This paper develops a geomorphological theory of tidal basin response (tidal instantaneous geomorphologic elementary response, or TIGER) to describe specific characteristics of tidal channel hydrodynamics. On the basis of the instantaneous unit hydrograph approach, this framework relates the hydrodynamics of tidal watersheds to the geomorphic structure of salt marshes and, specifically, to the distance traveled by water particles within the channel network and on the marsh surface. The possibility of determining the water fluxes from observations of geomorphic features is an appealing approach to the study of tidally driven flow rates. Our formulation paves the way to the application of recent results on the geomorphic structure of salt marshes and tidal networks to the determination of marsh creek hydrology. A case study shows how the asymmetry in the stage-velocity relation and the existence of velocity surges typical of the tidal hydrographs can be explained as an effect of the delay in the propagation of the tidal signal within the marsh area.