Copyright David Tenenbaum.
Copyright David Tenenbaum.
In many major American rivers, the U.S. Army Corps of Engineers has built a wide range of navigation and flood-control structures:
Throughout the 20th century, the Corps built and maintained an extensive system of locks, dams and levees on the Mississippi and Missouri Rivers, which drain most of the United States, east of the Rockies.
To farmers, barge companies and real estate interests, levees are critical for taming the rivers. But to environmentalists, they are artificial restraints that promote reckless development and farming in the floodplain. Certainly, some major rivers have been sundered from their floodplains. The Lower Missouri River, for example, occupies only about 10 percent of the floodplain, says Galat (see "Flooding to Restore... " in the bibliography).
And while levees do protect farms and towns during minor floods, the flood of 1993 demonstrated that giant floods will still reclaim the floodplain, no matter how high the levees.
The logical move, says Galat, is to get out of the line of fire -- to move away from rivers that refuse to be tamed. That's been done, to some extent: After the 1993 flood, several towns were relocated above the Mississippi and Missouri River floodplains.
But Galat observes that development is continuing in the floodplain. "There was a lot of fanfare about moving towns, but in the big scale, it was just fanfare. There's been little fundamental change in floodplain management." Malls and homes are being built smack in the floodplain, he observes, behind restored levees. Eventually, these levees will break again, he predicts, if the water does not simply rise above them.
Galat is one of many river scientists who favor putting the floodplain back to work as natural damper on flood heights and source of wildlife habitat. Since the 1993 flood, he says, 50,000 acres of floodplain in Missouri alone have been returned to the floodplain by opening levees in areas like the Big National Muddy Fish and Wildlife Refuge.
Like wetlands and forests, there are limits to how much levee removal can help. No matter how much he favors returning the floodplain, Galat insists this would not affect gigantic floods like the '93 on the Mississippi-Missouri system -- so many levees broke that the rivers occupied essentially their entire historical floodplains -- and still produced a whopper of a flood. In other words, even if some levees were removed, the river would likely run over the remainder during epic floods.
Rather than worrying about floods like the 1993 edition, which only come every 100 years or so, Galat says it's more sensible to examine what the effects of "messing with the river" are on the floods that occur every couple of years or so. The height of these floods, he says, is profoundly increased by building levees, wetland loss, deforestation, stream channelization and changes in land use in the watershed.
Water's rising! Check out our flood bibliography before it gets too wet...
There are 1 2 3 4 5 pages in this feature.
Bibliography | Credits | Feedback | Search