They serve as conduits through which the products of erosion are transmitted from source areas to sedimentary sinks. Rivers not only transport the products of erosion but they themselves can erode the landscape. However, the influx of eroded sediment sometimes exceeds the sediment transport capability of a river and new landforms are created through deposition. Rivers attempt to maintain a dynamic equilibrium whereby they transport the water and sediment load provided from upstream sources without undergoing significant morphological alterations. Four main variables act in concert to govern channel morphology.
Rivers convey the water and sediment discharge supplied from the drainage basin.
This discharge, along with the slope of the valley on which the river flows, and the composition of the channel boundary represent the major variables controlling river morphology. Variation in the balance of these variables will elicit a response in one or more of the dependent variables such as channel pattern, sinuosity, channel slope, width, depth, velocity and channel roughness. Channel pattern is the most obvious expression of a rivers adjustment to changes in the independent variables. The primary subdivision is into single channel and multi channel forms. Single channel systems are divided into straight and meandering channels.