Question

how and when sandbars are formed in a river channel ​

Answer 1

Barrier bars or beaches are exposed sandbars that may have formed during the period of high-water level of a storm or during the high-tide season. During a period of lower mean sea level they become emergent and are built up by swash and wind-carried sand; this causes them to remain exposed.

Answer 2

Barrier bars or beaches are exposed sandbars that may have formed during the period of high-water level of a storm or during the high-tide season.During a period of lower mean sea level they become emergent and are build up by swash and wind-carried sand,this causes them to remain exposed.