The Chinook River estuary is located near the mouth of the Columbia River in Washington. The estuary has historically provided important rearing habitat for juvenile salmonids from the Columbia River estuary. However, due to growth and development, considerable amount of this habitat has been reduced. The loss of habitat and the reduction in salmonid populations are attributed primarily to the construction in the early 1920s of a Highway 101 overpass across the mouth of the Chinook River and the installation of a tide-gate under the overpass. In 2003, PNNL staff (formerly with Foster Wheeler) participated a restoration design study and supported a project team which included representatives from Washington State Department of Fish and Wildlife (WDFW), Ducks Unlimited, Sea Resources and other agencies. The objective then was to provide baseline hydrologic and hydrodynamic information for the Chinook River estuary study area and to evaluate and design a restoration alternative that would best meet the management goal while also providing flood protection to properties upstream of Chinook River Valley Road. The modeling analysis conducted then provided information on water levels, velocities, salinity, and inundation during both normal tides and storms under existing conditions and under the restoration alternatives (Foster Wheeler Environmental Corporation, 2003).
Since then, WDFW in collaboration with the Washington Department of Transportation (WSDOT) and Ducks Unlimited, Inc. replaced two of the Chinook River tide gates in late 2007. It is possible to mechanically lift the tide gates to fully open position during the summer to allow maximum tidal exchange and inundation and close the gates either partially or fully during the winter storm conditions to provide protection from flooding. WDFW who manages the project site contacted PNNL and requested assistance in designing a new management regime such that operation of the tide gates at the mouth of the estuary best accommodates flood protection and habitat restoration needs. WDFW has requested refinement of the hydrodynamic model to incorporate the new tide gates and conduct
additional hydrodynamic modeling (water surface elevations, currents, and salinity) based on the various gate opening scenarios that are under consideration.
This work proposed by WDFW will be conducted through a grant from Bonneville Power Administration (BPA). The hydrodynamic modeling component work will provide information in support of the restoration and project operation design will be funded directly through a contract between BPA and PNNL. All communication and reporting will be through BPA project manager (Ms. Marchelle Foster) who will be PNNL primary contact, and will forward updates, reports, etc. onto WDFW.
II. Objectives
The overall objective of this modeling study is to help inform and design a new Chinook estuary management regime based on tide gate operation evaluated for a typical tidal year. It is expected that this will be accomplished using a hydrodynamic model of the Chinook estuary based on the model previously calibrated and developed in 2003. The model will be upgraded to incorporate the new tide gates and the model code upgraded to allow improved salinity intrusion and robust state-of-the-art computational capability.
To accommodate the project requirement of 1-year long runs, the hydrodynamic model of the Chinook River estuary be upgraded from RMA-10 model to the NOAA recommended Finite Volume Coastal Ocean Model (FVCOM) code. The upstream inflows will be generated using the HEC-HMS model as before.
The specific objectives of the study are as follows:
• Upgrade the existing hydrodynamic model of Chinook River from RMA-10 to FVCOM and re-validate corresponding to the Year 2003 calibration condition. The hydrodynamic model will validated using the water surface elevation, velocity, and salinity data measured during the 2003 calibration period and will include the presence of the leaking tide gate.
• Select a typical tidal year and generate 1-year long hydrologic and tidal model inputs
• Refine the model to accommodate the new tide gate and test the ability to simulate the following conditions
o One tide-gate fully open
o Two tide-gates fully open
o Half gate open
• Conduct the hydrologic and hydrodynamic model for the following scenarios
o Typical tidal Year (3 tide gate scenarios)
o 100 year storm (100 year tide and storm surge elevation with 100 year runoff)