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.
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