GGR201H1 Chapter Notes - Chapter 6: Terminal Velocity, River Source, Thalweg
22 Feb 2017
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Document Summary
The depth of the water table determines whether or not channels carry baseflow between storms, which in turn, is decided predominantly by regional climate: ephemeral channels flow occasionally throughout the year. Common in arid and semi-arid environments: perennial channels flow year round. Over geologic time, streams grade their channels. Mountainous or bedrock streams usually have a transport capacity which exeeds their sediment supply, whereas lowland, or alluvial streams are the opposite. Riparian or near-stream areas, are usually biologically very active. Rivers shape these areas, but are also shaped by them. If sediment supply exceeds transport capacity, the additional deposition causes channel aggradation which increases channel slope downstream of the point of deposition, which increases transport capacity and helps move the material downstream. If transport capacity exceeds sediment supply, erosion will scour the channel bed and reduce the channel bed slope. Sediment supply can vary tremendously over time. In mountain drainage basins, sediment is supplied through mass wasting.
