Thursday, December 16, 2010

Fatal floods in Africa

Philip F. Schewe in Inside Science News Service: When natural disasters claim human lives, it's important to determine whether the problem is geophysical or cultural. A new study shows that the large upswing in flood deaths in Africa over past decades is chiefly the result of population settlement patterns, and is not a consequence of changing climate.

Floods displaced 2.5 million people in Africa in 2009 and more than a million in 2007. Overall African flood fatalities increased by a factor of ten from 1950 to 2009. Over 15,000 people died during the decade 2000-2009. The human population in areas prone to flood damage also increased by a factor of ten over the same period.

Why do people live in places that flood? Historically people are drawn to riverbanks and coastlines for a number of reasons: jobs, irrigation water and easy transport. Six scientists made a detailed study of the water discharge of African rivers over the years from 1900 to 2000 to see if the rivers themselves had changed, perhaps due to climate change. They found that the amount of water coursing through the rivers hasn't changed that much.

Despite a tenfold increase in flood deaths, the consistent river flow and the tenfold increase in the population settled in flood-risk areas suggested to the new study's authors that the problem is chiefly one of human settlement patterns…

The yellow-to-red areas on this map of Africa show population growth over the period 1960-2000. The location of floods over the period 1985 to 2009 are denoted by dots and deadly floods by black circles. Credit: Courtesy Giuliano Di Baldassarre

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