Rock Creek, the main tributary to the
lower North Fork of the Blackfoot River, is formed by the confluence of Salmon Creek and
Dry Creek on the northeastern edge of Kleinschmidt Flat. This stream flows 8.2 miles
in a south-westerly direction, joining the North Fork at river mile 6.2. Its flow
measured 53 cfs on July 24, 1989. Kleinschmidt Creek joins Rock Creek immediately upstream
of the North Fork junction. Rock Creek occupies a channel historically formed by a
braided glacial outwash stream. Upper Rock Creek skirts the foothills on eastern edge
of Kleinschmidt Flat before entering the flat where it loses water to alluvium and
irrigation. In the lower portion of Kleinschmidt Flat, groundwater surfaces, forming
the spring creek portion of Rock Creek.
Habitat surveys completed in the lower
8.2 miles indicate the condition of the stream and riparian areas as severally degraded,
being extremely wide and shallow. Livestock had sheared wet banks, logging has impacted
the stream channel, irrigation has dewatered the stream, culverts have blocked fish
passage, and tillage of the riparian areas have contributed to the poor condition of the
stream. A representative cross section profile of the channel at mile 3.7 had a base
flow wetted width of 35 feet and a maximum depth of 6 inches. According to our
measurements, normal bankfull channel width and depth for this channel type (E5) are 8
feet and 18 inches, respectively. 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. Rock
Creek is ranked 7 of 83 streams surveyed.
Restoration activities began in the
lower 1.2 miles of Rock Creek in 1990. Eight barriers to fish passage (culverts, dams
and diversions) were removed and more efficient diversion structures were created at two
headgates. Conversion from flood to sprinkler irrigation was made, improving water
management and conservation, and allowing increased stream flows in the channel. Over
three miles of instream habitat was restored to its historic E4 channel type. Adding
woody debris to the stream, planting riparian shrubs and conifers, and grazing management
have been implemented on over 5 miles of Rock Creek.
Aerial view of the Rock Creek restoration.