Riverbed (noun)

The bottom of a river, especially when consisting of rocks, sand, or gravel.

Origin:

Late 16th century, from river + bed.

Examples:

1. The riverbed was dry and cracked due to the drought.
2. The riverbed was covered in pebbles and boulders.
3. The riverbed was home to many species of fish and plants.
4. Gold was once mined from the riverbed during the California Gold Rush.
5. The riverbed was a popular spot for summer swimming.