When A Wetland Must Go.

Last week we learned that according to Federal law, wetlands should be considered Waters Of The United States (WOTUS) and therefore protected by the Clean Water Act, all because of The War of 1812 (with subsequent legislation and court rulings). It is therefore a violation of Federal law to dredge or fill (i.e., destroy) a wetland.

“But Paul,” you say. “Surely there are exceptions to the protection. Sometimes…A Wetland Simply Must Go!” And it’s true. Sometimes land development (for housing, airports, factories, whatever) will include a site with a wetland, and it is impossible to complete that project while preserving the wetland. In particular, roads impact wetlands: a straight line drawn across a map will eventually intersect with a wetland. It will happen. And we need a legal “escape valve” to handle these situations.

DSC_0339My visit to Indian Slough Wildlife Area in Louisa County made me think of this aspect of wetland law, because the property includes a wetland mitigation site. Broadly speaking, “mitigation” refers to reducing the negative outcomes of an action (such as destroying wetlands). It can include various remedies, but the typical scenario goes like this: a project will destroy an existing wetland, so the developer asks for legal permission to (just this once!) get an exception to the law—obtain a permit. The agency in charge is the US Army Corps of Engineers, and in granting a permit they essentially require you to sign a contract. In exchange for the right to destroy a wetland, you agree to do something appropriate (say, building a new wetland to replace the one being destroyed) as “mitigation” for your environmental impact.


In most states, probably the highway department (DOT) destroys, and mitigates, more wetlands than anyone else—not too surprising, given all the highway work done every year. Here at Indian Slough, they’ve established a DOT mitigation site in the floodplain of the Iowa River. As of this writing, the Google Maps imagery of the site actually shows the mitigation in progress (complete with the earth-moving equipment). Clearly, this is recent work.


During my visit a few weeks ago, I found…no wetland. We’ve had a droughty summer in southern Iowa, so I expected dry conditions. But the vegetation appeared to be almost exclusively upland (meadow) species. I followed up my visit with a contact from the county, and learned that the site was not yet planted. (Oh. OK, then.) Honestly, summer of 2017 would have been a difficult time to establish wetland vegetation here, due to dry conditions.




Will 2018 be better? No way to know, of course. The long-term outlook for whatever species they plant (or, that find colonize the site naturally) will depend on hydrology. If the site gets wet often enough, for long enough periods, it will develop wetland vegetation…and in general, become a functional wetland. The site is in the river’s floodplain, and I presume is likely to flood periodically. Time will tell.

If you visit the site, leave a comment about what you find! Or leave a question about wetland mitigation. Join the conversation…

Author: Paul Weihe

Associate Professor of Biology at Central College, traditional author (Textbook of Limnology, Cole & Weihe, 5th ed.; Waveland Press), and now...blogger!

3 thoughts on “When A Wetland Must Go.”

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