Flood of evidence

Furious floods

Too many floods

Fewer trees = more floods?

Wetlands and floods

Flood prevention: the earthmover approach


Many rivers are designed to flood. Can we -- should we -- prevent floods?


In constant dollars, 1998's "natural disasters" cost more than all of nature's diasters in the 1980s. Should we blame habitat destruction, global warming, increased population, or all three?

Data courtesy Munich Reinsurance and Worldwatch


Statue of man reading a book on a park bench sits half-submerged in flood waters On Riverside Drive in Covington, flood waters surround this statue of a man reading a book on a park bench (Patrick Reddy photo).

Courtesy The Cincinnati Enquirer.

Floods: Fount of misery
With building material balanced on her head, a woman carries her baby through a flood. Guarding the essentials during the recent flood in Mozambique. Courtesy Associated Press
16 Mar 2000 After weeks of rain and storms in February, Mozambique's rivers were covering floodplains by the thousands of square kilometers. As people desperately sought higher ground, they were chased out when the waters rose further. With their wells under water, the flood refugees drank polluted water, raising the specter of epidemic.

As international agencies and militaries gradually move into position, the death toll is unknown, but probably is in the thousands.

The natural disaster capped a year of rapid economic growth after decades of civil war, destroying homes and businesses, killing livestock, and apparently setting the economy back by several decades.

But was the flood really a natural disaster, or did human actions contribute to it? What, for example, was the effect of removing 99 percent of the trees in the watershed of the Limpopo River in Mozambique over the past 50 years? The Limpopo was the major source of the floods.

Tree leaves cushion raindrops, allowing more water to enter the soil. Tree roots both stabilize the soil and dry it out. But when uplands are stripped of trees, rainwater, instead of being absorbed, is immediately released to the streams and rivers. The result, observes Janet Abramovitz of the environmental group Worldwatch, is that rains that might have caused small problems now cause floods.

A bar chart showing losses below $20 billion per year during the 1980s, and more than $80 billion in 1998.
Overall, "natural" disasters have taken on a new urgency. In constant dollars, the toll in 1998 alone exceeded the economic toll of the entire decade of the 1980s. Floods are probably the most destructive type of natural disaster. We see a flood of evidence that inundations reflect human action rather than simply rainfall amounts.

  • Growing populations put more people in harm's way.

  • Coastal development is exposing more people to the wrath of hurricanes.

  • Beaches are eroding as the sea level rises.

  • Deforestation removes trees that slow runoff into rivers.

  • Wetland destruction eliminates natural sponges that absorb runoff.

  • Levees, dams and other river control structures intended to reduce flooding can, ironically, make floods more destructive.
The links above go to Why Files coverage of some flood-related issues. Is there a human hand behind the rash of floods?

The Why Files

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