Reconnecting Floodplains

Smarter floodplain management is about protecting the valuable services floodplains provide for people and wildlife.

(Download the fact sheet on smarter floodplain management)

Floodplains are the flat areas of land next to rivers — the nexus between water and land. By designing our cities with floodplains, instead of on top of them, we can reduce risks of flooding and property damage. Floodplains also recharge our groundwater, help clean our water, and provide open spaces for us play. They are the spawning grounds for fish and a refuge for birds. Healthy floodplains can also help communities become more resilient to the effects of climate change.

THE DANGER

As more homes, businesses, and roads are built within floodplains, the danger of flooding to people and property increases because rivers have nowhere to rise.

The costs of flood damage in the U.S. continues to increase, which can be devastating not only to property owners but for entire communities that absorb the cost of emergency services, lost business, sewage overflows, road closures, and cleanup. In many places, flooding is expected to become more frequent and severe due to climate change. Today, many of our floodplains are no longer healthy enough to buffer us from flooding or to support fish populations. These challenges add to the complex science and the changing regulatory requirements surrounding floodplains.

A PATH FORWARD

Willamette Partnership is creating a suite of strategies and tools that will help communities reduce their risk of flooding and improve floodplain health. Local governments, state agencies, private landowners, and local conservation groups can use these strategies to better manage floodplains.

6 Strategies for Smarter Floodplain Management

1. Land Use Planning

Where floodplains are still undeveloped, local land use planning should aim to steer new development away from high-hazard areas and away from areas with highly functioning floodplains. Functioning floodplains should be seen as an infrastructure investment. Where new development in floodplains is unavoidable, compensatory mitigation should be required to ensure that flood storage capacity, habitat for imperiled fish, and other natural floodplain functions are replaced.

As part of its response to litigation over floodplain development impacts on endangered fish, the Federal Emergency Management Agency created a model floodplains ordinance that may provide a good starting point for communities interested in this approach.

2. Watershed Restoration

From green infrastructure in urban areas to large-scale restoration efforts in less developed watersheds, many communities are working within existing developed land areas to restore the natural functions of floodplains. The Floodplains By Design program in Washington provides a promising model for public investment in floodplain restoration projects that provide multiple benefits, including improved water storage, fish habitat, support of working lands, public safety, and water quality.

For existing restoration efforts to scale up to restoring floodplains for more resilient communities, increased funding and tools will be needed to target where those investments can be most effective.

3. Structural and Nonstructural Solutions

Levees and dams can play an important role in protecting existing development from catastrophic floods, but they also impair beneficial floodplain functions. When levees fail, flood damage can be extreme, both because people behind the structures are often unaware of the risk and because the failed structures can retain water and prevent it from receding back into the channel. Because of these inherent problems, new flood protection structures should be developed only as a last resort for defending existing development and not in order to accommodate new development in high-hazard areas.

Nonstructural solutions such as maintaining floodplains as open space, buyouts of at-risk structures, or community planning and zoning for floodplain management are emerging as an important tool for helping to increase community resilience to floods and to restore floodplain function.

4. Design Standards 

Where new construction does occur in floodplains, the focus should be on designing buildings that can withstand the effects of flooding and on avoiding or minimizing impacts on flood storage, water quality, and fish habitat. Low Impact Development standards can help ensure these goals are met. Policy and insurance incentives for land elevation should be removed because they can increase flood risk to surrounding properties and can undermine habitat and other important natural functions.

5. Disaster Relief 

Where floodplains are already highly developed, hazard mitigation planning can help limit the risk to people and property. Communities should plan for what will happen when floods strike as well as think ahead as to how they will respond and rebuild after a flood. In areas that flood frequently, or where damage has been severe, voluntary buy-outs can be an important tool.

6. Community Awareness

Most people that live or work in floodplains are unaware of the risks they face or of the potential damage that floodplain development can cause to water quality, fish, wildlife, and other ecological values. When governments permit or even incentivize development in high-hazard areas, they can unwittingly send the message that they have evaluated the risk – both to public safety and ecological values – and deem it to be acceptable. Local governments, nonprofits, landowners, and state and federal agencies can work together to build community awareness of the importance of floodplains and a realistic understanding of the risks associated with building and living in floodplains.

– Strategies On the Ground –

TILLAMOOK COUNTY, OREGON

Tillamook County’s Southern Flow Corridor project (pictured below) proposes to restore 10% of the watershed’s historical tidal wetlands and remove or modify 10 miles of levees that currently constrain the river channel in order to improve endangered salmon habitat and reduce the frequency and intensity of flood events and associated damage.

Photo courtesy of Tillamook Southern Flow Corridor Project

PIERCE COUNTY, WASHINGTON

In response to repeated flooding, Pierce County is moving their flood management strategy away from the use of gray infrastructure, such as levees to channelize flood-prone rivers, and towards nonstructural solutions like buying out land and property in flood-prone areas. Their 2013 Rivers Flood Hazard Management Plan reflects the viewpoint that “fighting the river” is a costly and mostly ineffective way to protect human life and property.

The South Fork Road Floodplain Restoration project in Pierce County, pictured above, reduces flood risk and improves salmon habitat. / Pierce County, Wash.

TOOLS FOR NAVIGATING FLOODPLAIN SCIENCE & REGULATION 

Photo / U.S. Geological Service

Implementing these six strategies will look different in every community. Some may focus on voluntary buyouts in flood-prone areas, while others might invest heavily in restoration or in steering new development away from higher-risk areas. Likewise, each community faces its floodplain management challenges with a unique set of capacities and resources.

A common thread among many communities is a need for better information and management tools, including:

• Improved mapping of current and future flood hazard areas, including areas at risk from erosion and channel migration;
• Land use planning support, including tools that quantify natural floodplain functions in a way that can be used in benefit-cost analysis, prioritization decisions, and comprehensive planning; and
• Policies and programs that provide an integrated path for communities to meet the diverse set of regulatory requirements that come together in a floodplain, including the National Flood Insurance Program, the Endangered Species Act, and the Clean Water Act.

Some of these gaps may be most effectively filled at the state level so that each individual municipality does not need, for example, to invest in expensive mapping and modeling efforts. Willamette Partnership is working closely with a diverse group of partners to help fill some of these gaps in Oregon, with support from the U.S. Department of Agriculture’s Natural Resources Conservation Service.

Get in touch about your floodplain.

Have questions about smarter floodplain management?

Sara O’Brien, Executive Director
obrien@willamettepartnership.org
503.577.0421