normal tides and hurricane surge heights upstream and downstream from 

 barrier sites, current velocities throughout the bay system, the salinity 

 regimen of the bay, and the rates of diffusion and flushing of pollutants 

 discharging into the bay; and (b) provide data that were in turn used to 

 calibrate and improve the numerical model and its capability of predict- 

 ing surge elevations at other locations along the Texas coast. 



(7) Physical Models . At the conception of the Galveston Bay 

 surge study, an existing model of the Houston Ship Channel (Fig' 3-71), 

 constructed to scales of 1:60 vertically and 1:600 horizontally, was 

 available for studies on barrier effects on normal tides, currents, 

 salinities, and dispersion patterns throughout the bay and to determine 

 the number and position of tidal openings in that part of the barrier 

 crossing the bay. This model did not reproduce the entire bay complex 

 and was not equipped with the necessary apparatus for generating hurri- 

 cane surges. Because it was not economically feasible to add this capa- 

 bility and expand the model, a second general model was constructed for 

 the sole purpose of investigating the effects of the hurricane barriers 

 on surge elevations resulting from a hurricane approaching from the gulf. 

 Since a greater degree of distortion was possible for this type of inves- 

 tigation; the model was constructed to scales of 1:100 vertically and 

 1:3,000 horizontally. This model (Fig. 3-72) was referred to as the 

 Galveston Bay hurricane surge model. Each of the general models was 

 equipped with the necessary apparatus to satisfactorily reproduce normal 

 tides, current velocities and patterns, and freshwater inflow. In addi- 

 tion, the Houston Ship Channel model was capable of reproducing salinity 

 intrusion and flushing characteristics, and the Galveston Bay surge model 

 was equipped with a hurricane surge generator. Several section models 

 were constructed in a flume (Fig. 3-73) to determine the discharge char- 

 acteristics of the existing barrier beaches and the proposed navigation 

 and tidal barrier openings. The undistorted-scale section models were 

 constructed to a scale of 1:100; the distorted-scale section models were 

 constructed to the same scales as the Houston Ship Channel model or the 

 Galveston Bay surge model, as appropriate. 



(8) Test Procedures . Before initiating testing for the bar- 

 rier studies, each model had been adjusted to satisfactorily reproduce 

 all pertinent prototype phenomena. The Galveston Bay surge model was 

 adjusted using tide and velocity information obtained in the Houston 

 Ship Channel model and hurricane surge elevation data collected by U.S. 

 Army Engineer District, Galveston, personnel during Hurricane Carla. 

 The prototype hurricane data were first subjected to a numerical anal- 

 ysis, in which the effects of local wind and normal tide were removed. 

 The Galveston Bay surge model was then adjusted to reproduce these modi- 

 fied prototype surge data. Each navigation opening and typical tidal 

 openings to be tested were first calibrated in an undistorted-scale sec- 

 tion model to determine the discharge characteristics. The openings 

 were then subjected to similar tests in a distorted-scale section model. 

 During these latter tests, the size or shape of the model openings were 

 adjusted to achieve the same discharge characteristics as determined in 

 the undistorted-scale calibration tests. Photos of the undistorted- and 

 distorted-scale models of the Alpha barrier navigation opening are shown 



64 



