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Critter Crossings: Linking Habitats and Reducing Roadkill

Programs to Remove Fish Passage Barriers


[Photos of a creek - These pictures show McDonald Creek before (above) and after (below) fish passage barriers were removed.]

Wild salmon and sea-run trout need upstream habitat for spawning. Getting there is the challenge.

In many Washington streams, wild salmonids get part way into an upstream culvert, only to be washed back downstream. If they do make it upstream, they're often too exhausted to spawn. If they don't make it and have to spawn in densely-populated downstream areas, their offspring are often forced to compete for any available rearing habitat.

Washington's wild salmon and trout are getting a break, thanks to an ambitious program to remove fish passage barriers along state highways. In this ongoing, state legislature-funded program, teams from the Washington State Department of Transportation and the Washington Department of Fish and Wildlife are working together to identify, prioritize, and remove barriers in culverts under state roads. Since the program began in 1991, they've surveyed tens of thousands of road crossings to come up with 4,463 sites where state highways cross fish-bearing streams. They've identified more than 500 "problem culverts" at these sites - culverts where the water depth is too shallow, the water velocity too high, or the outfall drop too far. Engineers have begun fixing the culvert barriers using a "Priority Index System" that ranks projects according to their potential habitat gains.

[Photo of Rasmussen Creek culvert before before removal - For years, fish could not swim through the fast-moving waters in these Rasmussen Creek culverts (above). Replacing the culverts with a single archway solved the problem (below). - Photo of Rasmussen Creek single archway.]

Here are two of the program's success stories:

Rasmussen Creek (Clallam County) - Two round culverts under State Route 112 had been built on a steep slope, so the water velocity was too high for most fish swimming upstream. Engineers replaced the culverts with a single concrete archway spanning the stream - ideal "natural" conditions for fish passage. The project added nearly 7/8ths of a mile (1,324 m) of stream habitat, and post-project surveys reported coho salmon, cutthroat trout, and other fish species in the upstream section of the creek where they had not been seen before.

McDonald Creek (Mason County) - Not even one fish could enter this upstream box culvert under State Route 108, because the culvert was perched 6 feet (1.8 m) above the streambed. Engineers installed a pool-and-weir fishway (a concrete "flume" dotted with weirs). Each pool is slightly higher than the pool below, allowing fish a gradual climb to the culvert. The project increased stream habitat by 1,393 yards (1,279 m). A December 1998 survey counted 475 chum salmon, and a survey taken only one month later, 908 chum.

The Washington State Legislature is so confident of the success of the interagency program to remove fish passage barriers, it has pledged to support the program for a 20-year period and has increased its funding from an initial $2 million/biennium to $4 million/biennium to $9.3 million for 1999-2001.

For more information, contact Cliff Hall, 360-705-7499 or


[Photo: Canyon Creek - Occasional floating debris won't clog these plastic baffles on Canyon Creek, because the baffles have a 45-degree slant.]

In the early 1960s, highway engineers realigned fast-moving Canyon Creek in Douglas County to make room for improvements to Interstate 5. To stabilize the new slopes and stream bottom at certain locations, they covered the sides and bottom of the creek with concrete.

The change was bad news for Oregon's wild salmon and trout.

At Milepost 94.2, where the water velocity was frequently 15 feet (4.6 m) per second and the water depth a scant few inches, only a few steelhead trout were able to make it upstream. The steep terrain, narrow culvert, and concrete-covered sides and bottom precluded using traditional methods to fix the problem.

Teams from the Oregon Department of Transportation (ODOT) and the Oregon Department of Fish and Wildlife, who had been working together to remove fish passage barriers, came up with a "natural" solution. They used fishrocks to slow the velocity in the steepened streambed and to create small fish resting areas. The technique involved placing large rocks in a form of wet concrete secured to the existing concrete streambed and culvert bottom.

Water depth increased from 4 to 6 inches (10 to 15 cm) to about 11/2 feet (0.5 m) - deep enough for steelhead, Chinook, and other wild salmon and trout to rest in while making their way upstream. Water velocity in these resting areas slowed to 1 to 2 feet (0.3 to 0.6 m) per second. "There is still some fast-moving water between the resting pools," says ODOT hydraulics engineer Lance Clark, "but since the pools are only one meter apart, the fish can skirt through the swifter water and hide in the resting areas."

At other stream-road locations, ODOT teams used different techniques to remove fish passage barriers. For example, at Milepost 95.39, they used a plastic baffle to slow water velocity and increase water depth through the culvert. The award-winning device, invented by Clark, works like a concrete or steel baffle. Clark's version is lighter, cheaper, and won't corrode. It's also designed with a 45-degree slant so any floating debris can easily pass over it.

At Cleveland Creek 4 miles east of Mapleton on Highway 36, the teams used a series of rock weirs (upstream-pointed, "chevron" shaped networks of rocks) to pool water. "The weirs let fish swim - not jump - into the culvert outlet," says Clark. "This is a particular advantage for juveniles, who can't jump very high."

[Photo: Cleveleand Creek - Thanks to the upstream-pointed rock weirs at this location on Cleveland Creek, fish have an easier time swimming into the culvert.]

In fewer than 25 weeks over the past three summers, ODOT has removed 55 fish passage barriers at stream-road culverts, opening up more than 100 miles (161 km) of habitat. Many more barriers need to be removed, according to state surveys, but ODFW Fish Passage Coordinator Albert Mirati thinks ODOT is equal to the task. "All levels of transportation are now stressing fish passage," he says. "They even go out and fix barriers on their own volition."

For more information, contact Lance Clark at 503-986-4346 or

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Updated: 7/18/2012
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