Background
A common claim of climate alarmists is that flooding becomes more frequent and severe in response to global warming; and as a result, whenever and wherever such a trend may manifest itself, radical environmentalists are quick to attribute it to anthropogenic CO2 emissions. But could there be other things behind such tendencies? This question was recently explored by Pinter et al. with respect to floods throughout the Mississippi River system of the United States.

What was done
To test for long-term changes in flood magnitudes and frequencies, the five researchers "constructed a hydrologic database consisting of data from 26 rated stations (with both stage and discharge measurements) and 40 stage-only stations." Then, to help "quantify changes in flood levels at each station in response to construction of wing dikes, bendway weirs, meander cutoffs, navigational dams, bridges, and other modifications," they put together a geospatial database consisting of "the locations, emplacement dates, and physical characteristics of over 15,000 structural features constructed along the study rivers over the past 100-150 years."

What was learned
Pinter et al. report that "significant climate- and/or land use-driven increases in flow were detected," but they say that "the largest and most pervasive [our italics] contributors to increased flooding on the Mississippi River system were wing dikes and related navigational structures, followed by progressive levee construction."

What it means
In discussing the implications of their findings, Pinter et al. write that "the navigable rivers of the Mississippi system have been intensively engineered, and some of these modifications are associated with large decreases in the rivers' capacity to convey flood flows." Hence, man has indeed been responsible for the majority of the enhanced flooding of the rivers of the Mississippi system over the past century or so, but not in the way suggested by the world's climate alarmists. The question that needs addressing by the region's inhabitants, therefore, has nothing to do with CO2, but everything to do with how to "balance the local benefits of river engineering against the potential for large-scale flood magnification."