A single-input linear system model and a multiple-input linear system model are compared to a finite difference model. Comparisons are based on the ability of the models to predict discharge at the downstream end of a 24.14-km reach of prismatic channel. Four types of channels and two slopes covering a wide range of conditions are evaluated. The single-input model compares favorably in cases where flood wave celerity does not vary greatly with discharge. The multiple-input model can be made to compare favorably in all cases. Linear model parameters cannot be set accurately without calibration, except in the case of rectangular channels. The single-input model is approximately one sixth as costly as the finite difference model, and the multiple-input model is approximately one half as costly for the conditions investigated.