Introduction Much of the sediment derived from the land is stored permanently in deltas. Deltas also can be temporary repositories for sediment that later is deposited into deeper water. Most of the world's largest submarine fans are linked to large deltas and rivers. As a consequence, a focus only on active Holocene systems will teach us very little about how submarine fans work because most submarine fans are built during lowstand when the river mouth is at the margin edge. Most present day shelf profiles are actually buried fluvial profiles formed during the last lowstand.
Many important issues remain to be resolved in delta research, one of which is outlined below.
My intent is to present some of these key research issues and to develop a specific research program to resolve some of the main problems in understanding the role of deltas in sediment transport and storage. An important, but poorly understood area of research, relates to wave-influenced deltas and particularly the origin and storage of sediment. The traditional depiction of wave-influenced deltas assumes that all of the sediment is derived directly from the river. Analysis of many modern delta systems, such as the Brazos, Sao Francisco, and Danube, shows that this assumption may be wrong and demonstrates a much more complicated origin. The river plays a critical role in the trapping of sediment carried by longshore drift.