to research and development studies as opposed to site specific project studies. 

 In view of the complexities and unknowns involved in conducting movable- 

 bed model studies and due to limited funds and time for the Camp Ellis Beach 

 project, the model was molded in cement mortar (fixed-bed) and a tracer 

 material was prepared to qualitatively define erosion and sediment patterns 

 along the beach. 



Model and Appurtenances 



The model reproduced about 2,438 m (8,000 ft) of the Saco Bay shoreline. 

 Camp Ellis Beach, the Saco River entrance, and bathymetry in Saco Bay to an 

 offshore depth averaging about -13.7 m (-45 ft) with a sloping transition to the 

 wave generator pit el of -30.5 m (-1(X) ft). The total area reproduced in the 

 model was approximately 1.952 m^ (21,000 ft^) representing about 19.4 km-^ 

 (7.5 square miles) in the prototype. A general view of the model is shown in 

 Figure 5. Vertical control for model construction was based on mean low 

 water (mlw). Horizontal control was referenced to a local prototype grid 

 system. 



Model waves were generated by a 24.4-m-long (80-ft-long), unidirectional 

 spectral, electrohydraulic, wave generator with a trapezoidal-shaped, vertical- 

 motion plunger. Vertical motion of the plunger was controlled by a 

 computer-generated command signal, and movement of the plunger caused a 

 displacement of water which generated required test waves. The wave genera- 

 tor was mounted on retractable casters which enabled it to be positioned to 

 generate waves from required directions. 



A water circulating system (Figure 4) consisting of 152-mm (6-in.) 

 perforated-pipe water-intake and discharge manifolds, a 0.085-cms (3-cfs) 

 pump, and sonic flow transducers with a multiprocessor 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, designed and con- 

 structed at WES (Figure 6), was used to generate and transmit control signals, 

 monitor wave generator feedback, and secure and analyze wave data at selec- 

 ted locations in the model. Through the use of a microvax computer, the 

 electrical output of parallel-wire, capacitance-type wave gages, which varied 

 with the change in water-surface elevation with respect to time, was recorded 

 on magnetic disks. These data then were analyzed to obtain the parametric 

 wave data. 



A 0.6-m (2-ft) (horizontal) solid layer of fiber wave absorber was placed 

 around the inside perimeter of the model to dampen wave energy that might 

 otherwise be reflected from the model walls. In addition, guide vanes were 

 placed along the wave generator sides in the flat pit area to ensure proper 

 fomiation of the wave train incident to the model contours. 



10 



Chapter 2 The Model 



