Natural sand and gravel are generally found in river and stream valleys where they have been deposited by water, and in ridges and hills where they were left behind by receding glacial action and subsequently altered by erosive forces.
In their natural state, sand and gravel are usually loose, easily handled, and, being composed of a range of grain sizes, are readily compacted while retaining good internal drainage characteristics, making them a preferred and stable material for fills and as a base course for pavements and other structures. Sand and gravel are also key ingredients in ready mixed concrete and asphalt.