You are here

Floodplain Restoration in the Willamette Basin

Floodplains and riparian forests are some of the most dynamic zones of any landscape, and they contain some of the highest levels of biological diversity and habitat complexity. These areas also are highly valued for their access to water, transportation potential, food, recreation, and beauty. Historically, towns and cities along rivers have encroached on this zone and then attempted to create stable stream banks in areas that are, by nature, dynamic. This inherent contradiction is the basis for management of floodplains and riparian forests worldwide.

Land use and other human activities in the Willamette River Basin have extensively modified rivers and their floodplains. Most restoration efforts are based on opportunities such as willing land owners, public lands, and short-term funding sources. These projects often lack a broader strategic framework based on both the ecological resources of the river and future pressures to develop land along the river. As a result, attempts to modify rivers or "restore" river systems often fall short of their goals.

Although restoration efforts based on short-term opportunities are not undesirable, their success can be increased by application of a strategy which considers ecological potential and patterns of human activity within the river corridor. Ecologically designed restoration efforts commonly are based on vegetation patterns, hydrology, geomorphic processes, or floodplain dynamics. These approaches tend to focus on the biological or physical components of rivers but rarely consider the human activities that shape the potential for ecological recovery and create future pressures to modify the river ecosystem. Patterns of human population densities and structural development, as well as economic values and productivity of the land along rivers, create critical constraints on the locations and outcomes of restoration.

Restore river floodplains. Riparian areas are more than trees along the river. Floodplains are dynamic places where water floods then recedes, where trees fall down, islands and channels are reshaped, and river junctions move across the landscape. Removing rip-rap and dams will free the river and allow the historic natural processes that support a healthy ecosystem to return. At a minimum, manage reservoir releases to mimic the natural seasonal high and low flows.

Let the river move gravel and silt around. Plan your local restoration project with this in mind so that it is not destroyed by the river's natural actions.

Restore low-cost, high-return areas of the Willamette River. The best areas of the river and its floodplain to restore are those that have highest potential for recovery of complex, biologically diverse habitats and where people are likely to be supportive. Seek areas where people haven't invested in buildings or changes to the land.

Don't build in the floodplain. Minimize development in 100-year floodplains and find opportunities to remove buildings and other structures.

Let the river cool itself. When the river flows through gravel, important chemical changes take place and the water temperature drops. If we encourage the river to flow more freely through islands, alcoves and gravel bars, it will increase habitat for aquatic creatures and improve water quality.

Conserve water. We need to decrease our water consumption if we are serious about protecting and improving stream flows for fish and wildlife.

Find ways to voluntarily convert out-of-stream water rights to in-stream water rights while maintaining their original priority date. We need to get water back into our streams. Some streams are over-tapped to the point that they will likely go dry in dry years. These include small streams in the Deep Creek, Molalla, Pudding, and Tualatin watersheds.

Sources

Willamette Basin Alternative Futures Analysis. Pacific Northwest Ecosystem Research Consortium, August 2002. EPA EPA 600/R-02/045(a).

Willamette River Basin Explorer Maps -- Floodplain Restoration

randomness