FLOW OF WATER IN DREDGED DRAINAGE DITCHES. 30 
due to irregularities and vegetation in the channel. It is likely that 
a lower value of n would have been obtained for a bankful stage. 
(See Plate X, fig. 2; and figs. 5 G, and 6 /.) 
SOUTH FORKED DEER RIVER AT CAMPBELL’S LEVEE ROAD. 
Experiments were conducted on the river channel at the Camp- 
bell’s levee road, near Jackson, to determine the values of n for three 
different but consecutive courses, viz: Old channel (straight and 
erooked) and new, irregular, dredged channel. The relation of these 
courses as to location and algnment is shown in figure 6X. A 
good comparison for the courses can be made, since the values of n 
for the different courses were computed from the same discharge 
measurements, made from a suspension footbridge at the upper 
end of the old straight course, so that any error in discharge would 
not materially affect the relative values of n. The results obtained, 
and a detailed description of the three different courses, are given im 
GAGING a 
~~. 
-~__ 
Ss 
=— 
Fic. 6x.—Slope course at Campbells Levee, South Forked Deer River, near Jackson, Tern. 
Table No. 3, measurements 63 to 76 (see Plate Xl and Plate XII, fig. 1, 
for views of the three courses). ‘The conditions found in the two sec- 
tions of the old channel are typicai of those prevailing in channels in 
this section of the country. The dredged channel is more irregular 
in shape of cross section than is the usual dredged channel in this 
part of the country. (For cross sections and variation im size of 
channel along slope courses see figs. 5 H,5 1,5 7,6 K,6L, and 6M.) 
in comparing the values of nm obtained for the fourth measurement 
im each channel (Table 3, measurements 66, 70, and 75) it is seen 
that the values are 0.0367, 0.0619, and 0.146 for the dredged, old 
straight, and old crooked channels, respectively; also that the slopes 
required for the same discharge is more than three times as much 
for the old straight channel as for the dredged channel, and about 
nine times as much for the old crooked channel. In order to show 
the relative capacities for these three courses of channel, for the 
values of n given above, the foilowing computations were made 
in which the slope, hydraulic radius, and cross-sectional area for 
measurement 66 were used. 
