Tillamook Bay Model Study: Hydraulic Model Investigation

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Tillamook Bay Model Study: Hydraulic Model Investigation

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Fisackerly, George M.

The Tillamook Bay model was of the fixed-bed type, constructed to scales of 1:500 horizontally and 1:100 vertically, and reproduced Tillamook Bay, Oregon, in its entirety and a suitable area of the Pacific Ocean. The model was equipped with the necessary appurtenances for accurate reproduction and measurement of tides, tidal currents, salinity intrusion, freshwater inflow, shoaling distribution, and other significant prototype phenomena. The purpose of the model study was to determine the optimum alignment and length of south jetty at the entrance to Tillamook Bay. Model verification tests indicated that the model hydraulic and salinity regimens were in satisfactory agreement with those of the prototype for comparable conditions. It therefore can be assumed that the model provided quantitative answers concerning the effect of the proposed plans on the hydraulic and salinity regimens of the bay. The optimum plan consisted of existing conditions plus a 7000-ft south jetty located 1200 ft from the north jetty. Lengths greater than this do not modify the shoaling pattern to any great degree and should be considered only if additional protection for navigation is required.