Nonkinematic Effects in Storm Hydrograph Routing

The propagation of flood waves down very long prismatic rectangular channels was numerically simulated using the full St. Venant equations in the full equations (FEQ) model. The importance of nonkinematic effects on the behavior of each flood wave was quantified by calculating the dimensionless width of the simulated looped rating curve, which is directly related to the sum of the nonkinematic terms in the equation of motion. Dimensionless loop widths, WL, were found to be closely related to the dimensionless wave period, (tau), of Ponce et al. for a wide range of simulated bed slopes, channel widths, Manning n-values, and inflow hydrograph rise times. Since the variables defining (tau) can be estimated prior to detailed modeling, ranking of streams in order of decreasing values of estimated (tau) should roughly correspond to ranking in order of increasing nonkinematic effects. However, backwater and expansion/contraction effects are not captured by (tau).