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Public Radio's Environmental News Magazine (follow us on Google News)

River Engineering

Air Date: Week of

Host Steve Curwood talks with Kevin Coyle, president of American Rivers, about the ways in which human engineering and nature combined to worsen the impact of this summer's Midwest floods.


CURWOOD: As the worst flooding in a century continues along the Mississippi and its tributaries, we thought we'd take a look at how the ecology of the nation's biggest watershed is being affected. Since the last monster floods, millions of people have settled in the floodplain, and a system of levees, dams and navigation channels has substantially altered the natural run of the river. Kevin Coyle is president of American Rivers in Washington. While the flooding is disastrous for people, he says it's having a mixed effect on the river's ecology.

COYLE: One analysis is that the natural areas along the Mississippi River will actually be enhanced by the flooding because soils, sediment and so forth will be able to spread out over the natural floodplain, for the first time probably in many years, and that vegetation and wildlife and so forth in the long run will be enhanced, although in the short run much of this will be destroyed.

CURWOOD: What's been the danger from this flood? Is it agricultural chemicals, is it raw sewage, is it petroleum products, is it Superfund sites? What's the pollution danger from the flood?

COYLE: For the most part it's not agricultural chemicals, because these will be so diluted by the massive amounts of water flowing down the river that we really won't see that as a major factor. The short term problem with pollution is that a lot of raw sewage is going into the river as a result of the breakdown of sewage treatment plants. But that's a short-term problem. Ultimately the river itself will clean itself up. The longer term question, and the real unknown, has to do with all of the landfills, the dumps, the underground storage tanks and so forth that exist up and down the river, that are suddenly under water. Many of these areas will wash out, and what that can do is create what we call a witches' brew of chemicals. Not only will chemicals and hazardous material get into the river but it will combine and recombine once it gets into the river. We think that the sediment, the bathtub ring, if you will, that will exist up and down the river as the flood waters recede will need to be constantly checked, because it's likely that there will be pockets of toxicity up and down the river.

CURWOOD: Now we hear that the levees have made this flood worse. What else have people done to the Mississippi that altering the river's natural functions - I'm thinking of dredging, diking, straightening, destroying wetlands. What role have those actions played in this flood?

COYLE: Well, first and foremost there is the concern about the levees trying to hold the river in rather than to have the floodwaters spread out over the natural floodplain. And what the levees do is they hold the water in and that increases the level of flooding, the cresting levels; moreover it increases the velocity of the river moving downstream, and that can cause downstream flooding problems. The Mississippi, in addition to being a major river, is also a major artery for commerce and industry, and one of the engineering problems with the Mississippi is that this navigation system has never really been reconciled with the flood control mission of the levees. So the navigation system tries to hold the levees close to the river; the flood control mission would want to put the levees farther away from the river, and this has really never been resolved in public policy. In addition to that, the Mississippi River has a number of so-called 'meanders', and in order to cut time down that it would take a barge or a ship to move upriver the US Army Corps of Engineers will literally cut off these oxbows and cut off these meanders, and in the course of doing that, what that does is it increases the velocity of the water moving downstream, so that it literally moves with more fury and in the process can break down the levees and erode the stream banks and so forth. I guess the final part of the navigation system and its effects on the river has to do with the dams and locks. What that has done is change the hydrology of the river, the way that the water flows, so that as the mud and soil and sediment that traditionally moved all the way down from the headwaters of the river to the Gulf of Mexico, that's all been cut off by these dams. And to the extent that there's no sediment, no mud in the Mississippi River, or it's cut off by these dams, that causes the water to be more erosive, and that also can cause the levees and the river bank to break down.

CURWOOD: Is it possible to live near rivers and not pollute them or do we not belong as human beings living in the flood plain?

COYLE: I think it's unrealistic to think that we somehow can avoid living near or around rivers. I think basically that we need to better protect the communities, because the taxpayer ends up paying for these communities, because the levee system did not protect them. Now that's to be distinguished with the levee system protecting farm land and we basically think there that when a monster flood occurs, that farming areas and undeveloped areas along the river ought to be flooded in lieu of communities, and we also think that the farmers should be compensated for this. But if there has to be damage that it fan out over the natural floodplain and the river be reconnected with the natural floodplain. And then finally to, really to reexamine the whole system to figure out where it is that the river is pinched too tight by the levee system.

CURWOOD: Kevin Coyle is president of American Rivers. He spoke to us from his office in Washington.



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