1. Relating to or consisting of any material that has been carried or deposited by running water: "The result of the soil being washed by water may result in an alluvial valley or an alluvial deposit; all of which consist of earth and sand that has been left by rivers, floods, etc."
2. Etymology: borrowed from Medieval Latin alluvium, alluvius, "washed against", from Latin alluere, "to wash against"; from al-, a form of ad- before l, "to, against", + -luere, a combining form of lavere, "to wash".

An underground water supply which comes from porous rock, sand, gravel, etc.: "The alluvial aquifer provided the community with ground water that made it possible for their wells and springs to exist."

A sedimentary deposit (fragments of material) built up by an overloaded stream that is obstructing the stream channel: "The alluvial dam of soil composed of sand, silt, and clay were blocking the flow of water."

The accumulation of sediment (mud, sand, etc.) deposited by fresh running water into a channel: "The alluvial deposits are controlled by the kinds of channels, vegetation covers, channel densities, sources of geology, climates, and dirt surface deformations."

A gently sloping fan-shaped or a wedge-shaped mass of sediment deposited by a stream where it comes from a narrow canyon onto a plain or valley floor: "Alluvial fans accumulate at and spread from the base of dry mountain ranges where a mountain stream, no longer confined to its narrow channel, deposits its coarse sediment into a large sloping apron-like structure at the point where it comes out onto the plain."

"When a stream divides into branching and intertwining lower channels that are separated by islands or sandbars they twist their way through the fan format and carry sediment from the fan's apex to its fringes and so become alluvial fans."

"Alluvial fans also develop in front of melting glaciers, when the water flows out from the ice and spreads out a large amount of coarse debris with it."

"Large aluvial fans have deposits that exist in different sizes within the fan, with the bigger pieces of sediment dropping closest to the mountains and the finer materials deposited farther away as the water moves along."

A small plain where gravel, sand, and mud are deposited on the sides of rivers during floods: "Alluvial flats usually form where streams leave earth materials in river valleys or deltas."

Gold that can be found in soil and water sediment deposits.

These deposits are usually found around rivers, streams, or any other sort of running water.

The process of dredging (scooping out of the mud) or drift mining to exploit materials that have been carried, washed, or deposited by running water: "Alluvial mining involves the processing of deposits that are carried by rushing streams and located where the water slows down to remove certain elements from a riverbed, channel, etc."

Various kinds of valuable mineral particles that have been transported and deposited by a river or a stream: "The old prospector mined the alluvial ore along the river, hoping to find gold."

A gently sloping tract of land alongside a river that periodically overflows thereby depositing clay, silt, gravel which has been brought downstream where the water slows down: "We decided to pitch our tents on the alluvial plain near the river because it was flat and sandy."

"The waste plains look desolate and barren; however, they may be rich in minerals that have been washed down by the river."

 

The soil, clay, silt, or gravel that is left by a flowing water surface which slopes down and away from a mountainside and merges with a plain or wide valley floor: "Alluvial slopes are made up of the surface soil from hills or mountains that have been washed by rain during which time the slanting hills deposit bushes and other vegetable matter, plus sand, dirt, and mud slides; all of which are carried down and left in areas of flat land; such as, valleys."

1. A fine-grained fertile soil deposited by water flowing over flood plains or in river beds.
2. Fertile soil that can be found in aquatic communities (living in or on water for all or a substantial part of the life span; generally restricted to fresh water or inland waters).

A soil developed on flood plains and deltas, having only the characteristics of the clay or silt or gravel carried by rushing streams and deposited where the streams slow down: "The alluvial soils leave a fine-grained earth material consisting of very tine particles of sand and clay, all of which are deposited by water flowing over flood plains or into river beds."

"The farmers near the mouth of the river found that the alluvial soils were much more fertile than the land farther away from the river."

A flat terraced embankment or a gently sloping geomorphic surface of loose, unconsolidated earth material that has built up next to the sides of a river valley: "The geology teacher told his students that an alluvial terrace is a land area that came from a previously formed floodplain that was formed by a stream or river."