Subcritical Kinematic Flow in a Stable Stream

An evaluation of the shallow water equations in the lower 6.9 miles (11.1 km) of a stable, gently sloped tributary to the Susquehanna River showed that subcritical kinematic flow exists. Although loops were suspected, single-value rating functions within small statistical error were established at four points along the stream. Also, single Manning n-values within very small statistical error were established at each point. It was shown explicitly, however, that use of a single-valued rating function does not permit simultaneous use of a single resistance coefficient or vice versa. Use of a single resistance coefficient independent of stage will induce a loop rating function. This apparent inconsistency was resolved by reformulating the characteristic equations in terms of the exponent of the single-valued rating function used. Therefore, for the special case of subcritical kinematic flows, streamflow synthesis may be accomplished without resort to extrapolation of uniform flow formulas to unsteady nonuniform flow.