Northwest Hydraulic Consultants (NHS)

Fish Passage and Fisheries Engineering Services


Designing new hydraulic structures and modifying existing structures to ensure passage for fish and other aquatic organisms is an important tool for restoring ecological conditions and recovering endangered species. NHC's fisheries engineering solutions also include designing facilities to exclude fish from entrapment in water intake facilities, support for hatchery facilities, and instream habitat improvement.

Effective fish passage and fisheries engineering design integrates hydrology, geomorphology, hydraulics, and fish biology and physiology. The resulting projects help ensure that dams, road crossings, and other structures maintain or restore access to valuable fish habitat, and enhanced instream conditions.

NHC provides a wide range of assessment and design services for fish passage, screening, ecological flow management, and other fisheries related projects. Target species vary in different areas, but include salmon, steelhead, bull trout, cutthroat trout, cui-ui, and lamprey.

Our experienced staff apply fish passage design criteria in projects and work collaboratively with agencies and stakeholders to develop innovative designs in especially challenging or unique situations. Our services include:

  • Identifying and Assessing Fish Passage
  • Designing Fish Passage and Screening Structures
    Fish ladders, fish bypass and collection facilities, and fish screens at diversion.
  • Modifying Natural and Artificial Barriers to Enhance Passage
  • Habitat and Operations Improvements
    Enhancements for hatchery intakes and instream habitat improvement.
  • Field Services
    Bathymetric surveying, and flow and velocity measurements.
  • Analysis and Studies
    Hydrologic and hydraulic analysis, and fluvial geomorphology and sedimentation studies.
  • Modeling Hydraulic Performance
    Physical and multi-dimensional models developed to evaluate aquatic habitat condition in streams and around water infrastructure facilities.


NHC has developed designs for passage by aquatic organisms at dams, diversions, intakes, road crossings, grade control structures, and other infrastructure. Our work includes protecting and restoring conditions for upstream and downstream migration for a full range of life stages, and considering the specific temporal and behavioral patterns of the target species.

Past examples of our work include:

  • Barrier Assessment and Monitoring
    Field surveys, barrier classifications, geomorphic evaluations, fish counts and tracking, and flow and velocity measurements.
  • Barrier Removal
    Retrofits for culverts, bridges, grade controls, low water crossing, and other facilities that pose migration problems.
  • Naturalized Channels, Roughened Riffles, and Fishways
    Roughened channel or step pool designs to mimic natural channel processes to create habitat and allow fish passage.
  • Fish Ladders
    Conceptual designs, construction documents, and oversight and management of construction of fish ladders and other structures to facilitate upstream passage.
  • Fish Bypass, Collection, and Screening
    Hydraulic design for downstream passage at facilities ranging from major hydroelectric dams to local irrigation and water supply facilities.
  • Construction Services and Post-Construction Evaluation
    Construction and post-construction evaluation of projects, including detailed flow and velocity measurements over a range of stream flows.
  • Varied Climates
    Expertise for a wide range of project types, many species of concern, and varied river morphologies and hydrologic conditions ranging from arctic to tropical climates.

NHC prefers to apply a geomorphic or stream restoration approach to aquatic organism passage to achieve sustainable infrastructure design. Where conditions require hydraulic structure design, we apply a range of simple to sophisticated tools tailored to the project. Our designs are based on field data, understanding of the temporal and physical components necessary for biological success, and detailed modeling and analysis.

For challenging or complex situations, NHC applies our in-house capabilities in 3-dimensional numerical modeling and physical modeling to better understand fine-scale hydraulic conditions that may affect fish passage. By collaborating with project stakeholders, aquatic ecologists, and fisheries biologists, NHC develops functional and sustainable solutions based on both sound science and consensus from multiple perspectives.

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