SERVICES

OEI works with a broad range of clients from local and regional governments and non-profit organizations to individual land owners.  Our work focuses on combining traditional field-based approaches with state-of-the-art geospatial data analysis and numerical modeling techniques to quantify and predict hydrologic, geomorphic, and ecosystem processes.
STREAM RESTORATION & FISH PASSAGE IMPROVEMENT
 

Planning and design of effective restoration projects requires consideration of the limiting factors for species recovery, the geomorphic and hydrologic processes operating at both watershed and reach scales, and the myriad of project constraints such as property boundaries, flood risk, and existing infrastructure.   

 

We utilize a variety of tools to help navigate these complexities including detailed field observations, monitoring and geospatial data analysis, and numerical hydrologic and sediment transport models.  Our integrative approach has

Simulating water depths and velocities relative to fish passage criteria to evaluate a roughened ramp design in Porter Creek

helped us develop successful watershed-scale restoration plans and site-specific restoration designs for projects ranging from adding in-stream structures to stabilize stream banks and build habitat complexity, to replacing fish passage barriers, to modifying channels and levees to restore floodplain connectivity.

 

     Salt Creek Bank Stabilization and Habitat Enhancement Project

      Sonoma Resource Conservation District & Cal. Dept. of Fish & Wildlife

 

     Vineyard Stormwater Enhancement Project-Gully Repair & Floodplain Restoration

      Sonoma Resource Conservation District & EPA

 

     Porter Creek Fish Passage Improvement Project

      Bioengineering Institute & Cal. Dept. of Fish & Wildlife

 

     Purrington Creek Geomorphic Investigation and Habitat Enhancement Plan

      Gold Ridge Resource Conservation District & Coastal Conservancy

 

         Porter Creek Fish Habitat Enhancement with Large Wood Structures

       Sonoma Resource Conservation District & Cal. Dept. of Fish & Wildlife 

FLOOD HAZARD MITIGATION
 

Design of sustainable flood mitigation strategies requires consideration not only of hydrologic and hydraulic conditions but also of the need for preserving habitat and geomorphic function.  We utilize a wide variety of hydrologic models ranging from simple lumped-parameter empirical models to complex distributed physically-based models, and both one- and two-dimensional hydraulic and sediment transport models.

 

These tools have helped us develop, evaluate, and design successful mitigation alternatives involving road crossing improvement, levee modification, flood control bypasses, channel reconfiguration, and sediment management strategies.  Many of the flooding projects we've worked have involved an extensive collaborative stakeholder coordination process to facilitate development of equitable and feasible solutions that best serve the interests of the people and wildlife they affect.

 

     Easkoot Creek Hydrologic, Hydraulic, and Sediment Transport Study

      Marin County Flood Control and Water Conservation District

 

     Green Valley Road Flood Mitigation Alternatives Analysis

      Gold Ridge Resource Conservation District

 

     Elk River & Freshwater Creek Historical Flooding Analysis

      Rankin, Sproat, Mires, Beaty & Reynolds  

 

     Zone 6 Drainage Master Plan

      Alameda County Flood Control District and Wood Rodgers, Inc.

Designing a flood bypass system to reduce chronic road flooding on Green Valley Creek
Simulating groundwater recharge in the Dutch Bill and Green Valley Creek watersheds using a distributed hydrologic model to assist in restoration prioritization planning
WATERSHED MODELING AND PLANNING
 

Ensuring adequate water supply and environmental flow availability has become an increasingly important concern for our society as we strive to accommodate an increasing demand for water in the face of ongoing climate change and drought conditions.  We work on water availability studies at a wide variety of scales ranging from evaluating individual proposed projects to quantifying the spatial and temporal variations in surface water and groundwater conditions for regional watershed planning efforts.

 

We utilize integrated surface water/groundwater models to quantify groundwater and streamflow conditions, characterize flow availability conditions for habitat restoration planning, evaluate the sustainability of existing and proposed land- and water-uses, and assist with climate change adaptation planning by evaluating future hydrologic conditions using global and regional climate model predictions.

 

     Dutch Bill & Green Valley Creek Flow Availability Analysis

      Gold Ridge Resource Conservation District

 

     Water for Fish & Farms Project

      Napa County Resource Conservation District

 

     Preservation Ranch Streamflow Monitoring and Hydrologic Analysis

      Premier Pacific Vineyards

 

 

GEOMORPHIC ANALYSIS
 

Consideration of geomorphic processes is a critical component in designing sustainable projects pertaining to habitat restoration, land development, or flood control.  We are well-versed in both fluvial and hillslope geomorphology and have extensive experience performing sediment transport modeling and analysis, monitoring changes in bed sediment composition in relation to fish habitat, performing fluvial geomorphic assessments for stream restoration design planning, conducting landslide mapping and slope stability analysis, and performing sediment source analyses for managing sediment loads and achieving TMDL requirements. 

 

     Lagunitas Creek Fine Sediment Investigation & Monitoring Plan

      Marin Municipal Water District

 

     Green Valley Creek Spawning Substrate Analysis

      Sonoma County Water Agency

 

     Preservation Ranch Landslide Mapping and Sediment Budget Analysis

      Premier Pacific Vineyards

 

     Geomorphic Habitat Assessment of Napa River Tributaries

      San Francisco Estuary Institute and Napa Resource Conservation District

Sediment budget development for Gualala River tributary watersheds and comparison to measured suspended sediment yield and TMDL targets
Evaluating the relationships between groundwater withdrawal and well field groundwater elevations relative to the timing of spawning habitat needs
GROUNDWATER INVESTIGATION
 

Increasing utilization of groundwater has led to increased awareness and new legislation at both the state and local levels designed to ensure sustainable groundwater availability.  We evaluate groundwater resources at multiple scales from regional hydrogeologic characterization and numerical groundwater flow modeling to evaluating water availability for individual projects proposing to use groundwater.  Much of our work has involved aquifer characterization, water availability analysis and recharge estimation, and characterization and evaluation of surface water/groundwater interaction.  We utilize a wide variety of methods in our groundwater work from interpreting driller's logs and performing pump tests to applying state-of-the-art integrated surface water/groundwater models.

    

   Sonoma County Soil Water Balance Modeling

WATER RIGHTS EVALUATION
 

OEI represents farmers, home owners and small water companies seeking new water rights or formalization of existing water uses and diversion facilities.  Through MOUs with Division of Water Rights, we have performed CEQA studies, analyses of water availability, and assessment of potential cumulative diversion impacts on anadromous fish according to criteria developed by State and Federal fisheries managers.  We have experience designing bypass retrofits to existing reservoirs to comply with minimum bypass flows and developing flow monitoring protocols to satisfy annual reporting requirements.

 

We utilize a variety of tools to investigate surface water/groundwater interaction including performing pump tests and seepage runs for wells expected to capture underflow from nearby streams and development of numerical surface water/groundwater flow models to evaluate proposed changes in diversion timing relative to fisheries habitat requirements.    

   Groundwater Evaluation of the South Main Steet Water System Project

      Lake County Special Districts Administration 

 

     Wilson Grove Aquifer Characterization and Recharge Study

      Gold Ridge Resource Conservation District

   

   Groundwater Availability Analysis, Sonoma County Water Scarce Areas

      Prepared over 60 analyses for individual property owners since 2004

    

 

 

 

 

 

 

 

CEQA ANALYSIS & PERMITTING
 

We have extensive experience assisting clients in understanding and complying with the hydrologic and sediment erosion aspects of the CEQA and state and local permit requirements.  We perform peak runoff and erosion analyses to support vineyard Drainage and Erosion Control Plans in Napa and Sonoma counties.  We assist cannabis cultivators in developing Water Resource Protection Plans and complying with new State Water Board and county-level land use regulations.  We perform groundwater availability analyses to determine recharge and sustainable yields and characterize aquifers and water supply wells for residential, agricultural, and winery development projects.  

Hydrology - Geomorphology - Engineering Geology