There are more than 250,000 rivers stretching over 3 million miles across the United States. These streams lead to countless more waterways that form an interconnected system of essential natural resources for communities, agriculture, and wildlife.
The decades of development that has allowed for the growth of towns and cities is now better understood for its unintended impacts on these natural systems, the people that rely on them, and the aquatic species that call them home.
Every year, millions of fish—many threatened or endangered—migrate between the ocean and the waterways that make up their native habitat. For many other fish species in inland states, this remarkable journey takes place wholly within freshwater systems. Altogether, these migrations—often triggered by seasonal changes—occur as fish seek out optimal conditions for spawning, feeding, or overwintering. It is a vital process to maintain healthy aquatic ecosystems and it’s a process that’s often challenged by infrastructure and habitat fragmentation.
Structures such as dams, culverts, and levees have long been recognized as barriers to fish passage. And while good progress has been made in removing this infrastructure where possible, waterway restoration has continued to evolve over the past few decades. Encompassing a broader approach, today’s restoration tactics better account for the full complexities of watersheds as well as the resilience of important infrastructure they’re connected to.
In this blog, we’ll discuss how a more holistic approach is being taken to restore waterways to their more natural state, protecting both habitat and human access to this vital resource.
What is Waterway Restoration?
Waterway restoration is the practice of returning natural systems to a condition more in-line with their natural state, creating and improving access to healthy water resources for communities and aquatic species alike. While true restoration is sometimes not possible in an urban setting, there can still be enhancements that restore at least a portion of the lost function.
Restoration work typically involves evaluation of geomorphic, hydrologic, hydraulic, and ecologic function as projects are planned and designed. Hydraulic modeling and hydrologic analysis calculate correct depth and velocity conditions, which can be used to better design systems that, for instance, target specific fish species.
Taken a step further, restoration design seeks to replicate how a stream might have naturally evolved in the absence of development. Stream simulation supports this aim by assessing natural geomorphic processes while also considering what’s currently impacting channel evolution and how it might change in the future.
Common Waterway Restoration Features
In support of communities, aquatic species, and healthier floodplains as a whole, there are a number of common features in waterway restoration design aimed at different goals.
Floodplain Reconnection
Regrading to raise the streambed, to lower the floodplain, or remove of infrastructure such as a tide gate, culvert, or levee allows a river to access its natural floodplain. This improves habitat availability and complexity, and floodwater storage.
Riparian & Wetland Enhancement
Planting native vegetation along streambanks helps to stabilize soil, filters runoff, and provides shade and habitat for aquatic and terrestrial species, and wetlands absorb floodwaters, filter pollutants, and serve as critical breeding grounds for fish and amphibians.
Channel Reconfiguration
Restoring natural channel form and processes (e.g., meandering/multi-threaded channel and pool, riffle, boulder/log step features) to improve flow dynamics, sediment transport, and habitat diversity.
Large Woody Material
Using woody material in stream restoration projects provides habitat where various types of fish—as well as insects they feed on—can live and thrive. Logs (with and without rootwads attached) and tree limbs are anchored along the banks to reduce erosion, add aquatic organism habitat (cover, resting areas), and support floodplain function. As the wood decays it also adds important nutrients to the water.
Removing or Improving Diversion Structures
Removing obsolete dams or retrofitting them with more resilient, fish-friendly designs restores connectivity, improves ecosystem health, and supports our community that relies upon this infrastructure.
Bioengineering Techniques
Using living plant materials in combination with natural and synthetic support structures, mimicking natural processes where erosion is most severe and bank stabilization is needed. This can include the use of riprap slope protection that is modified to incorporate elements of the other restoration techniques such as, inclusion of large woody materials or soil to support plantings.
Fish Barriers, Encroachment, and Water Quality
Over time, as restoration work has become more prevalent, along with the data to study and even adaptively manage its impacts, the field has continued to evolve. Restoration efforts today look beyond the removal of barriers alone to consider all factors that contribute to healthy systems, often requiring a more holistic approach that evaluates the entire watershed.
In addition to removing physical barriers, waterway restoration work now also accounts for encroachment on waterways from sedimentation and pollution as a part of overall water quality. This is an important step in understanding impacts to adjacent habitat and community infrastructure. Russ Gaston, Senior Vice President, Water & Natural Resources, has decades experience studying and improving fish passages, working in both the public and private sector. He explains, “for years, restoration projects focused mainly on removing physical barriers or helping fish pass through or around barriers. What we have seen though, is streams that had polluted water flowing into them did not achieve positive results after physical barriers were removed. Rather, they saw little to no improvement at all.”
For instance, even after over 20 years of work in the French Creek watershed of Snohomish County removing fish barriers, restoration of spawning salmon to the upper watershed remained impeded because the water-quality-barrier in the watershed had not been improved.
Since then, the team has worked with the county and farmers in the watershed to explore new options to both improve water quality and restore stream buffers in the agricultural lands. “We commonly focus on stormwater runoff and work to create a stable channel to keep bank erosion to natural rates, which are primary sources of pollutants in a stream. We also use the Benthic Index of Biotic Integrity (B-IBII) to project the health of the stream before and after the restoration is completed,” says Russ.
This more comprehensive approach to waterway restoration is a collaborative, multidisciplinary effort involving cities, counties, agencies, tribal consultation, and property owners to fully assess common goals. Consideration for regional stormwater management, water rights, connectivity of wetlands, and aquatic habitat are all incorporated into a design for lasting solutions.
A Multidisciplinary Approach to Resilience
To fully understand what is happening within a waterway and what barriers—physical or otherwise—are having the greatest impact, the entire watershed needs to be considered. This requires the expertise and perspective of a multi-disciplinary approach that ideally includes structural and civil engineers, geomorphologists, biologists, wetland ecologists, and landscape architects. Russ, who has witnessed changes in the industry firsthand, points out that it’s not just multiple disciplines weighing in on a project, it’s diverse perspectives working together. “What I thought was an integrated team years ago, is nothing compared to what we do today.”
Working closely together, integrated teams have a greater understanding of all aspects of a restoration project and how it will deliver greater resilience in current and future conditions. From leading the next generation of work in the Pacific Northwest to preparing watersheds for wildfire in the Mountain West, Otak has been at the forefront of this shift to a more holistic approach to improving fish passages. These multidisciplinary efforts not only aim for multi-species preservation but also work closely with various jurisdictions—cities, counties, the state— to maximize cost benefit for whole communities.