The material deposited by a river is called sediment. The bits of organic debris such as leaves and stems is detritus. Sediment includes detritus, inorganic material such as pebbles, sand, clay and other rock bits.
the bank of a river
I would call it a sediment.
A fan-shaped area of fertile land is typically called a "alluvial fan." It forms when a river slows down and spreads out as it exits a mountainous region, depositing sediment in a cone or fan shape. This fertile land is often suitable for agriculture due to the rich nutrients in the sediment.
sand bars
because of the black sediment left after fllods
The soil that is lost due to erosion is called sediment. Sediment can be carried away by water, wind, or ice, leading to a loss of fertile soil and degradation of land quality.
Wind erosion and sediment transport by wind.
The abrasion and attrition combined with hydraulic action on the river bed and the river banks erode away the underlying rock which results in small grains of rock we call sand. Depending on the speed of the river and the size of the particles, the sand will be deposited by the river at different stages (usually though it is found near the mouth of the river).
loess
sediment
Much of the coarser sediment material supplied by rivers settles out near shorelines or on beaches.
You call the bits of soil sediment.