The proposed breakwaters at Noyo included the use of concrete armor 

 units (Accropodes). Since the porosity of these armor units differs from that 

 of rock and since the units could not be reproduced to scale (due to cost and 

 time requirements), two-dimensional wave transmission tests were conducted 

 at a scale large enough to have negligible scale effects (i.e., 1 :43) to deter- 

 mine the correct transmission through the proposed structures. This transmis- 

 sion then was duplicated at a scale of 1 :75 using a rock cross section, and the 

 three-dimensional model structures were built accordingly. These tests are 

 detailed in Smith and Hennington (in publication). 



Parts of the existing jetties at Noyo River entrance are rubble-mound 

 structures. Experience and experimental research have shown that consid- 

 erable wave energy passes through the interstices of this type structure; 

 thus, the transmission and absorption of wave energy became a matter of 

 concern in design of the 1 :75 scale model. In small-scale hydraulic models, 

 rubble-mound structures reflect relatively more and absorb or dissipate rel- 

 atively less wave energy than geometrically similar prototype structures 

 (L6M6haute" 1965). Also, the transmission of wave energy through a rubble- 

 mound structure is relatively less for the small-scale model than for the 

 prototype. Consequently, some adjustment in small-scale model rubble- 

 mound structures is needed to ensure satisfactory reproduction of wave- 

 reflection and wave-transmission characteristics. In past investigations 

 (Dai and Jackson 1966, Brasfeild and Ball 1967) at WES, this adjustment 

 was made by determining the wave-energy transmission characteristics of 

 the proposed structure in a two-dimensional model using a scale large 

 enough to ensure negligible scale effects. A section then was developed 

 for the small-scale, three-dimensional model that would provide essen- 

 tially the same relative transmission of wave energy. Therefore, from pre- 

 vious findings for structures and wave conditions similar to those at Noyo, 

 it was determined that a close approximation of the correct wave-energy 

 transmission characteristics would be obtained by increasing the size of 

 the rock used in the l:75-scale model to approximately 1.5 times that re- 

 quired for geometric similarity. Accordingly, in constructing the rubble- 

 mound structures in the Noyo River and Harbor model, the rock sizes 

 were computed linearly by scale and then multiplied by 1.5 to determine 

 the actual sizes to be used in the model. 



The values of Manning's roughness coefficient, n, used in the design of 

 the main river channel were calculated from water-surface profiles of 

 known discharges in the prototype. From these computations and experi- 

 ence, an n value of 0.030 was selected for use in the main river channel. 

 In addition, based on experience, an n value of 0.050 was selected for 

 overbank roughness. Therefore, based on previous WES investigations 

 (Miller and Peterson 1953, Cox 1973), the various model areas from the 

 Noyo Harbor entrance extending upstream were given finishes that would 

 represent prototype n values of 0.030 and 0.050. 



Ideally, a quantitative, three-dimensional, movable-bed model investi- 

 gation would best determine the effects of the proposed structures with 

 regard to the deposition of sediment at the river mouth and in Noyo Cove. 



Chapter 2 The Model 



