When small pebbles are carried downstream in rivers, they bounce along the river bed. What type of transportation is this?

The type of transportation described is called “saltation.”

Saltation is a process where small particles, such as pebbles, are transported by a medium like water. Instead of being carried fully suspended, these pebbles bounce or leapfrog along the riverbed, which happens when the river’s flow is strong enough to lift them momentarily before they fall back down. This method of transport is important in the movement of sediment in rivers and contributes to the shaping of riverbanks and beds over time.