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for FQ is entered, all flows on cards QT and X2 are multipled by this value and the resulting flows are used in the subsequent calculations. e. Manning's "rill. (1) Since Manning's coefficient of roughness "n" depends on such factors as type and amount of vegetation, channel configuration and stage, several options are available to vary "n", When three "n" values are suffi- cient to describe the channel and overbank roughness, the first three fields of card NC ("n" value change) are used, Any of the "n" values may be per.- manently changed at any cross section by using another NC card. Often three values are not enough to adequately describe the lateral roughness variation in the overbanks in which case card NH ("n" value - horizontal) is used. The nwnber of "n" values used to describe the overbank roughness is entered as variable NUMNH in the first field, and the "n" values and corresponding cross section stations are entered in subsequent fields. These "n" values will be used for all subsequent cross sections unless changed by another NH card or NC card, Normally NH card "n" values should be redefined for each cross section with nuw ~eometry. (2) Data indicating the variation of Manning's "n" with river stage may be used in the program, Manning's "n" and the corresponding stage eleva- tion (beginning with the lowest elevation) are entered on card NV ("n" value - vertical) beginning in the second and third field, respectively, Variable NUMMY in field 1 is the nwnber of "n" values input on the NV cards, This option applies only to the channel area, (3) If for subsequent runs of the same job it is desired to multiply the "n" values specified on cards NC, NH, and NV by a multiplier, variable FN on card J2 may be used, The desired multiplier is simply entered as variable FN for each job, If the variable is left blank, all "n" values will be multiplied by one, If the value of FN is negative then the factor is multiplied by the channel "n" on the NC card but the. overbank "n" is not changed, . f, SolvinR for Manning's "n". (1) To determine Hanning's "n" from knoTnl high water marks along the river reach, the discharge, relative ratios of the "n" values for the channel and overbanks, and the water surface elevation at each cross section must be knoTnl. The "best estimate" of "n" for the first cross section must be entered on cat"d NC since it is not possible to compute an "n" value for this cross section, The relative ratio of "n" between channel and overbank is set by the first cross section and will be used for all subsequent cross sections unless another Ne card is used to change this ratio, High water marks are used for the computed water surface elevation by setting variable 3