Urban streams in sad shape, report finds
Urban creeks will never look or function like their more pristine country cousins. But that doesn't mean they have to be dead zones, a freshwater ecologist points out.
Seattle Times staff reporter
Learn moreThe report Read the full report, learn how to get a habitat-improvement grant for your neighborhood, and find out what you can do to improve your neighborhood creeks:
Source: Seattle Public Utilities
• Impervious surface covers 59 percent of the watershed, substantially increasing stormwater runoff and stream flows that damage stream habitat.
• There are 10.8 stormwater outfalls per every stream mile.
• The stream is polluted with fecal coliform, traced to pet and wildlife waste.
• Low levels of pesticides are found in stormwater and sediment samples.
• Environmental degradation of the creek is taking a toll on living creatures. The stream has a very low diversity of invertebrates, a link in the food chain. A very high percentage of adult coho — 79 percent on average — die before they can spawn when they enter the creek. The stream also has 25 complete barriers to fish passage.
• The stream in many places has been armored, straightened, and confined — which destroys habitat. In many places, the banks consist of lawns, landscaping and invasive plants instead of high-quality native habitat.
• Restoration efforts show promise: fish habitat has improved; local flooding has been reduced in some areas.
The doctors have taken a close look, and the results aren't pretty: In too many places, Seattle's five urban streams are in poor shape.
After years of research, Seattle Public Utilities today released its State of the Waters Report, the agency's first comprehensive scientific assessment of Seattle's five major creeks: Fauntleroy, Longfellow, Taylor, Thornton and Piper's. The results are intended to provide a readily accessible reference of current conditions, which policymakers and citizens can use to guide restoration efforts.
"This is about how do we come up with realistic expectations: Scientifically, what is the foundation upon which we can build a plan for restoring the health of our watersheds?" said Julie Hall, who led the project for SPU.
"We are never going to get back to 100 years ago. Today these places are supporting a lot of residences and transportation uses and jobs. What we learned is the land and water are completely connected, and what happens on the land plays a large role in what happens in the water."
Among the report's key findings:
• Armoring stream banks with concrete and rocks, paving the uplands, filling wetlands, and crowding floodplains with buildings, roads and other development all have degraded the stream habitats.
• The damage done by 150 years of development is extensive. Today as much as 60 percent of the land in some Seattle watersheds is paved. Migratory fish, including salmon, are blocked from reaching about 70 percent of their potential habitat, including some of the best remaining areas in the city where fish could thrive.
• Flows in Seattle's streams are flashy, ramping up and down with bursts of stormwater runoff. That destroys fish habitat and can result in flooding that damages homes and property. Even in moderate storms, such as heavy downpours that come at least every two years, stream flows explode to about four to five times what they would have experienced in the days when trees, instead of pavement, covered the landscape.
• Most creeks don't meet state water-quality standards for temperature or cleanliness. With some exceptions, the limited available information shows the biggest pollutants aren't chemical toxins or leaky sewer pipes — it's pet and wildlife waste.
• Living creatures are paying a heavy price for our abuse. In some watersheds, such as Thornton Creek, about 79 percent of adult coho die before they can spawn. Salmon returns in some reaches numbered fewer than 10, and the diversity of invertebrate life in the stream bottoms — a key element in the food chain — is greatly reduced.
• Accurately assessing the state of the city's streams was difficult because of limited data, particularly with regard to water quality and flow. The city badly needs a monitoring program to track the status and trends of stream health.
In discussing the findings, scientists who worked on the report said it shouldn't be read as an autopsy. Urban creeks still offer an important chance for city residents to connect with the natural world around them, they said. And they can be improved.
On a winter afternoon this month, Carl Menconi, who lives along Thornton Creek in the Meadowbrook neighborhood, watched the stream sluice under one of several bridges installed by the city in a restoration program to replace the culverts that used to clog and back up during storms, threatening homes with floodwater.
The city also brought in an excavator to claw out the blackberries and move the stream banks back a bit, to give the creek room to flood. Woody debris and rocks installed in the creek bottom provided places for fish to rest and hide.
Not long after the project was completed, Menconi said, he spotted a coho nesting in the creek bottom. And during this month's heavy rains, the creek flooded in some parts of the neighborhood, including at Nathan Hale High School, but not in the parts where the restorations had been done.
In a neighborhood where winter storms had become synonymous with sump pumps, "it took some adjusting to the idea that things could be better," Menconi said.
But this time, when high water came, the broader, more natural channel created by the restoration work helped tame flows and keep the water in the stream, where it belongs.
"What's good for fish is also good for people," said Chris May, a freshwater ecologist with SPU.
Urban creeks will never look or function like their more pristine relations in rural areas. But that doesn't mean they have to be dead zones, either, May said.
"A livable city goes right along with an ecosystem that works."
Lynda V. Mapes: 206-464-2736
Copyright © 2007 The Seattle Times Company
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