132 



TRANSPORTATION OF DEBRIS BY RUNNING WATER. 



tion giving highest capacity for traction is rela- 

 tively shallow and broad; with steeper slopes, 

 the reduction of capacity through retardation 

 of the current by the channel sides is relatively 

 small; and the general effect of steepened slopes 

 is increased capacity. 



Each set of values of a constant exhibits an 

 orderly progression, marred only by minor ir- 

 regularities due to the inaccuracies of graphic 



TABLE 27. Observed and computed quantities illustrating the 



computation. The results recorded in Tables 

 28 and 29 are much less orderly. It is to be 

 noted that the remarkable orderliness in the 

 present case is- not due to high precision of 

 the data but to the fact that the values of C 

 and R assembled in Table 27 had previously 

 been adjusted, as described in Chapter II, in a 

 manner which made them orderly with respect 

 to slope. 



influence of slope on the relation of capacity to form, ratio. 



CONTROL OF CONSTANTS BY DISCHARGE. 



Table 28 and figure 44 exhibit quantities and 

 curves illustrating the influence of discharge on 

 the relation of capacity to form ratio. The 

 data employed are those of grade (C) with a 

 channel slope of 1 per cent, and of grade (G)with 

 a channel slope of 2 per cent. Of the seven 

 curves in the figure, four were determined by 

 three observational points. As three is the 

 minimum number of given points for the deter- 

 mination of a curve of this type, each curve 

 passes through all the points. In each of the 

 other cases four points are given by the ob- 

 servations, and it was not found possible to pass 

 one of the curves through all the points. If 

 the formulas are correct, the incompatibility 

 indicates errors of the data. Errors of similar 

 magnitude inferably affect the three-point 

 groups of data, and this inference qualifies the 

 determination of the curves and their equations. 

 Of the same general tenor is the fact that the 

 four curves under grade (C), pertaining to dis- 

 charges which increase in arithmetic progres- 



sion, do not exhibit an orderly progression as 

 to shape. 



Grade CO Grade fGJ 

 S-l.0% 5-2.0% JL 



--ZOO 



I Q '1.119 



.734 



100 



? 1_ 



.0 .Z .4- 



FIGURE 44. Relation of capacity, C, to form ratio, R. 

 of the function C-iu (1 a R ) 

 scale of R horizontal. 



.4- 



The variation 

 with discharge. Scale of ^vertical; 



