What is another term for Stream Processes?
Fluvial Processes
What is a stream?
Any area of channeled water flow
What is Sheet Flow?
over-land flow (spread out, even depth)
What is Stream Flow?
concentrated flow into a direct channel
What are Fluvial Processes?
a stream’s ability to shape a landscape, depending on CAPACITY and COMPETENCY
Define Capacity
total amount of material that the stream can move *depends on discharge- volume of water moving out.
Higher discharge = higher capacity
Define Competency
the size of material that can be carried by the stream
*depends on stream velocity.
Higher velocity = higher competency
Arises from kinetic energy- stream flow converts potential energy into kinetic energy (movement)
What is the Stream Gradient?
Stream Steepness, related to kinetic energy
Gradient = Steepness
What is the Base Level?
Level below which a stream cannot erode its valley
Ultimate base level = the ocean
Local base level = a local limit to erosion, such as a lake or resistant rock layer
Describe Stream Energy
Ability of a stream to erode and transport materials is dependent on its total amount of energy.
-Influenced by velocity, volume of water.
Energy used for erosion is not available for transportation and vice-verse
What is Stream Erosion?
Hydraulic action (movement of materials through pressure and shearing force) + Abrasion (mechanical erosion of stream bed by waters or solids in the stream) -occurs with both stream and sheet flow
What are the 3 types of stream transportation?
Solution Load
Suspended Load
Bed Load
Solution Load
Material dissolved and carried in stream (usually through chemical weathering)
“Kool-Aid” - dissolved throughout
Suspended Load
Small, clastic particles held aloft in water, with the energy of the water keeping them suspsended
- carried along in water, without contacting the stream bed
- more energy, more suspended load
- Kinetic Energy
Bed Load
Material pushed along the bottom by the water’s energy (rolling, bouncing along the bottom of the stream)
Saltation: skip/bounce
Traction: sliding along the bottom
Describe Deposition
Occurs when stream energy is no longer sufficient to transport load, results in sorting based on sizes.
-dramatic decrease in energy
-deposits/dumps material
(largest things drop first)
Braided rivers
river split into different channels (multiple, interwoven)
-more materials than the stream has the capacity to transport
Meandering Streams
The river’s form changes as undercuts and point bars migrate (curves = meanders)
-outside of the river has more energy at turns, inside is moving slower)
Inside = deposition
Where do deltas form?
At the end of streams
What are Nickpoints?
Hard rock on top of softer rock
What are graded streams?
Graded streams have reached a balance between erosion, transportation and deposition
-when uplift occurs, streams can return to active periods of down cutting.
