M.P. O'Brien


A model of the estuary of the Columbia River was built and tested at the University of California, Berkeley, during the years 1932 to 1936, to study the effects of proposed changes in the navigation channels on the currents and sediment movement. The project was sponsored by the North Pacific Division of the Corps of Engineers, and the engineering results were reported at that time in internal memoranda. The basis for the selection of the scale ratios and other factors affecting the design of the model were reported in some detail (O'Brien, 1935), but only a brief note was published regarding the operation and the accuracy of the model (Johnson, 1948). In some respects this model is still unique, and a description of it may be of interest to the coastal engineers. This paper deals primarily with the model itself and not with the practical problems of channel maintenance and improvement, but some information regarding the regimen of the Columbia is necessary background for understanding the problems which were to be studied in the model. Figure 1 shows the configuration of the estuary, the jetties, and the ship channel. The river was then unregulated; the freshwater discharge exhibited an annual cycle with an average annual flow of 235,000 second feet, an average summer freshet discharge of 660,000 second-feet, and an average low-water flow of 70,000 second-feet. The tide shows a diurnal inequality, with the long run-out following higher high water; the diurnal range of tide is 8.5 feet, and the average range is 6.5 feet. Freshet flows affect the range and lag of tide in the river section above the estuary to such a degree that the published USC and GS Tide Tables were valid only for the months September through May and not for the freshet season. The range of tide is approximately constant from the ends of the jetties to Harrington Point; the lag over this reach is approximately two hours. At low river stages the tide is evident as far as Bonneville, 140 miles from the mouth; the tide wave progresses with steadily decreasing amplitude and there are no nodal points. The tidal prism varies both with range of tide and river stage; at low river stages, the prism corresponding to an 8 foot range is between 600,000 and 700,000 acre feet.


navigation channel; Columbia River Estuary; field study

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