Flood-fighting changes are needed

By Des Moines Register

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Iowans whose fields, yards and gardens are bone dry might have been surprised by flooding along the lower Mississippi River this spring. It's a reminder of the enormous size of the Mississippi watershed that covers 31 states stretching from Canada to the Gulf of Mexico and from the Rockies to Pennsylvania. Spring snowmelt and rains anywhere in that basin can push the Mississippi out of its banks.

This year's flood got unusual attention when the U.S. Army Corps of Engineers dynamited a levee in Missouri, flooding tens of thousands of acres of farmland, and then opened the gates on the Bonnet Carré Spillway in Louisiana, which will provide a direct route for floodwaters to Lake Pontchartrain, flooding recreational areas in the process. Both actions relieve pressure on flood-control structures and protect lives and communities downstream.

These moves by the Corps are not just because of the magnitude of this flooding, but a reflection of a shift in policy by the Corps in how it fights floods. A better word might be “manage,” because consensus is growing that there is a limit to how much vertical infrastructure - flood walls and earthen levees - can be built to protect land and buildings from floodwaters.

Higher levees move the water faster and intensify the problem downstream. At some point, nature must be allowed to take its course, allowing water to spread across bottomlands, slowing the cascade of water, easing the stress downstream on levees.

Some environmental groups have long argued for minimizing floods by holding more water upstream through better land use, protection of wetlands and creation of easements for water storage during flood seasons. The Corps of Engineers is in the process of revising its policies to put this philosophy into practice.

It could not come at a better time.

Iowa and other Midwestern states are seeing more frequent flooding within all river basins, including those that feed the Mississippi, and they likely will see more. The anecdotal evidence is obvious after successive years of 100-year and 500-year flood events in just the past two decades. A report to the governor and Legislature in January by a team of scientists and experts at the three state universities documented extreme precipitation in the past 40 years and predicted the trends will continue “well into the future.” ...

Along with changing flood management strategies, states in the Mississippi River basin must adopt new land-use policies: They must discourage intensive development in flood-prone areas, expand and preserve wetlands and set aside land for temporary water storage. In Iowa, this will require fundamental changes in thinking, changes in state law and changes in local land-use regulations.

There was considerable agreement on the need for these changes following the historic floods in 2008, but resolve has waned. Perhaps the images of flooding on the Lower Mississippi this year will serve as a reminder that it will happen again here.