This article first appeared in the St. Louis Beacon: November 14, 2008 - A recent day-long scientific meeting and forum on floods offered diverse perspectives on why floods and flood damages are increasing, and offered helpful remedies. The Center for Environmental Sciences at St. Louis University brought together experts in hydrology, meteorology, engineering, conservation, biology and environmental law.
Among the major conclusions that are well supported by data and seemed to be accepted by practically all speakers are :
(1) Large floods have become more frequent on many streams and rivers. There are two components to this.
- Greater precipitation and more extreme storms have increased river discharge, and these effects will be amplified by global warming.
- River structures and floodplain developments have made damaging floods out of events that would once have been insignificant.
(2) Water levels on major rivers have increased to convey the same amounts of water. Channelization of the rivers, particularly wing dikes and the twofold reduction in width of many large rivers, can explain these effects in detail. Watershed changes that increase the rapidity of runoff delivery are more important on small streams than on large rivers.
(3) Floods that are geologically possible are much larger and less predictable than our short historical record would suggest. Even our calculated levels for "100-year" and "500-year" floods are seriously underestimated.
(4) Realistic economic structures are needed to reduce flood risk. Opportunities for improvement abound, especially given a future of increased meteorological and hydrological chaos. Flood maps, insurance rates, and zoning regulations need to be revised.
The upcoming reauthorization of the National Flood Insurance Program (NFIP) provides a special opportunity to rectify deficiencies.
Among the items that have been recommended are:
- Reconstructing wetlands and wildlife refuges
- Installing gates and spillways on levees
- Buying out homes and agricultural lands
- Enforcing existing laws
Remarkably, one contributor effectively challenged the notion that floodplains are worth more dry than wet!
Several universities, conservation organizations, state government, planning organizations and the private sector took part, but the Army Corps of Engineers declined to formally participate, while its $6 billion proposal for a comprehensive plan to build more levees and river control structures is pending before a lame duck Congress. Abstracts contributed by each of the 16 speakers are available online , and short papers contributed by those authors will be available early next year.
The prospects for increased flooding and meteorological chaos are daunting at a time of global economic stress. For our own nation and our region in particular, it is crucial that we thoughtfully and collectively revise our course.
Robert Criss is a professor in the department of Earth and Planetary Sciences at Washington University. He is the coauthor of the 2003 book, "At the Confluence: Rivers, Floods, and Water Quality in the St. Louis Region," and was one of the organizers of the conference at St. Louis University.