Two modifications to the model during the test program where: (a) 

 the cross-sectional area through which water flowed from West Bay into 

 the outflow channel was adjusted by changing the cross-sectional area 

 between West Bay and the Outflow Channel; and (b) an artificial barrier 

 was installed in the model from the inner end of the north jetty to 

 approximately the +10. 0-foot contour MSL on Bolivar Peninsula for tests 

 26 and 27 (see Fig. 7-8). The barrier was high enough to eliminate all 

 flow over Bolivar Peninsula in that area. The only overtopping of Bolivar 

 Peninsula or Galveston Island during any test was in the immediate vicin- 

 ity of the Galveston Harbor Entrance. 



(9) Summary of Test Results . The average discharge and water 

 surface elevation at each gage location for each test was determined, and 

 the tests were grouped according to the approximate elevation of the Gulf 

 of Mexico; i.e., -1.5, +3,0, +4.5, +5.9, and +8.5 feet MSL. Discharge 

 coefficients were defined for the inlet using the orifice equation: 



Q = qAv/2^Ah ' (7-11) 



where 



Q = the discharge through the opening 



Cjj = the coefficient of discharge 



A = the cross-sectional area of the entrance 



g = the acceleration of gravity 



Ah = the difference between the gulf water surface elevation 

 (averaged data from gages 1 and 2 in Fig. 7-8) and the 

 bay water surface elevation (averaged data from gages 

 11 and 14 in Fig. 7-8). 



The results of the study of the discharge coefficients are shown in Fig- 

 ure 7-10. The coefficient varied from 0.3 to 0.6 with an average value 

 of 0.47 for hurricane surge conditions. The area of the entrance was 

 determined from a cross section taken at the position of gage 5 (see 

 Fig. 7-8); the area varied with the appropriate water surface elevation 

 measured at gage 5 for each flow condition. 



The accuracy of these data apparently centered on four major limita- 

 tions: 



(a) The Houston Ship Channel model used for the tests is a 

 distorted-scale model; therefore, the model was verified by 

 adjustment of the roughness of the model until known prototype 

 conditions were reproduced. Since adjustment was based on normal 

 tidal conditions, the assumption was that the model roughness 

 applied to conditions of the prototype where water surface above 

 high tide exists. Although extensive tests in the model could 



494 



