The Fluvial Process
Erosion by Streamflow
Once surface flow is channelized
hydraulic power
gravity (steep gradient)
turbulence
When all factors are high - erosion is highest
mountains and floods
Sierra Nevada Story
Transportation
and Deposition
attrition
- natural sizing,
rounding
and sorting
large boulders to fine, suspended silt
less sorted to well-sorted
dissolved load
- invisible minerals dissolved in solution
suspended load
- fine particles (silt) are suspended
saltation
- coarser material (like gravel and sand) bounce along
traction
- larger material dragged along (large rocks)
degrading streams - eroding
cutting down
often on steeper gradient
aggrading
streams - depositing
low gradient (flat), decreased velocity
more sediment than it can transport
silt-filled
deltas
and estuaries
hydraulic mining day- Yuba River in Marysville 1870s
Graded streams
neither
degrading
or
aggrading
( flowing in equilibrium)
cutting on outside, depositing on inside
River Questions
Stream Channels
three (3) dimensional and complex nature
gravity must overcome friction from bank walls & bottom
straight channels - unusual in nature; often along faulted rock
meandering channels
- sinuous channels with defined loops
thalweg
- indicating the deepest part of channel
stream flow will wander in even the straightest channels
likely to transform into a sinuous channel
braided streams
- multiple, interwoven streams filled with sediment
within main stream channel
often broad
streams
loaded with silt
Canada and Alaska
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