Fluvial processes can be categorized into two types. The first, overland flow , occurs when water flows down slopes of the land surface as a broad sheet. Overland flow carries with it surface particles, or sediment , from higher elevations to lower elevations, thereby contributing to the shaping of the landscape. The second category of fluvial processes is stream flow . Stream flow occurs when water occupies a trenchlike depression, or channel, in the landscape, and moves from higher elevation to lower elevation under the force of gravity.
Streams are capable of carrying large amounts of sediment.
Overland flow also contributes to stream flow. When overland flow meets a stream channel, that water becomes part of the stream and continues its downhill journey as stream flow.