A river delta is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarely) another river that cannot carry away the supplied sediment.
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Deltas are wetlands that form as rivers empty their water and sediment into another body of water, such as an ocean, lake, or another river.