the country's agriculture-based economy, washing away thousands of cattle, ruining crops and submerging roads.

Reuters