river digging
/ˈrɪvə ˌdɪɡɪŋ/originally US (now historical )
noun
1The action of prospecting for gold or diamonds near a river or stream, or in a riverbed.
2In plural A gold or diamond digging situated in such a place.
Origin
Mid 19th century; earliest use found in New York Journal of Commerce. From river + digging.