Two summers ago the Lower Columbia Estuary Partnership and Collins
oversaw the rebuilding of a slough that 50 years earlier had been
virtually cut off from the Columbia by the construction of Interstate
84.
As state and federal agencies look for ways to rebuild runs
of endangered Columbia River salmon and steelhead, they turn to
Portland-based nonprofit groups like the Columbia Partnership, which
specializes in finding and restoring wetlands. Habitat restoration in
the Columbia basin is one of four areas of emphasis to rebuilding salmon
runs.
The U.S. Environmental Protection Agencies and the states
of Oregon and Washington created the Lower Columbia Estuary Partnership
20 years ago to tackle habitat projects along the 140 miles of river
from Bonneville Dam to Astoria. Although it gets private contributions
or state and local help for projects, the bulk of its funding comes from
the Bonneville Power Administration as mitigation for environmental
harm caused by Columbia River dams.
Which led LCEP and Collins to Horsetail and Oneonta creeks back in 2010.
The
two creeks feed the 190-acre wetland tucked between the gorge’s steep
basalt cliffs and I-84. But when engineers built the freeway they cut
off four outlets to the Columbia and channeled all the water through one
massive 230-foot long culvert.
In the spring, juvenile fish
heading downstream like to use wetlands to rest, escape predators and
grow. In the summer and fall, adult fish returning upstream use sloughs
to cool off until temperatures drop in the Columbia.
Because of
the culvert’s design the Oneonta/Horsetail wetland was barely accessible
to migrating fish. If fish made it past the culvert they found the
floodplain inhospitable — long straight channels without good shelter
that got too warm in the summer. A three-acre pond fed by Oneonta Creek
in the winter would get cut off from flows once the stream receded in
the summer.
The U.S. Forest Service owns the land and identified
the area as a good one to restore. It contacted LCEP and in 2010 the two
began collecting data on water flow and temperature, fish and plants.
In
2013 crews used a two-month summer construction window to carve twists
and turns into straight channels, place logs and root balls for shelter,
shrink and make the pond better for fish, and plant thousands of trees
and native plants to provide shade.
Now two years into four years of post-construction monitoring, Collins and LCEP are pleased with what they are finding.
Changes
to the culvert have improved passage, water temperatures have dropped
significantly, and logs, root balls and plantings have taken hold.
“We’re
very happy with passage and temperature results,” says Collins, LCEP’s
principal restoration ecologist. “These sites are dynamic so it’s always
interesting to see how they evolve.”
In the culvert, 18-inch
high baffles were notched to 6 inches so juvenile fish in the spring and
summer and adult fish in the fall can more easily reach the creeks. A
wide, flat concrete slab that funneled water into four of the culvert’s
five tunnels was replaced with gravel and rocks to aid fish travel into
the slough.
An
array of electronic monitors at both ends of the culvert now tells
researchers when specially tagged fish move in or out of the wetlands.
“We get lots of hits of juveniles tucking into the site,” says Collins. “We’re seeing them in the summer and fall.”
