(d) Test Period . October 1963 to August 1964. 



(e) Problem . Texas City, Texas, is located on the south- 

 west shore of Galveston Bay about 9 miles northwest of Galveston and about 

 9 miles from the Gulf of Mexico. The Texas City ship channel connects the 

 Texas City Harbor with the gulf (Fig. 6-43). Most of the city's developed 

 area occupies an east-west ridge through the central part of the city. 



The ridge slopes from an elevation of +15 feet MSL to about + 5 feet MSL. 

 Hurricane surges can raise the water levels at Texas City to an elevation 

 of about +15 feet MSL with significant waves of 6-second period and 8- 

 foot height in the unsheltered areas and of 3.5-second period and 3- foot 

 height in the sheltered areas. The corresponding maximum waves in the 

 wave trains are about 15 feet and 5.6 feet in height, respectively. A 

 seawall is proposed to protect Texas City and vicinity from hurricane 

 surges. This flood protection project consists of new and enlarged lev- 

 ees and seawalls (approximately 16 and 1.3 miles in length, respectively), 

 together with the necessary drainage and stop-log structures, a naviga- 

 tion opening, and pumping plants. 



(f) Purpose of Model Study . The model study was conducted 

 to derive design data of cover layers for (1) a rubble-mound structiore 

 with an impermeable wall standing vertically at the centerline of the 

 structure, (2) an earth levee with the bayside protected by rubble layers, 

 (3) a vertical-faced seawall with a rubble mound protecting the natural 

 ground on the bayside, and (4) a vertical-faced structure with no rubble 

 mound on either the bayside or the landside. Data on the quantities of 

 overtopping water and the forces exerted on the vertical-faced seawall by 

 both breaking and nonbreaking waves were also desired. 



(g) The Model . Tests were conducted using section models 

 of the proposed structures in a wave flume 119 feet long, 5 feet wide, 

 and 4 feet deep. The model was designed by Froude's law. A linear scale 

 of 1:35 was selected on the basis of the estimated size of armor units re- 

 quired for stability, the capabilities of the available wave generator, 

 and the water depths at the toe of the proposed seawall. A plunger-type 

 wave generator was used and the wave heights were recorded by printed- 

 circuit rods and a CEC oscillograph. The protective cover layer for a 

 considerable part of the proposed seawall would consist of quarrystone 

 armor units; granite was the only natural stone available within economic 

 hauling distance. When quarried by blasting, the armor stones were nearly 

 rectangular with moderately rough surfaces and rather sharp corners and 

 edges. Since model stones of this type were not available, and the proc- 

 ess of hand-shaping and hand-sizing model stones similar to the prototype 

 stones was tedious and costly, concrete blocks with four smooth faces and 

 two slightly roughened faces were cast for this study. The weights and 

 specific weights of the different sizes of armor stones with the 50-percent 

 sizes and specific weights of the core stone, blanket stone, crushed stone, 

 riprap, A- rock londerlayer, and toe stone used in the model tests are given 

 in Table 6-6. The model weights were determined from equation (6-39) , con- 

 sidering that the specific weights of the water in model and prototype were 

 62.4 and 64 pounds per cubic foot, respectively, and that the linear scale 

 was 1:35. 



410 



