Large areas of the lower delta plain are frequently inundated by astronomical tides, fluvial discharge, or rainfall. The ground water is saline to brackish, the water table is shallow, the surface is densely vegetated, and surficial sediments are generally organic rich. In the lower delta plain, dwellings are elevated on poles and the indigenous people are mostly hunter-gatherers.

The geomorphology and shoreline morphology of the lower delta are highly variable. The eastern lower delta extends from the mouth of the Rio Grande (Boca Grande) north to Boca Araguao and is dominated by the principal flow of the Orinoco River and tidal influences, which produce a complex network of anastomosing channels and mangrove-covered islands. The northeastern area has a slightly smaller tidal range than Boca Grande and is characterized by a combination of sandy and muddy  accretionary shorelines, including several prominent northwest-trending mud capes. The suspended sediments that form these large arcuate features are only partly derived from the Orinoco. It is estimated that as much as 50% of the muds are derived from the Amazon and other coastal rivers of northeastern South America. The Guayana current transports these sediments northwest along the inner continental shelf to the Orinoco Delta and ultimately, to the Gulf of Paria. The northern lower delta plain extends west of Boca Macareo to the mouth of Cano Manamo at Boca Guanipa, and the muddy shoreline of this region is experiencing rapid coastal erosion. Boca Guanipa is an exception to this generalization; muddy shoreline accretion over the past 20 years has been rapid.

Some of the most interesting aspects of the lower delta plain geology are the mud capes and mud cape accretion as a mechanism of coastal progradation. Longshore currents cause northwest-directed mud-cape progradation, which in turn, deflects river mouths to the northwest. The presence of arcuate, northwest-trending landforms and the convergence of many distributary channels at discrete points located inland from the coast suggest that the most recent episode of mud-cape accretion was preceded by several Late Holocene accretionary episodes. Collectively, these observations suggest that mud-cape development has played a pivotal role in the construction of the delta plain.

Geo-environmental analysis of this part of the delta will include evaluating the flow of water through the swamps and marshes and determining the natural history of these wetlands. This will lead to a better understanding of the evolution of the channel network as well as the natural succession associated with swamps and marshes.