Which of the following best describes the process of delta formation?

Delta formation is primarily characterized by the slow deposition of sediments as the flow velocity of a river decreases. This process occurs when a river meets a standing body of water, such as an ocean or a lake. The velocity of the river's flow decreases significantly upon entering this larger body of water, which causes the sediment being carried by the river to settle and accumulate at the river's mouth.

The accumulation of sediments over time leads to the development of a delta, which is typically characterized by its triangular or fan-shaped appearance. Factors such as the amount and type of sediment supplied by the river, as well as the water body's dynamics, can influence the shape and size of the delta.

In contrast, other choices underscore different aspects of river and sediment dynamics that do not effectively lead to delta formation. Consistent sediment erosion with high flow velocity may lead to riverbank erosion, while rapid deposition during heavy rainfall may not create a stable delta structure, as it lacks the sustained deposition necessary for delta formation. Similarly, an immediate shifting of river channels with no retention of sediment would disrupt the sediment accumulation process essential for building a delta.