This is part of a multiphase project that addresses long-term, systemic problems associated with bedrock-dominated habitat conditions in a river-sized stream including: a lack of accumulated gravels, lowed late season flow levels, temperature impairment, channelization, and loss of connectivity between primary and secondary channels.
SOLUTION
This Phase II project constructed five, channel-spanning boulder weirs numerous boulder clusters, and a few rock barbs were installed in the stream channel to improve aquatic habitat conditions in 1.44 mi of mainstem Mosby Creek. The Mosby Creek Phase II project involved the placement of over 800 structural pieces to create
habitat for fish. The lower site saw the construction of three channel-spanning weirs in succession, resulting in a contiguous area of influence of over one stream mile. The upper site hosted two additional weirs in order to connect a series of four weirs in addition to a floodplain area.
RESULT
In-stream boulder placement will provide structure and habitat in the main stream channel . Placement of rocks will sort and accumulate spawning gravels that should make spawning habitat available for spring Chinook salmon. In addition, placement of boulders will provide places for fish to take refuge, and, we hypothesize, lower temperatures in the end by enhancing the hyporheic zone under this accumulated gravel. Localized scour will create pools, and therefore more instream habitat diversity. This project is anticipated to have a direct impact on two stream miles of aquatic habitat. Our project came full circle when in 2014 we witnessed our first fish spawning in the Row River and in the spring of 2015 had our first run of fishable spring Chinook salmon return to the watershed in over 40 years.
