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“Rivers will do what rivers do.”
Floodplain Management: A New Approach to a New Era outlines a new paradigm for flood management, one that emphasizes cost-effective, long-term success by integrating physical and biological systems with our societal capabilities. It describes our present flood management practices, which are often based on dam or levee projects that do not incorporate the latest understandings about river processes. And it suggests that a better solution is to work with the natural tendencies of the river: retreat from the floodplain by preventing future development (and sometimes even removing existing structures); accommodate the effects of floodwaters with building practices; and protect assets with nonstructural measures if possible, and with large structural projects only if absolutely necessary.
Rivers will do what rivers do. Historic flooding of the Mississippi River shows that our approach to flood control hasn’t worked and can have effects far beyond the limited area of a floodplain. The consensus of scientists around the world is that we are in a period of rapid global climate change, which makes working with rivers–instead of against them–increasingly important. Some places will get more intense rainstorms, while others may get less frequent summer rains. Still other areas may get winter storms with less snow and more rain, producing immediate runoff instead of storing water for spring. These coupled with increases in ground cover and other changes may increase flooding, and, in some cases, may also increase drought.
We are inviting you to share cases studies or projects that demonstrate a rethinking of traditional approaches. Our book offers examples. Do you know of others? Examples where:
- Levees have been removed or relocated
Levee systems often prevent our exploitation of natural beneficial functions such as storing water, processing pollutants, increasing productivity of the land. Where have levees been removed or relocated away from the channel? Where has water been routed over floodplains and not restricted to channels?
- Communities have designed built environments that accommodate surface flooding
We cannot and should not eliminate all overland flooding. Are there examples of communities adapting to and living with flooding?
- Natural upland depressions and retention opportunities have been exploited
Snow and ice do a great job of storing water: assuring summer flows and tempering winter discharges. What projects have proven successful through changes in landcover, development of off channel depressions, spreading water throughout the floodplain, expanding the floodplain… to replacing functions being lost?
- Communities have adopted managed tools that limit quick flush alternatives
Where have downstream interests supported beneficial upstream actions? Where have buildings (especially large “Box” structures) been elevated without the use of fill?
Water detention is becoming increasingly important as our changing climate produces more intense winter storms and periods of summer drought. Yet, detention faculties can be attractive and contribute to the enjoyment and enrichment of our everyday life. Community benefits can exceed those provided solely through holding water. Here is one example designed by Herbert Bayer.
Herbert Bayer survived the Austro-Hungarian Empire studied at the Bauhaus, art-directed Vogue in Weimar Germany, and was included I the Nazis’ notorious 1037 “Degenerate Art” exhibit before fleeing to the US. And today part of his legacy resides in Kent. One of his last endeavors was designing the 1982 Mill Creek Canyon Earthworks, a stormwater containment project sited in a ravine just east of downtown Kent. For more information go to: http://www.ci.kent.wa.us/arts/page.aspx?id=2152
The Chehalis Washington Home Depot and Kmart are installing flood barriers to prevent flood damage as reported by Carly Nairn of the Lewis County Washington Chronicle this January 2, 2010.
This is response to the 2007 flood that put the Home Depot under 18 inches of water costing millions of dollars.
There will be greater real dollar costs above and beyond the direct costs in installing these barriers — Costs to Chehalis and costs to their up and downstream neighbors.
These structures are here now and certainly have the right to protect their businesses and their protection will provide an initial direct benefit to Lewis County. However there is no free lunch.
- The presence of these large structures including their parking lots will cause future flooding
The Home Depot store manager Brian Sperber, as noted in the above mentioned article recognized that stores such as Home Depot are in floodplain and that they contributed to increase flooding in 2007.
- Down and upstream communities will have to deal with increased depths, greater velocity, less time to prepare… The downstream communities of Centralia, Rochester Oakville, and Elma along with unincorporated lands will have increase costs. As will upstream communities.
Our climate is warming, bringing increased winter rain amounts and increases in intensities within the Chehalis River valley. Summers will be dryer. As a direct result of these structures natural floodplain storage benefits will be reduced. In the summer the ground water table will be lower and in the winter the flood heights and flood duration will be greater. There will be decreases in farm productivity and an increase need for flood protection. And there are a host of other effects – increased sediment, forest fire risks, less productive lands….,
Impact on sports and commercial fishing will be felt. As water spills over onto the floodplain it seeps into the ground where it is processed. Pollutants are filtered and eaten by small plants and animals as the water works its way back into the river and on to the ocean.
These stores are here and the community is benefiting. However new development should be located off the floodplain. And, compensating approaches should be installed to mitigate the adverse impacts of these structures such encouraging wet gardens, installing vegetated detention areas, replacing parking areas with impermeable surfaces ….
We must look for new approaches to floodplain management.
Larry Kunzler
In Skagit County, as a member of the Flood Control Zone District Advisory Committee, I can tell you it (removing levees) will go nowhere. I’m all in favor of it but the farmers don’t even want to go to overtopping levees let alone levee removal. There used to be this old timer who would show up for every flood meeting, he’s passed away now, and he would tell the room full of people that they would all be better off without the levees. I got his testimony in some of the public hearing transcripts on my web page (http://www.skagitriverhistory.com). He was absolutely right, but the Ag. people just won’t buy into it. Nothing is going to happen in Skagit County until the:
- Government (namely FEMA Region X) starts enforcing the NFIP local ordinances.
- Corps changes it policies that levees are the answer.
- Congress has to quit funding levee projects unless they include the element of overtopping at less than 100 year event levels.
- The state of Washington has to take back the authority to issue floodplain permits from local governments. Putting local governments in charge is like putting the fox in charge of the hen house.
Harold Smelt, Pierce County Washington.
The Soldier’s Home Setback Levee project restored about 67 acres of Puyallup River floodplain to historic pre-levee conditions. The original levee was removed to the water line and a new levee was built 950 feet back from the river allowing the river to naturally meander within the reclaimed floodplain providing increased flood protection to adjacent property and natural benefits to the greater community.
To ensure flood protection, the setback levee project included the fortification of levees downstream, across, and upstream of the setback levee and involved placing additional rock rip rap to the existing levee face and toe, and raising the levee in places.
The set back levee was built with re-used material that was blended with new material.
Habitat channels were dug to expedite reclamation.
Protecting I-5 and residents occupying the Chehalis River, Washington floodplain may provide an opportunity offer additional benefits.
In Chapter 8 of Floodplain Management we offer a case study concerning protecting Interstate 5 from flood damage.
For those who have not read the chapter during the first week of December 2007, record-setting precipitation dumped on the Pacific Northwest. Torrents of water-gouged hillsides broke levees and overtopped dikes as floods reached record highs. One man was swept away in the deluge. The I-5 freeway in Lewis County, Washington was closed for three days and traffic was rerouted an extra 400 miles. The Department of Transportation estimated the cost of the I-5 closure exceeded $4 million per day.
The Chronicle (Lewis county Washington) editorial board in “OUR VIEWS: Our State Reps Push for Water Retention” (October 30, 2009) stated that water retention deserves a chance if studies bear out its effectiveness. And beyond flood protection, water retention has the possibility of improving water quality in the river, enhanced fisheries, agricultural benefits and expansion of recreation. Currently the Army Corps is only focusing on building 11 miles of levees that might protect Interstate 5 during big flooding events, and perhaps parts of the Twin Cities, but certainly would not help out in other areas along the Chehalis River
Not mentioned were expected impacts from Climate change. The Climate Impact Group (CIG) and the International Panel on Climate Change (IPCC) project increases in winter rain quantity and intensity leading to greater flooding. And, increasingly, summers will be hotter and dryer contributing to drought. These changes are being notice now.
Retention alternatives could reduce winter discharges while increasing summer ones.
Can flood reduction efforts resulting from the 2007 incident be viewed as an opportunity to address expected climate change impact?
