A river winding its way down to the sea, from its mountain source, will inevitably choose the lowest land through which to flow. By the time the river approaches the sea the speed at which it is travelling will have decreased considerably, thus allowing the water to drop its load of sediment and other solids.
These solid particles (alluvium), therefore, form the land pockets which are characteristics of the various branches of a river delta. Owing to the slow pace of a river at this stage, it will wind its -way round any elevated land points rather than go over them.
Deltas are most likely to form where the sea, into which the river flows, is particularly calm for most of the year. Notable deltas in the world include the Mississippi (the largest) the Ganges, end the Nile. A delta is so called because it is the name of the fourth letter of the Greek alphabet whose shape it resembles.
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