Seattle Press on Line - How to Rebuild Fish Habitat in Urban Creeks

How to Rebuild Fish Habitat in Urban Creeks

Jeff Bouma and Christina Avolio are interns in Seattle Public Utilities’ Habitat survey.

Tips for people who live near creeks

* Keep water cool; plant native species along the bank. Don't try to have a lawn running right up to the stream edge.

* Use less fertilizer on your lawn. Much of it washes right into the creek.

* Good creek bank plants: red twig dogwood, sword fern, red cedar, salmon berry, thimbleberry.

* Don't pull out fallen logs and branches. These provide fish habitat and shelter from storm runoff and predators.

By Tom Herriman

Sep 06, 2000 -- Seattle Public Utilities (SPU) is conducting a habitat survey of several city creeks to determine where good fish habitat exists and what needs to be done to preserve and expand it. Catherine Lynch, Senior Environmental Analyst and Urban Creek Biologist for SPU, said the survey of Thornton, Carkeek, Longfellow and Fauntleroy creeks will cover geology and hydrology as well as habitat. The study will help SPU decide "where to do restoration, or to try to acquire land; where the best and where the most threatened habitat is," Lynch explained.

She said the presence of large numbers of cutthroat trout in Thornton Creek proves that the creek can support fish. But only a handful of coho smolts showed up in a recent fish census. "They might have been introduced by school groups," Lynch said, "rather than through natural spawning. That's one of the things we're trying to figure out."

The Seattle Press recently accompanied two hip-booted, clipboard-armed SPU interns on a walk along Thornton Creek near the intersection of 10th Avenue Northeast and Northeast 125th Street.

Jeff Bouma, a recent graduate of the University of Washington Landscape Architecture program, explained, "We're looking for habitat units...ripples and glides in the stream with gravel bottoms or dead wood in the water, shaded by overhanging boughs, places where the water slows."

He said fish need these quiet areas in a stream for spawning, hiding from predators and avoiding the devastating effects of storm runoff.

In a natural environment, rain seeps through the ground, which acts like a giant sponge that absorbs and releases water gradually. But urban streams get blasted by huge changes in water flow. "It's up and down up and down," Bouma said, "and the result is severe erosion, scouring and lots of unhealthy debris in the water."

The volume of water in Thornton Creek can quadruple within a couple of hours when run-off from streets, roofs and parking lots courses through storm drains which dump directly into the creek. Cigarette butts, fast food wrappers, leaking oil and antifreeze from cars--whatever people put in the street will end up in the creek. The resulting flood is devasting for fish, who can get swept down into the lake or the sound. Habitats are eroded or wiped out. The solution, Bouma said, is to make sure there are turn-outs, quiet dead end channels, and pools created by fallen trees and limbs.

Chinook salmon, rainbow trout and stickleback are found in Thornton and some of the other creeks in the study including Longfellow, Piper's and Fauntleroy. There is a chum salmon run in Piper's Creek, which flows through Carkeek Park in Northwest Seattle, and a coho run in Fauntleroy Creek in West Seattle.

Throughout the creek, herds of crawdads scurried across the bottom.

Herons feed in the creek on a regular basis and hawks perch in trees along the banks. As I followed the survey crew in from 10th Avenue, the vegetation grew thick along the banks and the sunlight filtered through the trees making a filigree pattern on the water.

The arching overgrowth helps keep the water cool, according to Christina Avolio, a Seattle University student in environmental engineering.

Parts of the creek are on city land, and parts of it flow across private property.

"We ask property owners not to try to have a lawn right up to the water's edge. It's best for the fish if there are overhanging bushes and shrubs and trees along the bank," she said.

Bouma said some stream cleanup efforts in the past have made things worse. "Don't pull out the logs and fallen tree branches. The fish need those and the creek is healthier with the complexity provided by natural debris in the water.

"Complexity creates the pool," Bouma said, standing in a quiet area of the stream in about 1 1/2 feet of water. There was a canopy of alder and cottonwood where he was standing, and ferns and berry bushes drooping over the bank. It was quiet except for the rippling of the water and the buzzing of insects. It seemed like a good place for a fish to live.

Thanks to Skip Knox for his news tip.

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