determined experimentally using a wide range of wave conditions and bottom 

 materials and are valid mainly for the breaker zone. 



Noda's scaling relations indicate that movable-bed models with scales in the 

 vicinity of 1:60 (model to prototype) should be distorted (i.e., they should have 

 different horizontal and vertical scales). Since the fixed-bed model of Port Huron 

 Harbor was undistorted to allow accurate reproduction of short-period wave and 

 cunent patterns, the following procedure (which has been successfully used and 

 validated for undistorted models) was used to select a tracer material. Using the 

 prototype sand characteristics (median diameter, D50 - 0.17-0.90 mm, specific 

 gravity = 2.65) and assuming the horizontal scale to be in similitude (i.e., 1:60), 

 the median diameter for a given vertical scale was then assumed to be in 

 similitude and the tracer median diameter and horizontal scale were computed. 

 This resulted in a range of tracer sizes for given specific gravities that could be 

 used. Although several types of movable-bed tracer materials were available at 

 WES, previous investigations (Giles and Chatham 1974; Bottin and Chatham 

 1975) indicated that crushed coal tracer more nearly represented the movement of 

 prototype sand. Therefore, quantities of crushed coal (specific gravity - 1.30; 

 median diameter, D50 = 0.42-2.89 mm) were selected for use as a tracer material 

 throughout the model investigation. 



Experimental Conditions and Procedures 



Selection of experimental conditions 



Still-water levels. Still-water levels (swls) for wave action models are 

 selected so that various wave-induced phenomena that are dependent on water 

 depths are accurately reproduced in the model. These phenomena include 

 refraction of waves in the project area, overtopping of harbor structures by waves, 

 reflection of wave energy from various structures, and transmission of wave 

 energy through porous structures. 



Water levels on the Great Lakes vary from year to year and from month to 

 month. Also, at any given location, the water level can vary from day to day and 

 hour to hour. Great Lakes' water level data for the period 1918-1996 indicate that 

 higher water levels usually occur during the spring and early summer and lower 

 water levels occur during the winter months. For Lake Huron, the minimum and 

 maximum lake levels generally occur in February and July, respectively. During 

 the period of record, the average lake level for Lake Huron was +0.58 m (+1.9 ft). 

 The highest level was +1.6 m (+5.5 ft) in October 1986, and the lowest level was 

 -0.2 m (-0.7 ft) in March 1994. The seasonal variation in the mean monthly level 

 of Lake Huron usually ranges from 0.21 m (0.7 ft) to 0.6 m (2.0 ft), with an 

 average variation of 0.4 m (1.3 ft). 



Seasonal and longer variations in the levels of the Great Lakes are caused by 

 variations in precipitation and other factors that affect the actual quantities of 

 water in the lakes. Wind tides and seiches are relatively short-period fluctuations 

 caused by the tractive force of wind blowing over the water surface and by 



Chapter 6 Physical Model 35 



