However, this type of model investigation is difficult and expensive to 

 conduct, and each area in which such an investigation is contemplated 

 must be carefully analyzed. In view of the complexities involved in con- 

 ducting movable-bed model studies and due to limited funds and time for 

 the Noyo River and Harbor project, the model was modeled in cement 

 mortar (fixed-bed) at an undistorted scale of 1:75, and a tracer material 

 was obtained to qualitatively determine the deposition of riverine sedi- 

 ment (degree of accretion, etc.) at the river mouth for existing conditions 

 and the offshore breakwater plan. 



Model and Appurtenances 



The model reproduced the lower 15,000 ft of Noyo River, both Noyo 

 Harbor and Dolphin Marina (located on the south bank), Noyo Cove, ap- 

 proximately 5,500 ft of the California shoreline on each side of the river 

 mouth, and underwater topography in the Pacific Ocean to an offshore 

 depth of 60 ft with a sloping transition to the wave generator pit elevation 

 of -75 ft. The total area reproduced in the model was approximately 

 12,000 sq ft, representing about 2.4 square miles in the prototype. A gen- 

 eral view of the model is shown in Figure 4. Vertical control for model 

 construction was based on mean lower low water. Horizontal control 

 was referenced to a local prototype grid system. 



Model waves were generated by a 45-ft-long piston-type generator. 

 The horizontal movement of the piston plate caused a periodic displace- 

 ment of water incident to this motion. The length of the stroke and the 

 frequency of the piston plate movement were variable over the range nec- 

 essary to generate waves with the required characteristics. In addition, 

 the wave generator was mounted on retractable casters which enabled it to 

 be positioned to generate waves from the required directions. 



A water circulation system (Figure 3) consisting of a 6-in. perforated- 

 pipe water-intake manifold, a 3-cfs pump, and a magnetic flow tube and 

 transmitter was used in the model to reproduce steady-state flows through 

 the river channel that corresponded to selected prototype river discharges. 



An Automated Data Acquisition and Control System (ADACS), designed 

 and constructed at WES (Figure 5), was used to secure wave-height data at 

 selected locations in the model. Basically, through the use of a minicom- 

 puter, ADACS recorded onto magnetic media the electrical output of capaci- 

 tance-type wave gages that measured the change in water-surface elevation 

 with respect to time. The magnetic media output of ADACS was then ana- 

 lyzed to obtain the wave-height data. 



All elevations (el) cited herein are in feet referred to mean lower low water (mllw) un- 

 less otherwise cited. 



10 



Chapter 2 The Model 



