its called silt
Silt.
bits and pieces of rock get carried away.
Sediments, such as sand, silt, and clay, are fine bits of rock and soil that are deposited on land by a river. These sediments are carried by the river's current and then settle on the river banks and floodplains when the water slows down. Over time, these sediments contribute to the formation of fertile soil and landforms in river valleys.
silt
Sediments such as pebbles, sand, and silt that are carried and eventually deposited by a river are known as alluvium. Over time, these sediments can accumulate and form features like riverbanks, floodplains, and deltas.
Rock Snot
You can be carried by hand or me carried by a river. It depends on what size.
The rock-filled rapids in the Nile River are called cataracts. They are natural obstacles formed by boulders and rocks that create turbulent waters, making navigation challenging. The Nile has six cataracts located in southern Egypt and northern Sudan.
sediment
The process is called erosion. When bits of rock are carried away by flowing water, they can be broken down into smaller pieces and transported downstream. Erosion can shape landscapes by wearing down rock and soil over time.
The rock material carried away by a river is called sediment.
....rock filled rapids.