Sub-Reach 3 Completion, Lower Lemhi Rehabilitation Project P2

Salmonid Habitat Restoration and Acquisition

Instream Habitat Riparian Habitat
Project ID018 18 SA
Recovery DomainsInterior Columbia
Start Date11/28/2018
End Date12/31/2019
Year2018
StatusCompleted
Last Edited10/21/2021
 
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Description    


The Lower Lemhi River Rehabilitation Sub-reach 3 (SR3) project is one of 4 sub-reaches within a 2.5 mile contiguous river segment that the Idaho Department of Fish and Game (IDFG) is implementing to restore fish habitat. This contract supported ongoing efforts by IDFG to complete final construction actions for SR3. Most of the project actions were completed under previous contracts. However, challenges with finding sufficient large trees and other woody material at a reasonable cost, a higher than expected “low bid” that was accepted and awarded to a contractor, and an underestimation of the amount of material needing to be excavated to create floodplains resulted in a significant shortage in funding.

Project Actions. The remaining project actions that needed to be completed include construction of the last lateral side channel and floodplain complex, installation of engineered log jams, shaping of the floodplain to blend with existing pasture, connection with the mainstem river, installation of an irrigation water siphon, and installation of cattle exclusion fencing. Construction for these actions commenced in early 2019. Excavation began on the upper end of the SCC 1 floodplain complex in late January (Figures 1 and 2). Prior to excavation, the top organic layer consisting of topsoil and sod was stripped and placed on the edges of the channel complexes. Channel alignments were then excavated per design. Multiple side channels that braided through a floodplain swale and inset benches were excavated, and river banks were shaped to promote flooding. IDFG secured additional woody debris for the remaining engineered log jam treatments (Figure 3). Four different types of engineered log jams were constructed within SCC 1 (Figures 4 and 5); 1) Type 1 engineered log jams promoted vertical scour to create a large pool while maintaining a channel split, 2) bleeder log jams directed flow as prescribed to maintain a primary channel while providing in channel complexity, 3) bank log jams created pools and provided large woody debris, and 4) bank roughening complexes provided bank stability and high complex lateral fish habitat. In addition, large loose trees containing rootwads were strategically placed in the channels to provide additional roughness and fish habitat (Figure 5).

Since a large portion of the project utilized existing pasture and directly affected irrigation canals and water delivery, some mitigation was necessary to allow the ranch to irrigation other areas previously irrigated. Thus, a siphon used to convey irrigation water under one of the constructed channels was installed.

Establishment of a functional riparian area was one of several objectives we established to meet the project goal. Thus, conditions sufficient to successfully grow and support riparian vegetation were important for completing this objective. We completed final floodplain grading in the associated disturbed areas, and topsoil containing sod clumps previously salvaged was placed throughout floodplain areas, inset benches, and along channel banks. Willow trenches were installed, were 20 – 30 willow cuttings were placed in a 5 ft deep trench and backfilled with topsoil. Additional willow stakes were randomly planted throughout the floodplain complex. A native seed mixture was applied to all disturbed areas, and IDFG irrigated these areas in the summer to promote germination and growth (Figure 6). As stated previously, additional wood debris and other organic material was also placed to further promote vegetation growth (Figure 5). These actions have ultimately expanded the active floodplain significantly over previous conditions.

All floodplain complexes were activated once channel construction was completed.


Project Benefit    


The purpose of this project is to improve freshwater productivity of the Lemhi Spring/Summer Chinook salmon major population group and the Snake River Lemhi Steelhead distinct population segment, both of which are currently listed as threatened under the ESA. This reach does not effectively support most life stages of salmon and steelhead. It lacks proper stream channel structure and function, instream structural complexity, and proper bed and channel form. Sediment quantity is poor, in that, large homogenous substrate unsuitable for salmonid spawning dominates the reach. Water velocities are very high, and there are no slow water or lateral habitats suitable for fish rearing and growth. There is a substantial loss of riparian vegetation, and the existing condition is poor. Stream temperatures are elevated during summer periods, in part due to loss of riparian vegetation within and upstream of the proposed reach. Project actions will improve all of these identified issues.

Accomplishments

Metric Completed Originally
Proposed
Instream Habitat
  Stream Miles Treated .30 .30
Riparian Habitat
  Stream Miles Treated .20 .19
  Acres Treated 2.0 2.0

Funding Details

SourceFunds
PCSRF$495,495
Other$167,341
Report Total:$662,836


Project Map



Worksites

SR3, P2 Lemhi River    


  • Worksite Identifier: SR3, P2 Lemhi River
  • Start Date: 04/01/2019
  • End Date: 12/01/2019
Area Description
Lemhi River

Location Information

  • Basin: Salmon
  • Subbasin:
  • Watershed:
  • Subwatershed:
  • State: Idaho
  • Recovery Domain: Interior Columbia
  • Latitude: 45.114758
  • Longitude: -113.764481

ESU

  • Snake River Spring/Summer-run Chinook Salmon ESU
  • Snake River Basin Steelhead DPS

Map

Photos

Metrics

Metrics
  • C.0 Salmonid Habitat Restoration and AcquisitionY (Y/N)
    •      . . C.0.a Habitat restoration and acquisition funding 662,836.00
    •      . . C.0.b Length of stream treated/protected .30
    •      . . C.0.c
      Project identified in a Plan or Watershed Assessment
    •      . . C.0.d.1 Project Monitoring (LOV)
    •      . . C.0.d.2 Monitoring Location (LOV)
    •      . . C.4 Instream Habitat ProjectY (Y/N)
      •      . . . . C.4.a Instream Habitat Funding 632,336.00
      •      . . . . C.4.b Total length of instream habitat treated .30
      •      . . . . C.4.c.1 Channel reconfiguration and connectivityY (Y/N)
        •      . . . . . . C.4.c.2 Type of change to channel configuration and connectivity (LOV)
        •      . . . . . . C.4.c.3 Miles of stream treated for channel reconfiguration and connectivity .30
        •      . . . . . . C.4.c.4 Miles of off-channel stream created through channel reconfiguration and connectivity .12
        •      . . . . . . C.4.c.5 Acres of off-channel or floodplain connected through channel reconfiguration and connectivity .4
        •      . . . . . . C.4.c.6 Instream pools created/added through channel reconfiguration and connectivity 0
      •      . . . . C.4.d.1 Channel structure placementY (Y/N)
        •      . . . . . . C.4.d.2 Material used for channel structure (LOV)
        •      . . . . . . C.4.d.3 Miles of stream treated through channel structure placement .30
        •      . . . . . . C.4.d.4 Acres of streambed treated through channel structure placement 2.5
        •      . . . . . . C.4.d.5 Pools expected to be created through channel structure placement 3
        •      . . . . . . C.4.d.6 Yards of average stream-width at mid-point of channel structure placement project30 (Yards)
        •      . . . . . . C.4.d.7 Number of structures placed in channel 12
      •      . . . . C.4.e.1 Streambank stabilization Y (Y/N)
        •      . . . . . . C.4.e.2 Material Used For Streambank Stabilization (LOV)
        •      . . . . . . C.4.e.3 Miles of streambank stabilized .02
      •      . . C.5 Riparian Habitat ProjectY (Y/N)
        •      . . . . C.5.a Riparian Habitat Funding 30,500.00
        •      . . . . C.5.b.1 Total riparian miles streambank treated .20
        •      . . . . C.5.b.2 Total Riparian Acres Treated 2.0
        •      . . . . C.5.c.1 Riparian plantingY (Y/N)
          •      . . . . . . C.5.c.2
            Species of plants planted in riparian
            Salix spp.
          •      . . . . . . C.5.c.3 Acres planted in riparian 2.0
          •      . . . . . . C.5.c.4 Miles of streambank treated with riparian planting .15
        •      . . . . C.5.d.1 FencingY (Y/N)
          •      . . . . . . C.5.d.2 Miles of fence along stream .15
          •      . . . . . . C.5.d.3 Acres of riparian area protected by fencing .3
        •      . . . . C.5.f.1 Water gap developmentY (Y/N)
          •      . . . . . . C.5.f.2 Number of water gap installations 1
          •      . . . . . . C.5.f.3 Miles of streambank protected by water gap development .01