This paper explores the concept that deltaic-estuarine geomorphology is a function of the dominant processes. It has been traditional to recognize river, wave and tidal processes as the principal controls on the gross morphology of deltas. To a lesser extent, these processes are also recognized as significant controls on the shape of estuaries. The complex deltas of the Southeast Asian region contain active deltaic plains and often extensive abandoned deltaic plains which preserve an imprint of the processes which have shaped them. In northern Australia, where estuaries are more extensive than deltas, similar geomorphological features can be recognized and the relative significance of river, wave and tide processes assessed as these systems evolve. Channel pattern provides insights into the dominant process and the response of these systems to changes in boundary conditions as the system evolves. A better understanding of the natural morphodynamic adjustments of these systems to changing boundary conditions will provide some indication of the probable direction and magnitude of future adjustments on these systems, but discriminating natural change from human-induced changes will be a greater challenge.