ELOW OF WATER ES DREDGED DRAINAGE DITCHES, 



&& 



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 J.) 



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 

 crooked) and new, irregular, dredged channel. The relation of these 

 courses as to location and alignment is shown in figure 6X. A 

 good comparison for the courses can he 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 

 mot materially affect the relative values of n. The results obtained, 

 and a detailed description of the three different courses, are given in 



Cable Bridrft 



6 «'« ST A T f 0N oio sr„ AiGHr 



Camp bells Levee Road 



Pro. 6x. — Slope course at Campbells Levee, South- Forked Deer River, near Jackson, Term. 



Table Nov 3, measurements 63 to 76 (see Plate XI and Plate XII, fig. 1^ 

 for views of the three courses). The conditions found in the two sec- 

 tions of the old channel are typical of those prevailing in channels hi 

 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 in size of 

 channel along slope courses see figs. 5 M,. 5 /, 5 J, 6 K, 6 L, and 6 MS) 

 In comparing the values of n obtained for the fourth measurement 

 in 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 following computations were made 

 in which the slope, hydraulic radius, and cross-sectional area for 

 measurement 66 were used. 



