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Does the Fate of Iowa’s Lake Delhi Offer Glimpse into Future?

July 27, 2010Patrick NunnallyRivers, UncategorizedComments Off on Does the Fate of Iowa’s Lake Delhi Offer Glimpse into Future?

In eastern Iowa, Lake Delhi, a nine-mile long impoundment in the Maquoketa River, disappeared this weekend after heavy rains caused a dam to burst.

Read the story and view video and photographs from the Des Moines Register here.

Make no mistake, this is a sad story, and the loss of property will add more economic hardship to flooding damages that eastern Iowa has suffered over the past three years.

But it seems to me that there are several threads to this story that warrant attention, and that raise policy questions for our future lives on and near rivers.

For one thing, the Governor is quoted as saying that he’ll marshal all the resources he can manage to restore the lake and help people get back on their feet.  He is expected to say such things; if you read farther into the story, you see similar views expressed by other elected officials.  But the staff of water management agencies add a more nuanced tone, as they talk about building a new dam to higher standards, and perhaps about including hydroelectric generating capacity in a new facility.

Another important theme to the story is not addressed in the newspaper at all:  potential for floods comparable to this one to recur in the future.  Northeastern Iowa received heavy rainfall over the weekend, adding to already-saturated soils and swollen rivers and streams.  Maybe this was just another case of a freak storm, and “act of God” that can’t be predicted.

But close observers of climate changes indicate that these storms may not be so freakish at all, and that increased “severe weather events” may be part of a pattern associated with a changing climate.  University of Minnesota professor and state climatologist Mark Seeley has studied data over six decades and reports a pronounced increase in heavier rainstorms which seem to occur later in the year than they had in the past. (Note:  I am reporting Prof. Seeley’s conclusions from my memory of a talk he gave last January; please check thoroughly the link above for more detail.)

Meanwhile, researchers in engineering at the University of Iowa’s Iowa Flood Center are working to monitor and predict river flow more precisely.  Their hope, as expressed by Dr. Larry Weber, is to be able to map the hydrology of storms precisely, combining detailed knowledge of land use, land cover, and the prevalence of drain tile in farm fields to get a better idea of how much, and how quickly, rain water moves off the agricultural landscape. 

Finally, the wall of water that Lake Delhi became as it swept downstream is headed straight for the Mississippi River and communities downstream such as the Quad Cities are bracing for a sudden flood.  This flood will be later than the usual spring flood season, and there is very little warning time for cities to get their defenses in place.

Maybe this is just the kind of thing that we all have to get used to.  But the incidence of large floods is increasing, and all the indicators point to continued increases. 

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