Bottom Profiles 



Knowledge of the underwater terrain is vital to the successful 

 deployment of an underwater power transmission system. Bottom profiling 

 is a prerequisite for establishing cable routes and site requirements and for 

 avoiding potential hazard areas such as steep ledges and narrow valleys. 



Since there are great distance-to-depth variations in the ocean bottom 

 profiles, the actual cable length to reach various design depths was used in 

 this study. Table 1 illustrates the variations in average distances involved in 

 reaching the various design depths off of selected coastal regions. A minimum 

 offshore distance of 21 miles and a maximum of 460 miles is noted in the 

 table, with a majority of offshore distances of less than 200 miles, only three 

 distances being greater than 200 miles. Therefore, it appeared feasible to 

 consider cable lengths at multiples of 10 miles, with specific design lengths of 

 50 and 100 miles. Design distances of bottom-contoured cable lengths were 

 established at 10, 50, 100, and 500 miles. 



Table 1. Bottom Profiles of Continental Margins 



Region 



Average Number of Miles From Coast to Reach a Depth of— 



600 

 feet 



2,000 

 feet 



6,000 

 feet 



10,000 

 feet 



15,000 

 feet 



20,000 

 feet 



East Coast 

 U. S. 



West Coast 

 U.S. 



Southeast 

 Asia 



South 

 Australia 



70 

 21 



110 

 51 



150 

 28 



155 

 48 



175 

 32 



190 

 72 



182 



55 



208 



110 



190 

 162 

 319 

 120 



_1 

 _1 



460 

 _1 



Ocean does not reach this depth except in isolated instances. Off the East Coast, 

 the West Coast, and South Australia the maximum depth is found approximately 

 3.5 miles from shore. 



