|Dunham Creek, a second-order tributary
flows 13 miles through an alluviated glacial valley, joining Monture Creek at stream mile
11.5. Stream discharge was measured at 32 cfs on July 15, 1996. The channel is
composed of laterally moving sand, gravel and cobble substrate, with a riffle/pool habitat
sequence in the mid to lower reaches. Portions of the stream are unstable with both
aggraded and incised reaches. In order to prioritize restoration resources, we developed a
fisheries-based restoration priority scorecard, based on biological, social and financial
considerations, for 83 impaired tributaries of the Blackfoot River. Dunham Creek ranked 11
of 83 streams surveyed.
Stream mile 4.2 (Photo taken in 1974)
Stream mile 2.2
The poor condition of the Dunham Creek fishery is a result of altered and unstable stream
channels caused by poor riparian timber harvest practices and subsequent channelization (Photo #1) which may cause the stream to go sub-surface during
base flows; and entrainment of native fish into an irrigation canal (Photo #2). In 1995, the loss of westslope cutthroat trout,
juvenile bull trout, and a spawned, radio-tagged bull trout to this canal were documented.
Self-cleaning paddle wheel fish screen.
fall of 1996, the canal was fitted with 19 cfs self-cleaning paddle wheel fish
screen. In 1998, 10 bull trout redds were located in Dunham Creek above the fish
screen. The graph above shows densities of bull and cutthroat trout (Fish >
4.0") before and after screening the irrigation ditch.
Stream mile 2.3 is just above the irrigation
ditch and just below the bull trout spawning site. This
section of the stream was not logged or channelized and is in excellent condition. Stream
mile 4.2 is the logged and channelized reach shown above in Photo #1.
Stream mile 2.3
|In 2000, we completed the
reconstruction of 1.3 miles of Dunham Creek to natural channel dimensions consistent with
a stable alluviated (C4-type) channel. Before the project, mean bankfull width in the
degraded project reach was 62.2 feet compared to mean stable reference reach bankfull
width of 37.1 feet. The width/depth ratio of the reference reach was 22.4 compared to 59.1
in the project reach. Sediment deliveries in the project area were 25 times the natural
levels. This influx of unnaturally high levels of sediment entered the channel immediately
upstream of the Dunham Creek bull trout spawning area.
The restoration project focused on channel
reconstruction with emphasis on natural channel morphology, habitat complexity and
included an aggressive revegetation of disturbed banks. The primary objective of the
project was to stabilize the stream to allow riparian vegetation to encompass the stream
over a 10-15 year period and thus provide long-term stability.
We resurveyed fish populations at two monitoring
sites (mile 2, 3 and 4.2) in Dunham Creek before channel reconstruction. Both sample sites
show lower native fish densities in 2001 compared to earlier surveys. These recent
population declines likely result from low flows (related to drought) and a large influx
of fine sediment (primarily sand) in spawning riffles downstream of the channelized reach.
Post-project monitoring will be conducted to assess the effectiveness of this restoration
Spawning bull trout
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