Every year, hundreds of muscular, sea-bright fish—chum salmon, chinook, coho, steelhead—push into the Columbia River from the Pacific Ocean, swim over 200 kilometers upstream, and turn left into Hardy Creek. They wend through rocky shallows shaded by alder and willow, cold water passing over flared gills. Plump with milt and eggs, they pump their tails furiously, striving for the graveled spawning grounds in southern Washington State where they’ll complete their life’s final, fatal mission.
And then they hit the railroad.
In the early 1900s, Hardy Creek was throttled by BNSF Railway, the United States’ largest freight railroad network. When the company built its Columbia River line, engineers routed Hardy Creek under the tracks via a culvert—a 2.5-meter-wide arch atop a concrete pad. The culvert, far narrower than Hardy Creek’s natural channel, concentrated the stream like a fire hose and blasted away approaching salmon. Over time, the rushing flow scoured out a deep pool, and the culvert became an impassable cascade disconnected from the stream below—a “perched” culvert, in the jargon of engineers.
“It’s an obvious barrier,” says Peter Barber, manager of the Cowlitz Indian Tribe’s habitat restoration program. “A fish would be hard-pressed to navigate through that culvert.”
The strangulation of Hardy Creek is an archetypal story. Culverts, the unassuming concrete and metal pipes that convey streams beneath human-made infrastructure, are everywhere, undergirding our planet’s sprawling road networks and rail lines. Researchers estimate that more than 200,000 culverts lie beneath state highways in California alone, nearly 100,000 in Germany, and another 60,000 in Great Britain. In Europe, they thwart endangered eels; in Australia, they curtail the movements of Murray cod. In Massachusetts’ Herring River, snapping turtles lurk in culverts to devour passing fish, largely preventing herring from spawning. Taken as a whole, these obstacles are a major reason that three-quarters of the world’s migratory fish species are endangered.
Compared with dams, however, culverts have historically escaped public attention; most people drive over them every day without noticing. “I used to tell people I assess culverts,” recalls Mark Eisenman, a planner at the Alaska Department of Transportation. “They’d say, what the hell’s a culvert?”
In 2022, however, the US Federal Highway Administration launched a US $1-billion program to replace culverts that block oceangoing fish on streams like Hardy Creek—among the largest pots of money ever devoted to these humble pipes. Fixing the countless barriers that underlie infrastructure, according to Barber, is “one of the best ways to restore our salmon runs locally.” But given the sheer scale of the culvert crisis, even a billion dollars will only go so far. Can we repair our faulty culverts while there’s still time to save sea-run fish? (...)
In 2021, the United States’ culvert-funding shortfall caught the belated attention of politicians. That November, Congress passed the Infrastructure Investment and Jobs Act, a $1.2-trillion package that included money for everything from high-speed rail to electric vehicle charging stations to basic highway repairs. Tucked deep in the law’s thousand-odd pages was a section that attracted little media coverage, but had immense consequences for fish: the National Culvert Removal, Replacement, and Restoration Grant Program. (...)
Mud Creek also illustrates another deficiency of culverts: they frustrate human movements as well as fish migration. Several times a year, says Golden, incoming storm surges overwhelm the Mud Creek culvert and gush onto Montague Island Road, damaging its surface and denying locals access to their homes. This is an increasingly common predicament. Culverts, already the Achilles heels of road networks, are becoming even more vulnerable as the climate changes. They’re swamped by king tides, clogged by landslides, and battered by deluges; during 2011’s Tropical Storm Irene, roughly 1,000 culverts washed out in Vermont alone, closing many roads. The same enlarged culverts that help fish are also less liable to get plugged by debris or inundated by storm surges. “We can address a maintenance need, a fish passage need, and a resilience need, all at the same time,” Golden says.
Perhaps the most powerful virtue of culvert replacement is that it fundamentally reconnects land and sea. Fish-blocking culverts are forces of disunity that prevent anadromous fish from contributing their oceanic phosphorus and nitrogen to forests, and starve marine predators dependent on healthy stocks. In western Washington’s King County, for example, culverts within the Bear Creek basin have curtailed populations of chinook salmon, a key food source for Puget Sound’s beleaguered killer whales. A grant of nearly $7-million will allow the county to replace three inadequate Bear River culverts—and, with luck, restitch the torn linkages between marine and terrestrial environments.
“We’re allowing those ocean nutrients to once again go up the watershed,” says Evan Lewis, who leads the county’s fish passage restoration program. “Salmon are self-propelled bags of fertilizer.” (...)
Around the world, other countries are also kicking lousy culverts to the curb. In France, faulty culverts have been torn out for the sake of Atlantic salmon and brown trout; in New Zealand, they’ve been removed for smelt, eels, and torrentfish. In British Columbia, home to more than 90,000 fish-blocking culverts, a host of conservation groups and government agencies is developing a strategic plan to remove the most egregious blockages. The United States is leading the charge, but its $1-billion culvert replacement program is no piscine panacea. The Washington State Department of Transportation recently estimated that it would cost around $7.5-billion to deal with the hundreds of fish-blocking culverts it’s required to fix on behalf of Indigenous tribes—to say nothing of perhaps 20,000 more on roads owned by counties, towns, and private entities.
The program is also limited by geography. Although the only culverts eligible for funding are those that obstruct sea-run fish, many landlocked species also migrate. In the Great Lakes region alone, perhaps 250,000 culverts confound suckers, pike, brook trout, and other freshwater denizens. These fish won’t benefit from federal largesse, yet they need help as surely as any coho or chum.
by Ben Goldfarb, Hakai Magazine | Read more:
Image: Maggie Chiang
[ed. In Alaska, culverts were a major headache. We had staff at the Alaska Dept. of Fish and Game who spent years assessing impacts on fish populations, trying to find solutions (scientifically, politically, economically) to mitigate the damage they cause. Here are a few examples of their effects: creating impenetrable barriers to fish passage when debris gets washed downstream and lodged at their openings; becoming perched several feet above streams due to discharge scouring from flood events (or initial bad engineering); designed too narrow so that water velocities exceed the swimming capabilities of young fish (fire hose example); and frequently becoming magnets for predators (including humans) who find pooled fish in a single location easy pickings. Migrating salmon are famous for their spawning imperative and endurance - I did a fish survey in Anchorage one time that found coho salmon fry upstream of a culvert that stretched half way across the city under numerous roads, business parks and subdivisions - over a quarter mile long. But, only a handful of fish could have survived that gauntlet, and I didn't find many fry in that sample. This is a massive problem, not only because there are so many culverts in fish streams (in various stages of disrepair), but also because replacing or retrofitting them is usually prohibitively expensive (tearing up roads, installing bridges or larger culverts, etc). Nevertheless, I'm glad to see some effort is finally being made to recognize the problem. Every little bit helps.]
The program is also limited by geography. Although the only culverts eligible for funding are those that obstruct sea-run fish, many landlocked species also migrate. In the Great Lakes region alone, perhaps 250,000 culverts confound suckers, pike, brook trout, and other freshwater denizens. These fish won’t benefit from federal largesse, yet they need help as surely as any coho or chum.
by Ben Goldfarb, Hakai Magazine | Read more:
Image: Maggie Chiang
[ed. In Alaska, culverts were a major headache. We had staff at the Alaska Dept. of Fish and Game who spent years assessing impacts on fish populations, trying to find solutions (scientifically, politically, economically) to mitigate the damage they cause. Here are a few examples of their effects: creating impenetrable barriers to fish passage when debris gets washed downstream and lodged at their openings; becoming perched several feet above streams due to discharge scouring from flood events (or initial bad engineering); designed too narrow so that water velocities exceed the swimming capabilities of young fish (fire hose example); and frequently becoming magnets for predators (including humans) who find pooled fish in a single location easy pickings. Migrating salmon are famous for their spawning imperative and endurance - I did a fish survey in Anchorage one time that found coho salmon fry upstream of a culvert that stretched half way across the city under numerous roads, business parks and subdivisions - over a quarter mile long. But, only a handful of fish could have survived that gauntlet, and I didn't find many fry in that sample. This is a massive problem, not only because there are so many culverts in fish streams (in various stages of disrepair), but also because replacing or retrofitting them is usually prohibitively expensive (tearing up roads, installing bridges or larger culverts, etc). Nevertheless, I'm glad to see some effort is finally being made to recognize the problem. Every little bit helps.]
