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[ Fish Passage Improvement ] [ Streambank Stabilization ] [ Invasive Species Removal ] [ Trail Improvement ]
The
Mat-Su
Basin
supports an incredibly rich fisheries resource. Every summer, hundreds of
thousands of salmon return to their natal streams to spawn. This basin
also supports the fastest growing human population in
Alaska. More people means a need for more
homes and more roads. Each time a
road passes over a creek, either a bridge must be built or a culvert installed.
In most cases, culverts are a more cost-effective and sensible option. The Mat-Su Borough currently has almost 300 official culverts in place,
while numerous private culverts exist on private property as well. During high water or flood events, culverts are sometimes not large
enough to adequately handle the amount of water flowing through the system.
As a result of water being forced through a relatively narrow passage,
flow rate increases and water scours the creekbed on the downstream end
of the culvert. When the water
returns to more normal levels, the culvert becomes “perched” above the water
level of the scoured-out creek. Although
adult salmon may be able to make the jump required to get through the culvert,
perched culverts are essentially a wall for juveniles and fry. Valuable upstream habitat from these perched culverts is therefore
completely closed off to rearing salmon.
We have been successful in efforts to improve fish passage through such perched culverts.
Our tactic has been to build “step pools” downstream from perched
culverts to essentially raise the water level until the culvert is no longer
“perched.” Though not a
permanent solution to the problem, step pool construction can help improve fish
passage temporarily until undersized culverts can be replaced by larger ones.
(click to enlarge photos; then use the back arrow to return to this
page)
By teaming up with 5th
graders at Knik Goose
Bay
Elementary School
to construct step pools in Crocker Creek and the Alaska State Forestry Interns
to construct step pools in an unnamed tributary of the Little Su, we took
advantage of great opportunities to involve students in tangible projects in
which they could see the positive difference they had made in just one day!
And with so many eager bodies willing to work, we were able to keep costs down
and tread lightly around the creek without a need for heavy equipment.
Knik
Goose
Bay
Elementary School
students...busy
beavers building check dams:
(click to enlarge photos; then use the back arrow to return to this
page)
Alaska
State
Forestry Intern Crew...any future stream restoration ecologists!?:
(click to enlarge photos; then use the back arrow to return to this
page)
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