Atacama Desert, Chile, 2003

National Geographic picture of the day.

A vizcacha, close relative of the chinchilla, rests on an outcropping in Chile's Atacama Desert.

Why is Africa flooded?

FACTBOX - Deadly Floods Hit Africa's Usually Arid Sahel

AFRICA: August 16, 2007

Heavy seasonal rains have caused deadly and destructive flooding across Africa's Sahel region, a vast swathe of land on the southern edge of the Sahara which is dry for much of the year.

Following are details of some countries affected.

SUDAN - More than 70 people drowned in several states in the worst flooding for a generation after weeks of heavy rain in Africa's biggest country. Flood waters have spread diseases such as cholera, which has killed at least 53 people this rainy season. More than 30,000 homes have been destroyed and at least 40,000 more damaged. Some 365,000 people have lost all or part of their home, household goods or food stocks.

KENYA - Up to 20 people feared killed beneath mudslides which destroyed homes and injured 39 people last weekend in west of country, where such mudslips are rare.

NIGERIA - At least 14 people killed and some 7,000 forced from their homes in the central Plateau State since Sunday. Heavy rains caused damage and forced thousands more families from their homes in other areas, including sub-Saharan Africa's most populated city, Lagos.

CHAD - At least three people killed in southwest Chad after heavy rains last weekend of up to 5.7 inches in some areas. They destroyed more than 700 houses and damaged 5,000 more homes in the administrative areas of Torrock and Tikem. Thousands of livestock killed.

MALI - Heavy rains since July, including downpours of up to 9 inches in some places have killed at least four people, including three children swept away by floods in San. Rains damaged hundreds of homes and cut off major roads between the capital Bamako, on the banks of the Niger river, and provincial towns.

NIGER - 20,000 people left homeless by rain and flood damage since July.

BURKINA FASO - 6,000 people affected by floods in Bama area after 6.5 inches of rain fell on the night of July 28. Government appeals for 1,500 tents to house 4,000 homeless.

IVORY COAST - Heavy rains and floods in late July forced more than 1,000 people from their homes in southern town of Agboville. Some 2,000 people still struggling to find safe drinking water after floods contaminated wells with sewage.

SENEGAL - Heavy rains a fortnight ago and at the weekend damaged and destroyed houses in the town of Thies, where 5 inches of rain fell on Sunday night and Monday morning, forcing some businesses including banks and pharmacies to close for two days.

Sources: International Federation of Red Cross & Red Crescent Societies/local Red Cross; United Nations Office for the Coordination of Humanitarian Affairs; Malian Territorial Administration Ministry; Reuters; IRIN news; local media. REUTERS NEWS SERVICE

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Aid to Help Asia and Africa With Effects of Warming

The Rockefeller Foundation says it will invest $70 million to help Asian cities and African farmers withstand floods, droughts and other global warming hazards.