A more thorough explanation:

ALLUVIAL MINING

Alluvial mining is the process of extracting sand and gravel from the bed of a river or stream.

One example of alluvial mining is panning for gold in a river. Another example is using heavy machinery to extract sand and gravel from a riverbed for construction purposes.

Alluvial mining involves removing materials from the bed of a river or stream. This can be done manually, as in the case of panning for gold, or with heavy machinery. The extracted materials are often used for construction purposes, such as building roads or bridges.