Lecture 13: Surface Water Flashcards
What does River Morphology refer to?
The shape of a river channel and the evolution of the channel shape over time
What are Bedrock channels?
Places where the river is directly incised in bedrock and are typical of the headwaters region of a river
What are Alluvial channels made of?
Unconsolidated sediment called aluvium
Where are alluvium channels usually found?
Downstream and in lower gradient environments
What is the change in channel morphology between Bedrock channels and Alluvial channels?
Alluvial channels change in morphology more rapidly than bedrock channels
What do Bedrock channels typically form?
Pools and falls
How is rock usually removed in bedrock channels?
Rock is usually removed both by physical erosion to form alluvial/sediments and chemical dissolution
What kind of load and speed do bedrock channels have?
A small suspended load (clear water) with a slower velocity because of pools
What are the two types of Alluvial Channels?
Braided Channels and Meandering Channels
What are braided channels comprised of?
Multiple channels separated by bars of coarse material (sand and gravel)
What causes the channels and bars to change position and size in braided channels?
Erosion and deposition
Where do Braided channels usually form?
- Where discharge is variable over time
- Banks are easily eroded
- Common in glacier fed rivers
What kind of channels are common in glacier fed rivers?
Braided Channels
What occurs in Meandering channels?
The channel forms a large sinuous loop and each bend is the meander
Where are Meandering Channels most common?
In fine grained alluvium (clays and silts) and low gradient channels where coarder bed material is located on the outside and flow is faster
Where is flow faster in Meandering channels?
On the outside of meanders
What is a Cut Bank and Point Bar?
Erosion on the outside of a meander and erosion on the inside of a meander
What is an Oxbow lake?
A lake formed when a meander pinches off
What do Rivers sit in?
River valleys
What do River Valleys include?
The river channel and the region nearby that feeds water to the river
What kind of River Valleys do Bedrock sit in?
Deep, narrow, V-shaped valleys
What kind of River valleys do Alluvial channels sit in?
Wide, shallow valleys
What is Lateral erosion caused by?
The migration of meanders which widens valley
What is a Floodplain?
When meanders move laterally widening the river valley
