The lower Ord River of Western Australia experiences a tidal range of 5.9 m at its mouth and has a typical "funnel-shaped" or exponentially converging form. The tide within the lower Ord behaves as a standing wave, and tidal amplitude decreases at a cosine rate from a maximum at the mouth to zero over a distance which corresponds to one-quarter tidal wavelength. The point of zero amplitude corresponds to the upstream limit of tidal influence and to the point at which channel convergence ceases. Because of the cosine variation in amplitude, tidal prism decreases upstream at a nonlinear rate. Depth and width convergence rates tend to balance frictional dissipation and produce a condition of equal work per unit area of channel bed by coadjusting with tidal prism. Bedload transport patterns and an upstream increase in sinuosity are attributable to an upstream increase in tide wave asymmetry. In contrast to the Ord, the King River, located within the same region and dynamic environment, is highly sinuous and has parallel banks and a low width/depth ratio. The tide in this channel is similar to a progressive wave. Correspondingly, amplitude is constant from the mouth to a point only a short distance downstream from the limit of tidal influence; tidal prism decreases at a constant linear rate. This situation seems to be attributable to a low value for the ratio of channel length to tidal wavelength.