12 



BULLETIN 114, U. S. DEPARTMENT OF AGRICULTURE. 



about 500, and from a mile above Hamilton Ridge Road to the river 

 swamp the width is about 700 feet. The upper part of the drainage 

 area is comparatively well drained, and largely under cultivation. 

 It is rolling, with good fall to the swamp. Below the Orangeburg 

 Road the land is much natter, with little fall to the swamp above the 

 Morrison Road, but with a break of 10 to 25 feet to the swamp level 

 below that road. The largest cultivated tracts are along the main 

 swamps where drainage is better than on higher land farther back. 

 The chief need of this section is better drainage channels to bring the 

 water to the main streams. 



The proposed improvement in Boggy Swamp consists of a ditch 

 throughout the length of the swamp. (See figs. 2 and 3.) From sta- 

 tion 0, the upper end, to station 130, the ditch should be constructed 

 by hand labor, with 3-foot bottom width, 6-foot depth, and side 

 slopes J to 1, giving a top width of 9 feet. From station 130 

 to station 758, the lower end, the ditch is to be constructed with a 

 floating dipper dredge. At the upper end of this portion there will 

 be a minimum dredge ditch, and the bottom width will gradually 

 increase to 30 feet at the lower end. The total fall in Boggy Swamp 

 is 100 feet, varying from 17 feet per mile at the upper end, to 1.8 feet 

 per mile at the lower end. (See fig. 3.) The Boggy Swamp ditch 

 is not carried on to the Savannah River Swamp, but ends about 1£ 

 miles below the Hamilton Ridge Road. Below the end of the pro- 

 posed ditch the water will overflow the swamp, but the lands adjoin- 

 ing this portion of the swamp are much higher and will not be dam- 

 aged, while the swamp itself is subject to overflow from the Savannah 

 River and will be of little value for agriculture. 



The following table summarizes the data and hydraulic computa- 

 tions for the proposed Boggy Swamp ditch : 



Table 1, — Data and computations for Boggy Swamp ditch. 



[Side slopes of ditch, -J to 1.] 



Stations. 



Depth. 



Bottom 

 width. 



Fall. 



Com- 

 puted 

 velocity. 



Watershed. 



Com- 

 puted 

 ditch 

 capacity. 



From — 



To— 



Area. 



Run-off. 



00 

 40 

 80 

 130 

 143 

 260 

 355 

 423 

 440 

 531 

 570 

 628 

 660 



40 

 80 

 130 

 143 

 260 

 355 

 423 

 440 

 531 

 570 

 628 

 660 

 758 



Feet. 

 6 

 6 

 6 



7 

 7 

 7 

 7 

 7 

 7 

 7 

 7 

 7 

 7 



Feet. 

 3 

 3 



3 



14 

 14 

 14 

 14 

 14 

 20 

 22 

 24 

 28 

 30 



Ft. per 

 foot. 



0.00225 

 .00325 

 . 00206 

 . 00206 

 . 00051 

 .00171 

 .00171 

 . 00171 

 .00087 

 . 00087 

 .00087 

 .00087 

 .00034 



Feet per 



mile. 



11.88 



17.16 



10.88 



10.88 



2.69 



9.03 



9.03 



9.03 



4.61 



4.61 



4.61 



4.61 



1.80 



Feet per 

 second. 



Acres. 



600 



1,150 



1,800 



2,000 



3,300 



4,175 



8,000 



14,800 



15,875 



17,025 



19, 850 



29,475 



31,900 



Cu.ft. 

 per sec. 



Cu.ft. 

 per sec. 









3.6 



3.7 



2.9 



5.15 



5.15 



5.15 



4.1 



4.15 



4.25 



4.35 



2.8 





130 

 700 

 360 

 630 

 630 

 630 

 675 

 740 

 815 

 960 

 655 











620 

 665 

 715 

 835 

 930 

 1,005 



