ABSTRACT
This chapter examines the initial production of the sediment that is supplied to, and transported by, river channels. Much of this sediment originates in the production zone of the headwater regions (see Figure 2.1). Sediment is originally derived from the underlying bedrock which, having been broken down by weathering, is then transported down-slope by processes of mass movement and water erosion. River bank erosion also produces a significant proportion of the sediment transported in river channels. In glaciated drainage basins, vast quantities of sediment are produced by glacial erosion. Aeolian (wind blown) material may also provide a source of sediment. Figure 4.1 provides a generalised schematic illustration of the main sediment sources. It should be noted that the relative dominance of these various processes varies considerably across different environmental settings.
