DRAINAGE OP BLACK AND BOGGY SWAMPS, S. C. 



15 



IMPROVEMENTS IN BLACK SWAMP WATERSHED. 



The watershed area of Black Swamp is comparatively flat, except 

 the lower or southern portion, which is more rolling, with a good fall 

 toward the swamp. A large part of the flat land is under cultiva- 

 tion, while the remainder is mostly flat bays and ponds with a thick 

 covering of bushes and trees. 



The swamp or wet land along this stream is 100 to 300 feet wide 

 for the first few miles below the source, then 400 to 600 feet for a few 

 miles, and finally reaches 800 to 1,000 feet width at the lower end. 

 There is no well-defined channel, and during wet seasons the entire 

 swamp is covered with water several feet deep. The growth in this 

 swamp is a thick, tangled mass of vines, briars, canes, and bushes, with 

 a fairly heavy growth of timber. The total fall is 79 feet, quite 

 sufficient to give good drainage to these lands, and for the greater 

 portion of the swamp it is quite uniform, as may be seen from the 

 profile (fig. 3). It varies from 12.5 feet per mile at the upper end to 

 1.3 feet per mile for a short distance at the lower end. 



The proposed improvements on Black Swamp consist, as shown in 

 figures 2 and 3, of a dredge ditch starting at the Southern Railway 

 just south of Furman and continuing down the swamp until overflow 

 water from the Savannah River is encountered. This will require 

 a ditch about 10 miles long. The depth should be 7 feet, with side 

 slopes of J to 1. The ditch should start with a 14-foot bottom width, 

 increasing to 30 feet. At the lower end the estimated capacity of 

 the ditch is less than the calculated run-off, and consequently some 

 flooding is to be expected. No harm will result from this, however, 

 as the lower end of the swamp will be flooded by exteme high water 

 in the Savannah River, and the lands bordering the swamp He 15 to 20 

 feet above its level and have good natural drainage. The table 

 below summarizes the data and computations for the Black Swamp 

 ditch. 



Table 2. — Data and computations for Black Swamp ditch. 











Side slop 



:s of ditch 



Jtol.) 









Station. 









Com- 

 puted 



Watershed. 









Depth. 



Bottom 

 width. 



Fall. 







puted 

 ditch 











From — 



To— 









velocity. 



Area. 



Run-off. 



capacity. 











Feet per 



Feet per 



Feet per 





Cu.ft. 



Cu.ft. 







Feet. 



Feet. 



foot. 



mile. 



second. 



Acres. 



per sec. 



per sec. 



00 

 80 

 102 

 169 

 180 

 240 



80 

 102 

 169 

 180 

 240 

 299 



7 

 7 



7 

 7 

 7 

 7 



14 

 14 

 14 

 14 

 14 

 14 



0. 00237 

 .00200 

 . 00200 

 . 00200 

 . 00127 

 . 00127 



12.51 

 10. 56 

 10.56 

 10.56 

 6.71 

 6.71 





2,000 

 2,175 

 3,575 



7,050 

 7,850 

 10, 775 

























4.55 

 4.55 





555 

 555 



453 



299 



320 



7 



14 



. 00127 



6.71 



4.55 



12, 600 



529 



555 



320 



339 



7 



16 



.00095 



5.02 



4.1 



12,9C0 



542. 



560 



339 



407 



7 



20 



. 00095 



5.02 



4.3 



16,650 



7C0 



710 



407 



432 



7 



22 



. 00095 



5.02 



4.35 



17, 425 



732 



775 



432 



460 



7 



22 



. 00095 



5.02 



4.35 



17, 925 



753 



775 



460 



526 



7 



30 



. 00023 



1.31 



2.4 



18, 500 



777 



565 



