Rescuing the valleys: a new approach to flooding, endangered salmon, and crumbling dams

A book by UW professors offers smarter ways to treat the rivers around which we have built civilization. Following their ideas might help assure our civilization, in a future where we work better with nature at less cost.

Crosscut archive image.

Engineers check the Howard Hanson Dam in March 2009.

A book by UW professors offers smarter ways to treat the rivers around which we have built civilization. Following their ideas might help assure our civilization, in a future where we work better with nature at less cost.

Floodplains are where the rubber hits the road, or more to the point, where the water hits the land. Whether it’s the Duwamish, Green River, Snoqualmie, Nisqually, or Skagit valleys, we all live near or around river valleys and their associated floodplains. Who would have thought that floodplains would be the site of an innovative new approach to infrastructure dealing with everything from environmental restoration and salmon recovery to healthier Orcas in the Puget Sound, water quality, and the Howard Hanson Dam?

This cutting edge approach is detailed in a brilliant book with a boring title, Floodplain Management: A New Approach for a New Era, by a diverse team of mostly University of Washington professors. Authors Robert Freitag, Susan Bolton, Frank Westerlund, and J.L.S. Clark bring together their individual expertise in hazard mitigation planning, forestry, urban design, and geology to provide a book that is eminently practical. Weighing in at less than 250 pages, the book is full of fascinating real life case studies and a method to help communities make the best plans for watershed stewardship and infrastructure planning.

This book is part of a deep tradition in ecological regional and city planning. In 1969, the renowned planner and landscape architect Ian McHarg wrote the seminal classic Design with Nature. McHarg sought to propose healthful land-use patterns based upon understanding the unique geology, topography, natural, and cultural features of a given landscape. What McHarg painted in broad brushstrokes, the authors have rendered in fine detail in a book that would have surely won his praise.

The book offers important new ways of dealing with issues that face Seattle, the Puget Sound region, and the state of Washington. Most of the questions, like flooding, drought, and salmon recovery are heightened by climate change. The book's advice has wide relevance for many questions, including the costs of infrastructure repairs or replacements for aging fixtures like the Howard Hanson Dam on the Green River.

Before diving into the book, it is important to get sufficiently "hydrated" about why one should give a damn (not "dam") about floodplains in the first place. This is best achieved by showing how floodplains have been the cradle of civilization as well as a marvelous system of "natural" infrastructure.

Infrastructure is where nature and civilization meet; nowhere is this more evident than in the floodplain. Human civilization grew up in the river valleys along the Tigris and Euphrates in Mesopotamia (literally the land between the rivers), the Indus River in India, the Yellow River in China, and the Nile River in Egypt. Floodplains are flat and occasionally flooded over by rivers that fertilize the soil with alluvial deposits, making an ideal place for the birth of agriculture. The first large infrastructure projects were for irrigation to trap and distribute flood waters.

The agricultural bounty secured by irrigation systems allowed for the development of wealthy civilizations with flourishing cultural centers. River systems also provided drinking water and abundant fish stocks and served as the main transportation corridors before railroads and highways.

To this day, most cities are located on or near a river. Seattle is located at the mouth of the Duwamish River, Portland is bisected by the Willamette River, and Vancouver is located at the mouth of the Fraser River.  Agriculture is still tied to rivers as shown by the wheat fields and orchards of Eastern Washington fed by the Columbia River.

Civilization arose from the floodplain because it is the heart of a vital circulatory system composed of rivers and fed by glaciers and rain. The watershed is truly the "body" of this entire system and to understand its importance one must follow the journey of what author Timothy Egan called the "good rain."

In a pristine watershed, most water is absorbed into the ground and replenishes rivers, aquifers, and groundwater. Rivers transport glacial grindings that fertilize valleys and build up beaches. An untamed river runs like a sinuous ribbon across the landscape, constantly doubling back on itself — this meandering shape slows the water down, provides valuable habitat and spreads water over the land. Of America’s 3.5 million miles of river, only 2 percent are in this relatively undisturbed state.

Floodplains can be viewed as both a giant sponge and a filter — as sponge they can store tremendous amounts of groundwater, as filter they cleanse a wide variety of pollutants. In an undeveloped valley only 10 percent of the water is surface runoff, the rest is absorbed into the ground or evaporated. In a highly developed valley, 55 percent of the water is surface runoff. This excess runoff would cause major flooding if not channeled by a vast human-made network of drains and pipes to the nearest water-body or sewage treatment plant.

The treatment plant is important because stormwater is more polluted than toilet water. Rain water flowing over roads, driveways, and lawns picks up motor oil, chemicals, and fertilizers to form a toxic cocktail only an Orca must drink. The undisturbed riverine system truly has an amazing ability to filter and cleanse most of this pollution. But many rivers have been caged behind levees and dams, routed in Cartesian concrete channels and pipes, and many floodplains have been covered over in asphalt.

Climate change makes life on the floodplain even more complicated. Snow pack that once stayed frozen is now flooding rivers during the winter months with correspondingly smaller summer melts when water is needed most. The shrinking and future disappearance of the Himalayan glaciers due to climate change impacts major river systems in both China and India. Societies are only beginning to grapple with the stresses to communities, businesses, farms, forestland, and wilderness.

It is from this deep understanding of the floodplain that the authors of Floodplain Management propose solutions the work with nature and evolve beyond the "one size fits all" approach of the past century. As they write, “Where the 20th century was the age of big projects like dams and levees, the 21st may see a dismantling of many of these projects to use the natural advantages of riverine processes.”

Most Americans got a front-seat at the clash between big infrastructure and nature when Hurricane Katrina touched down in New Orleans. For more than a century, the U.S. Army Corps of Engineers has fought to tame the mighty Mississippi River by impounding it in channels behind ever rising levees. Development sprawls behind the false safety of these levees. The sprawl increases runoff and makes the river fiercer during flood season while putting more people in harm’s way. This is the design-against-nature method and requires a veritable army of Tom Thumbs.

The continual heaping up of levees means that when failure does occur, it is catastrophic and unimaginably expensive both in human and ecological costs. The Central Valley in California is another tale of aging levees and unwise land-use practices. In 1997, levees ruptured, inundating 300 square miles of land; 48 counties were declared disasters areas, 148,000 people evacuated, and $7 billion in damages resulted. Those levees are still failing and the potential threat posed to the Sacramento area alone could be upwards of $25 billion in direct damages.

To rebuild and maintain all this infrastructure would be insanely expensive and only make the day of reckoning worse. The authors offer a new way of managing risk and making intelligent, long-range, cost effective choices. They differentiate between the "structural" and "non-structural" approach to managing floodplains.

The structural approach uses more concrete than the Seattle’s old Kingdome Stadium to build large dams and levees. Although some of these projects can be appropriate in certain locations, they dramatically alter the landscape and ecology at mammoth cost. The "non-structural" approach works with the river through land-use, building codes, low impact development, conservation, and the strategic placement of infrastructure.

The book provides many case studies where this approach has been highly successful. In New York, the Catskills Mountains provide 1.3 billion gallons of water daily to 9 million city dwellers. The purity of Big Apple drinking water was threatened by development and agricultural runoff. The state could have spent $7 billion dollars to build new filtration facilities with annual operating costs of $400 million. Instead, the state chose to purchase and conserve over 52,000 acres of the upper watershed for $131 million. The unimpaired natural systems are more effective and far less expensive at cleansing water than a new treatment plant. As the authors say, “Our emphasis must be on preserving or enhancing natural risk-reducing processes.”

These methods can be equally applied in Washington state’s own backyard. Closer to home, the seemingly imminent failure of the Howard Hanson Dam in the Green River Valley was a top news story in late 2009 and early 2010. During the height of flood season, the odds were as high as a 1-in-3 chance of the dam’s failure. The dam has been "repaired" to now withstand a 70-year flood, but dams are usually built to withstand a 500 to 1000-year historical flood. But as natural catastrophes and climate change are proving, infrastructure is being pushed to the max on an alarmingly frequent basis.

Following the book’s approach, several strategies can improve the resiliency and safety of the overall system (both natural and constructed.) Setting levees back from the channel and creating break-out points for holding ponds would restore some of the water storage and filtering functions of the floodplain while providing valuable habitat and lovely recreation areas. Although the upper watershed is narrow, it is worth studying whether additional storage capacity can be created for holding peak storm loads, thereby reducing pressure on the Green River dam.

Updated building codes can foster "flood-tolerant" construction practices such as elevating buildings so that flooding would cause minimal damage — a strategy that has been successfully used nearby in the Snoqualmie Valley. Rivers are meant to flood and development can accommodate this reality. This approach would avoid costly property damage and draining public coffers to build ever-larger structures to barricade the river.

The implementation of low impact development methods would increase pervious surfaces and help property owners to deal with stormwater on site. Finally, land-use planning would encourage development in areas not impacted by flood waters while discouraging various uses in areas that are under threat. Holland is a superb example of a country that marries top-notch infrastructure design with effective land-use planning, which funnels development away from danger zones.

If this approach is carried out, one can imagine a time when Green River residents no longer live in fear of losing life and limb beneath an aging dam. The risk of flood damage would be significantly reduced and valuable habitat would be regained within the valley. With cash strapped state and local governments, elected officials would feel confident in a solution that was less costly and more resilient while providing environmental restoration and community amenities.

It doesn’t get much more basic than clean water and the myriad ways it serves life. We all live in the watershed, many of us live in the floodplain and all of us depend on the vital services, bounty, and beauty provided by the river valley. Yet to understand the fate of the floodplain one need only head south on Interstate 5 along the rim of the Duwamish valley.

This once-vast floodplain that runs between the rim of Beacon Hill and West Seattle is now covered over with a host of industrial uses, airports, highways, and residential development. Many benefits have accrued from these uses, yet much has been lost, and much of this development occurred before the function of floodplains was well-understood.

In an increasingly urbanized world where major cities abut rivers, the protection and restoration of floodplains will be crucial for the health of our society. Floodplains are the cradle of civilization, and with this valuable book we can ensure they do not become its grave, perhaps beginning to insure a healthy future by applying the concepts here at home.


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