Man vs. Nature: Why Floods Still Win
New Orleans has only gradually resurrected itself after the city drowned five years ago this week following Hurricane Katrina. That process echoes an unpleasantly familiar drama that has played out countless times around the world during human history.
Building on the coasts and near the fertile floodplains of a river has allowed settlements access to water for trade and agriculture since the earliest days of Egypt and Mesopotamia, according to Greg Aldrete, a historian at the University of Wisconsin in Green Bay. That choice has often come back to haunt people when the floodwaters rose.
"That tension has existed since the very dawn of civilization," Aldrete told LiveScience. "People tend to build cities in floodplains." [Graphic:What Happened in New Orleans]
Disaster has frequently followed, even if none has quite rivaled the biblical flood which set Noah's ark afloat. The Mississippi River broke through the levees and displaced hundreds of thousands of Americans in seven states in 1927. China has historically suffered great loss of life through floods, including the 1931 flooding of the Yellow River that may have killed millions
Humans have tried to control the waters with levees and dams, essentially rerouting Mother Nature using a complex network of barriers. But the most massive engineering projects can often lead to even more complex problems, experts say – especially if planners fail to prepare for the worst. And then there's the expense, as some vulnerable towns and cities just can't afford a massive engineering project to keep out floodwaters in some future storm.
Leaking levees
Levees did not save New Orleans during the extreme events of 2005, when Hurricane Katrina only sideswiped the city rather than striking it directly. Now the U.S. Army Corps of Engineers labors to build an extensive system of defenses to replace what had been "a system in name only," according to its report on the Katrina catastrophe.
Other concerns exist for the 1,600 miles (2,574 kilometers) of earthen levees protecting the city of Sacramento, Calif., a sprawling inland community with extensive suburbs all situated at the confluence of the Sacramento and American rivers. The aged system requires both repairs and upgrades to get it up to current design standards, said Tom Brandon, a civil and environmental engineer at Virginia Tech.
Scientific reports have characterized Sacramento, the state’s capital, as a disaster waiting to happen next time a major flood strikes.
"The consequences of failure there are great – perhaps billions of dollars of damage," Brandon said.
Those considerations come at a time when many regions around the world have been stricken by floods. Surging waters have stranded or displaced millions of people in hard-hit Pakistan, China and Niger during August alone.
When the levees don't exist
This month has spelled bad news for many U.S. communities as well. For instance, the 56,000-person town of Ames, Iowa endured record flood levels as water overflowed from Squaw Creek and the South Skunk River in early August.
Both waterways eventually lead to the Mississippi River, where an extensive system of privately owned levees keeps the floodwaters contained — at least some of the time. But Ames has no protective levees besides natural sediment buildup or raised roads, said William Simpkins, a hydrogeologist at Iowa State University.
As a result, many Ames buildings on the local floodplain were underwater. Some businesses such as Happy Joe's Pizza have given up after the recent flood damage, Simpkins said. The pizza parlor had built a small wall to protect itself against the 1993 flood levels, but to no avail.
The local Wal-Mart and Target both survived because they had raised their ground levels above the "100-year floodplain," but that presents too expensive a solution for most of the town.
Of course, nobody even knows if the latest flooding represents a 100-year event or a 500-year event, Simpkins said. The term 100-year flood itself can also become misleading.
"I think people are under the illusion that if there's a 100-year flood one year, you're not going to have one the next year," Simpkins told LiveScience. "But in 2008 there was a large flood, and the one a few weeks ago was even bigger."
Levees or even a dam might help control future flooding. But Simpkins said that taxpayers may balk at the expense, and pointed out that existing dams face criticisms about how well they manage water levels.
"Better planning on the floodplain and incentives for businesses to move to high ground might be cheaper in the long run than building a multimillion-dollar dam," Simpkins said
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