KECLAIMING OVERFLOWED LANDS IN MISSISSIPPI. 29 
In computing the capacities of the creek floodways, where the 
ditches parallel the levees, the discharge of the section represented 
by hcfglik (fig. 9) was computed by taldng the line/^7^^ as the wetted 
perimeter for the area, and n equal to 0.030. The discharges of the 
areas abhl and cdef were then computed, taking n equal to 0.040 ; 
the sum of these three results gave the total capacity of the floodway. 
CONSTRUCTION. 
No attempt is made here to provide full specifications for the pro- 
posed work. It is intended under this caption merely to point to 
y — J^ __Waten_Sut'face_ b^ 
Channe/ 
m J.G.H,del. 
'I, 
Fig. 8.— Sketch illustrating method of computing capacity of river floodway, Big Black River, Miss, 
some of the more important details that have governed the design 
of the improvements and to emphasize those features of location and 
construction which are vital to the success of the system. 
DITCHES, 
The minimum ditch planned has a bottom width of 6 feet, side 
slopes of 1 to 1, and a depth of flow of 6 feet; such a ditch can be con- 
structed economically with the same type of machine that builds the 
^ b Wate r Surface C d^ v 
Le\/ee 
'M A j.6.H.clel 
Fig, 9.— Sketch illustrating method of computing capacities of creek floodways, Big Black River, Miss., 
levees. Ditch No. 4, in district No. 1, can be constructed econom- 
ically by a floating dredge because its size is sufficient to justify 
installing such a machine. The width of the berm is independent 
of the width of the ditch, but varies with the depth of excavation. 
For cuts of 10 feet or less a berm of 10 feet is planned; for cuts greater 
than 10 feet a berm of 12 feet is recommended. 
In existing channels, where clearing is the only improvement 
needed, all timber and underbrush should be cut, aU debris removed, 
and all stumps cut level with the ground. The widths of right-of-way 
for ditches were computed by taking 3 J times the width of the top, 
plus the width of both berms. 
