Geomorphic Based Grade Control

Little Browns Creek Geomorphic-Based Grade Control

Location: Trinity County California
Clients and Partners: Trinity County and The 5 Counties Salmonid Conservation Program

Michael Love & Associates (MLA) designed and provided construction guidance for a 300-foot reach of channel in 2007. This oversteepened channel reach was part of a crossing replacement where a culvert served as a knick-point in a dramatically incised channel.

The constructed channel has a slope of 5 percent to overcome 15 feet of drop.  The channel was designed and constructed with a series of chutes, steps and small pools to provide fish passage for adult and juvenile steelhead trout and coho salmon.  Large wood structures were added during construction to scour pools and provide cover for fish. Bioengineering bank stabilization with willow mattresses was used along channel banks to reduce the amount of bank rock required to stabilize the new channel.

MLA’s design included developing a new channel profile and cross section, preparing an engineered streambed material gradation that would be stable up to the 100-year discharge, and evaluating shear stresses on the banks and bed.

Post project biological monitoring has shown that the project provides fish passage. Spawning adult steelhead were identified upstream of the channel reach and juvenile fish were found utilizing the pools within the project reach.