Rivers dominate the upper delta plain. The Orinoco River splits into distributaries (caņos) at the apex of the delta. The principal flow is directed east across the delta through the Rio Grande and empties into the Atlantic Ocean at Boca Grande. The residual flow is transported primarily by Caņos Manamo and Macareo, two large distributary channels that originate near the delta apex at Barrancas and flow north and northeast, respectively. Distributaries carry the bulk of the sediment and water load of the river.

The landforms observed in the upper delta plain are related to active and abandoned channel belts separated by flood basins. As river levels change seasonally, water moves in and out of the flood basins. The size and distribution of the channel belts indicate that the principal flow of the Orinoco River has remained confined to the southern half of the delta throughout the Late Holocene (last few thousand years). By contrast, large distributary channels have avulsed (jumped out of old channels during floods and formed new channels) frequently and are responsible for the construction of the northern delta plain.

Current research topics include an investigation of links between fluvial activity and coastal processes. Because avulsions affect both the amount and location of sediment delivery to coastal zones, we hypothesize that avulsions in the upper delta can influence rates of coastal erosion or accretion. By reconstructing the avulsion history of the upper delta plain and comparing it to the lower delta coastal history, we will improve our understanding of geologic links between these two areas and their construction and the development of various habitats.

Another area of current research involves evaluating structural and lithologic controls on channel orientations and patterns. Faults near Tucupita trend to the northeast similar to the flow direction of many active and abandoned distributary channels. Channel courses that shift abruptly to the northwest may also correspond to faults in the subsurface. The low sinuosity of most channel segments probably corresponds to the low gradient of the delta and large quantities of delta plain muds, which inhibit lateral channel migration. Sinuous channel reaches are generally observed near the delta apex and may reflect the presence of relatively shallow Pleistocene(?) sand bodies that are being reworked by modern channels.