Floods are the most destructive, most frequent and most costly natural disasters on earth. And they're getting worse.
Floods have caused hundreds of deaths and billions of dollars of damage around the world this summer. The worst floods in 50 years killed at least a dozen people in Texas and destroyed 1,000 homes, and other states have also been hit hard.
England has suffered unprecedented rainstorms and serious floods; cleanup is expected to cost insurance companies $3 billion. Several hundred have been killed and hundreds of thousands evacuated in Bangladesh, China, India and Pakistan. Australia, Japan and Switzerland have been hammered.
Flood damage is soaring partly because global warming is leading to more intense storms, and partly because more people are living and working on flood plains. Flood-control measures, which are supposed to protect us, are in fact a key part of the problem - and the limitations of conventional flood control will become ever more evident as global warming-induced super-storms test dams and levees beyond their intended limits.
The time has come to recognize that all anti-flood infrastructure can fail. This must be accounted for in flood planning.
When New Orleans was devastated in 2005, the primary cause was the failure of the city's poorly conceived and maintained flood defenses. The Army Corps of Engineers' levees were supposed to be able to protect New Orleans from a Category 3 storm. But according to the National Hurricane Center, Katrina was at most a Category 2 when it hit the Crescent City.
New Orleans suffered the consequences of a failed "hard path" flood control system that ignored the complex workings of the Mississippi River and delta and the nearby coast. Flood damage soars when engineering projects reduce the capacity of river channels, block natural drainage, increase the speed of floods and cause the subsidence of deltas and coastal erosion.
"Hard path" flood control based on dams and levees can also ruin the ecological health of rivers and estuaries. Dams and levees can never be fail-proof. When they fail, they do so spectacularly and sometimes catastrophically. They also provide a false sense of security that encourages development on vulnerable flood plains.
As many as 230,000 people died when a chain of dams failed in central China in 1975. The Kaloko dam in Hawaii breached last year, killing seven. Also in 2006, sudden releases from a dam killed 120 people in the Indian city of Surat.
There is a better way to deal with floods: the "soft path" of flood risk management. Instead of spending billions of dollars vainly trying to eradicate floods completely, we can save money and lives by recognizing that floods will happen and learning to live with them as best we can. This strategy is also based on an understanding that some flooding is essential for the health of riverine ecosystems.
A "soft path" approach means taking measures to reduce the speed, size and duration of floods by restoring meanders and wetlands, as in Florida's Kissimmee River restoration project. It means protecting our most valuable assets by raising isolated houses on mounds or stilts and defending built-up areas behind carefully planned and well-maintained levees.
It also means doing all we can to get out of floods' destructive path with improved warning and evacuation measures.
Such practices are already in use in some parts of the United States and around the world. After the disastrous 1993 Mississippi floods, some 10,000 homes and businesses were relocated from the flood plain. In Northern California, a 10-year, $220 million project to reduce floods on the Napa River will restore tidal marshlands, remove some buildings in the flood zone and set back levees.
Despite a growing consensus that mitigation, not elimination, is the only realistic flood policy, there remains a powerful faction devoted to outmoded, "hard" flood control. Among these diehards are many (although not all) engineers at the Army Corps of Engineers, and the developers and local politicians pushing to build subdivisions below sea level in California's Sacramento-San Joaquin Delta.
Improving our ability to cope with floods requires adopting a more sophisticated set of techniques. The "soft path" of flood management should be a core part of efforts to adapt to a changing climate. Such a strategy will not only reduce deaths and damage but also save money and bring us healthy rivers and wetlands.
Patrick McCully is executive director of the International Rivers Network. His e-mail is patrick@irn.org.