Fluvial Processes Flashcards
What are the three main processes involved in fluvial processes?
Erosion, Transportation, and Deposition
Define a stream.
Any channeled flow of water.
What do fluvial processes involve?
Running water, encompassing both overland flow and streamflow.
What is overland flow?
Unchanneled downslope movement of water.
What is streamflow?
Channeled movement of water along a valley bottom.
What is a valley?
Portion of terrain where drainage system is clearly established.
What is an interfluve?
Higher land above a valley, separating adjacent valleys.
Define drainage basin or watershed.
All area that contributes to overland flow, streamflow, and groundwater.
What is a drainage divide?
Line of separation between runoff descending to one drainage basin and another.
What describes the arrangement and organization of streams within a watershed?
Stream order.
What are first-order streams?
Smallest streams with no tributaries.
What is splash erosion?
Movement of particles downhill caused by raindrops colliding with the ground.
What are rills?
Tiny channels that form when volume of overland flow increases.
What is gully erosion?
Occurs after rills coalesce into fewer and larger channels.
What enhances erosion by streamflow?
Channeled surface flow increases volume and speed of water.
What is stream load?
Material collected in streams.
Fill in the blank: The size of the largest particle that a stream can transport is known as _______.
Competence
What is capacity in terms of stream transport?
Maximum load a stream can transport under given conditions.
What is alluvium?
Stream-deposited sediments that are typically smooth and round.
What happens to transported material when stream flow speed decreases?
It will be set down or deposited.
Describe perennial streams.
Permanent streamflow in humid regions.
What is a flood event?
An increase in stream discharge that can enhance erosion and deposition.
What is discharge in relation to streams?
Volume of flow per unit of time.
True or False: Urbanization increases infiltration due to impermeable surfaces.
False
What are the three dimensions of streamflow in a channel affected by?
Gradient, friction, and channel width/depth.
What are the four categories of stream channel patterns?
Straight channels, sinuous channels, meandering channels, braided channels.
What is downcutting in valley deepening?
Lowering of the streambed through hydraulic power and abrasive effect of bedload.
What causes knickpoint migration?
Intensified erosion that causes movement of knickpoint upstream.
What occurs during valley widening?
Lateral erosion of outside of curves occurs where flow speed is fastest.
What is headward erosion?
Erosion that cuts into interfluve at upper end of gully or valley.
Define stream capture.
Headward erosion causes one stream to be diverted to the basin of another stream.
What is a delta?
Depositional landform at the mouth of a river.
What is the process called when one stream extends its valley toward another stream?
Captor stream reduces a drainage divide
This process involves cutting the channel and capturing the flow of a beheaded or captured stream.
What happens to deposits at the mouth of a river?
Deposits build up, partially blocking the channel and forcing flow along new paths
This creates a maze of parallel channels called distributaries.
What is aggradation?
The process of deposition in valleys
It occurs anytime a stream loses power to transport its load.
During high-water periods, where is most sediment shifted?
Downstream
This occurs when the flow is fast.
What is a floodplain?
A low-lying, nearly flat alluvial valley floor periodically inundated with floodwaters
It forms where a meandering stream flows across a wide, level valley.
What are bluffs in the context of floodplains?
Higher elevation slopes on the outer edge of a floodplain
They are elevated areas that border the flat valley floor.
What forms when a meandering channel bypasses itself?
A cutoff meander
This may remain filled with water as an oxbow lake.
What is an oxbow lake?
A body of water formed from a cutoff meander
It may eventually dry up into a meander scar.
What is the significance of alluvium in valleys?
It is deposited anywhere on the valley bottom when a stream loses power
This process leads to the formation of layered beds of sediment.
What occurs during low-water periods in relation to sediment?
Flow is slowed and sediment is more likely to settle on the bottom
This can even raise the stream bottom.
Fill in the blank: The growth of a stream valley downstream involves sediments sorted during _______.
deposition
What creates a maze of parallel channels in river deltas?
Distributaries
They form as flow is redirected by deposits at the river mouth.
