Introduction

The purpose of this project is to improve fish habitat, reduce erosion and improve water quality in the Lower Imnaha River.  The GRMW is proposing to stop 340 feet of severe bank erosion on the Imnaha River on property owned by the Marr Family Trust.  Several methods will be utilized including the installation of an engineered log jam, one woody habitat feature, 3 woody debris structures, approximately 300 feet of bank stabilizing toe logs with rock ballast, native vegetation planting and livestock exclusion fence.  Project results will be improved backwater and off of main river channel habitat, habitat complexity, water quality and riparian vegetation conditions.  Construction is scheduled for the late summer and fall of 2011.  Partners include GRMW (sponsor), Anderson Perry & Associates (design and engineering), Marr Family Trust (landowner), and ODFW (technical assistance).   This project compliments other restoration efforts in the Imnaha Subbasin.  Livestock management, riparian planting, erosion control, habitat complexity improvement and weed control are all efforts ongoing in the area that this project will compliment.  

Existing condition

The primary land use at the project site is livestock management including winter feeding operation and grazing.  Riparian vegetation consists of annual grasses and herbaceous species with shrub and overstory vegetation absent.  The absence of bank stabilizing shrub and overstory vegetation has lead to an unstable streambank and subsequent erosion.  Over the past 10 years 100 lateral feet of the riverbank has eroded threatening to wash out the access road to neighboring property downstream.  With the cooperation of the Marr Family Trust, this project provides the opportunity to improve fish habitat, riparian and water quality condition while protecting property and road infrastructure.

Project Objective/Specific Actions:

*  Install large woody material in Imnaha River Channel:  Reduce erosion on the Marr property and sediment contribution to the Imnaha River to improve habitat conditions for aquatic species.

*  Increase available fish habitat in the Imnaha River by constructing habitat features that will improve habitat complexity and diversity.

*  Stop Imnaha River channel widening on the Marr property to maintain or improve existing channel width to depth ratio.

*   Install Fence/Plant Vegetation:  Improve riparian vegetation condition on the Marr property adjacent to the Imnaha River by planting riparian vegetation and installing livestock exclusion
fence in the project area.

Construction work will be between August 1st and October 15th, 2011 corresponding with the ODFW in-water work window.  Fencing and planting can occur out of this time frame, as this is not in-water work.  Planting will likely occur in November corresponding with plant dormancy and prior to the ground freezing.  Fencing can be done at any time from project start to finish.  This project will be complete by November 30, 2011.  We are requesting a BPA contract term of July 1, 2011 to January 31, 2012.  

Benefits

Reduced erosion:  Bank stabilizing activities are expected to eliminate eroding banks in the project area.  This will reduce sedimentation and improve water quality in the Imnaha River.  Bank stabilizing will eliminate the widening of the Imnaha River channel.  This will preserve or improve existing width to depth ratios.  

Improved aquatic habitat conditions:  Habitat conditions will be improved through the installation of the woody debris structure, woody habitat structure and the engineered logjam.  These structures will provide habitat complexity, hiding cover and resting habitat during periods of high flow condition in the project reach.

Restored Riparian Community:  An aggressive native species planting plan combined with fencing and livestock exclusion will act to restore the riparian area in the project reach.  Results will not be immediate but the 10-year period of non-use will promote a recovery of the riparian community.