Surface Water Flashcards
River Morphology
referring to the shape of a river channel and the evolution of the channel shape over time
Bedrock channels
places where the river is directly incised in bedrock, and are typical of the headwaters (higher gradient) region in a river
Alluvial channels
made up of unconsolidated sediment called alluvium. These channels are normally further downstream in lower gradient areas
channel morphology changes more rapidly for ___ than for ____
alluvial channels, bedrocks channels
Types of alluvium channels
braided and meandering channels
Bedrocks Channels typically form:
series of pools and falls, rock is removed both by physical erosion to form alluvium/sediments and chemical dissolution of the underlying rock
Braided channels
Comprised of multiple channels separated by bars typically comprised of relatively coarse material (sand and gravel). Channels and bars change position and size as the stream erodes and deposits sediment.
Brained channels typically form where
Discharge is variable over time and banks are more easily eroded
Braided channels are common in
glacier-fed rivers
Meandering channels
A channel that forms a sinuous loop where each bend is a “meander”.
Meandering channels are common in
fine-grained alluvium (clays, silts primarily), and in low gradient channels
Alluvium
composed of primarily silt and clays
Coarser material is located on the ____ of the meanders, where flow is _____
outside, faster
Meanders migrate ____ over time
Downstream
What causes the migration of meanders
active erosion and deposition processes in the river channel
Oxbow Lake
Happens when the migration of a meander slows due to a more resistant bank material resulting in slower erosion, the meander behind it may catch up leading to the formation of an oxbow lake.
