As experienced flood control specialists, we understand the critical importance of integrated, nature-based approaches to floodplain management. In the face of escalating climate risks, restoring the natural functions of floodplains offers a powerful solution to not only mitigate flood impacts, but also enhance ecological resilience and deliver multiple community benefits.
Now, this might seem counterintuitive…
Understanding Floodplain Dynamics
Floodplains are the low-lying areas adjacent to rivers, streams, and other waterways that are periodically inundated during high flow events. These dynamic landscapes play a vital role in the overall health and functioning of aquatic ecosystems. When allowed to operate naturally, floodplains:
- Absorb and store floodwaters: The porous soils and vegetation in floodplains act as natural sponges, slowing the flow of water and reducing downstream flood peaks.
- Replenish groundwater supplies: Floodwaters that spread across the floodplain can infiltrate the soil, recharging aquifers and supporting base flows in rivers and streams.
- Support diverse habitats: Periodic flooding creates a mosaic of wetlands, side channels, and other aquatic features that provide critical spawning and rearing grounds for fish and wildlife.
- Maintain water quality: Floodplains filter out sediments, nutrients, and other pollutants, helping to maintain the overall health of the waterway.
Unfortunately, decades of human development and flood control efforts have severely degraded many of the world’s floodplains. Levees, dikes, and other structural measures have confined rivers, disrupting natural flooding patterns and cutting off vital connections between the waterway and its surrounding landscape.
The Rise of Floodplain Restoration
In recent years, a growing movement towards floodplain restoration has emerged as a holistic approach to flood risk management and ecosystem enhancement. By removing or setback flood control structures, restoring natural river dynamics, and reestablishing floodplain connectivity, these innovative projects aim to:
- Reduce Flood Risks: By allowing rivers to access their historic floodplains, restoration efforts can reduce the height and duration of flood peaks, protecting nearby communities and infrastructure.
- Enhance Ecological Functions: Restoring natural flooding regimes can revive critical habitats, support biodiversity, and strengthen the overall resilience of aquatic and riparian ecosystems.
- Provide Multi-Benefit Solutions: Many floodplain restoration projects also incorporate recreational amenities, agricultural preservation, and other community-focused elements, delivering a diverse array of social and economic benefits.
One shining example of this approach is the Floodplains by Design initiative in Washington state. Led by the Washington State Department of Ecology and the Bonneville Environmental Foundation, this ambitious public-private partnership has been investing in large-scale, multi-benefit floodplain projects across the state since 2013.
Floodplains by Design: A Pioneering Approach
The Floodplains by Design (FbD) program recognizes that effective flood management cannot be achieved in isolation. By taking an integrated, ecosystem-based approach, FbD projects address a range of interconnected challenges, from reducing community flood risks to restoring critical habitats and supporting local economies.
Some of the key strategies employed by FbD projects include:
Levee Setbacks and Removals
One of the hallmarks of FbD projects is the strategic relocation or removal of flood control structures like levees and revetments. By setting back or eliminating these barriers, floodplains can be reconnected to their adjacent rivers, allowing for the natural ebb and flow of floodwaters. This not only enhances flood storage capacity but also restores the dynamic processes that sustain diverse habitats and ecosystem functions.
The Lower Russell Levee Setback Project in Kent, Washington, is a prime example of this approach. By upgrading 1.4 miles of levee and revetment to withstand a 500-year flood event, the project ensures long-term resilience for the region while also revitalizing the local environment and enhancing community spaces.
Floodplain Reconnection
In addition to levee setbacks, FbD projects often focus on restoring the physical and hydrological connections between rivers and their floodplains. This can involve removing barriers, excavating new side channels, and strategically breaching or lowering existing berms and dikes. These interventions allow floodwaters to spread out across the landscape, recharging wetlands, restoring natural flow regimes, and reviving critical habitats.
The Nooksack River: Floodplains that Work project in Whatcom County, for example, is a multi-phase effort to integrate flood hazard reduction and salmon recovery with the needs of agriculture and other land uses within the Nooksack River watershed.
Habitat Enhancement
Floodplain restoration projects often include targeted efforts to enhance aquatic and riparian habitats. This can involve measures such as installing large woody debris structures, creating off-channel refuges for fish, and planting native vegetation along streambanks. By restoring the natural complexity and diversity of the floodplain environment, these interventions help to support a wide range of species and strengthen the overall resilience of the ecosystem.
The Puyallup Watershed Floodplains for the Future project, for example, is restoring 2.5 miles of natural riverine processes by reconnecting up to 37 acres of floodplain and preserving up to 350 acres of farmland throughout the Puyallup River watershed.
Integrated Community Planning
Recognizing that floodplain management cannot be achieved in isolation, FbD projects emphasize inclusive, community-driven planning. This involves actively engaging with local stakeholders, including residents, business owners, agricultural producers, and Tribal nations, to double-check that that project goals and strategies align with the diverse needs and priorities of the community.
The Community Floodplain Solutions project in Snohomish County, for instance, is a multi-faceted effort that includes acquiring vulnerable properties, implementing agricultural resilience measures, and enhancing trail and water conveyance systems – all with the aim of increasing ecological functions, reducing flood impacts, and protecting farmland productivity.
Unlocking the Potential of Floodplains
By embracing the natural power of floodplains, FbD and similar initiatives are demonstrating how innovative floodplain restoration can deliver a triple win for communities, ecosystems, and the economy. These projects not only reduce flood risks and enhance environmental resilience, but also create opportunities for recreational amenities, agricultural preservation, and other community-focused benefits.
As the impacts of climate change continue to intensify, the need for holistic, nature-based flood management solutions has never been more pressing. By learning from the successes of the Floodplains by Design program and other pioneering efforts, flood control specialists can help communities across the country unlock the immense potential of their floodplains, ushering in a more sustainable and resilient future.
To explore the latest advancements in flood control and water management, be sure to visit Flood Control 2015 – your go-to resource for expert insights, cutting-edge technologies, and best practices in the field.
Tip: Regularly inspect and maintain flood barriers and drainage systems
