Stream Erosion & River Systems Flashcards
What does fluvial mean (2)?
- any stream-related processes
- any landform created or eroded by running water
What is the difference between streams and rivers?
- river: a main stream
- stream: generic term
What is hydrology?
the science of water and its global circulation
What are the eight elements of stream formation?
- sheetflow: surface water that is flowing downslope
- interfluve: an area of higher land that separates two adjacent river valleys
- rill: small-scale downhill-facing groove
- gully: larger downhill-facing groove
- confluence: the point at which two streams converge
- drainage basin: the area from which a stream collects its water
- drainage divide: the area between drainage basins
- continental divide: drainage basins which divide the continent
Are there any drainage basins that do not empty into the ocean?
yes: the Great Basin
What is a drenditic drainage pattern (2)?
- most common drainage pattern
- develops with rocks that resist erosion
What is a trellis drainage pattern (2)?
- dipping/folded topography
- variety of rocks with different rates of erosion
What is a radial drainage pattern?
develops when streams flow off of a central peak
What is a parallel drainage pattern (2)?
- associated with steep slope and high velocity streams
- more common in arid environments
What is a rectangular drainage pattern?
faulted/jointed landscape
What is a deranged drainage pattern?
glaciated landscapes
What are the three factors that create a fluvial landscape?
- stream gradient: the rate at which the stream’s elevation from the headwaters to the mouth declines
- base level: the level below which a stream cannot erode its valley
- stream discharge: the volume of water flowing in the stream past a certain location at a certain time
In what three ways do streams erode?
- headward erosion: headwaters erode upstream
- downcutting: material eroded from bottom of stream
- lateral erosion: side-to-side erosion
What is the difference between a graded and ungraded stream?
- ungraded stream: stream is actively eroding/depositing material
- graded stream: just enough energy to transport sediment; no erosion/depositon
What is the discharge formula?
Q = width x depth x velocity
What happens if stream discharge increases?
width, depth, and/or velocity increase
What are perennial streams (4)?
- always flowing
- more common in wetter environments
- fed by groundwater and surface runoff
- groundwater source allows stream to flow year-round
What are intermittent streams (3)?
- not always flowing
- flows only with precipitation
- mostly fed by surface runoff
What are ephemeral streams (3)?
- no water most of the time
- flow in immediate aftermath of precipitation
- fed by surface runoff only
What are exoitc streams (3)?
- stream that originates in wet environment and flows through dry environment
- high potential for evapotranspiration
- made worse by people diverting water for agriculture
What is hydraulic action (2)?
- water flowing through a stream channel squeezes and releases rocks
- slowly loosens and lifts rocks
What is abrasion (2)?
- rock particles grind and carve out stream bed as they are transported
- similar to sandpaper
What is the difference between turbulent and laminar flow?
- turbulent: water particles move randomly and cross paths in all directions
- laminar: water particles flwoing in the same direction (calm appearance)
What are the five factors of stream transportation?
- stream gradient
- rock type
- climate
- vegetation
- human activity
What is competence (2)?
- the ability of a stream to move particles of a certain size
- streams with higher velocity can transport larger particles; streams with lower velocity can transport smaller particles
What is capacity (2)?
- total amount of material that can be transported downstream
- higher capacity and competence result in brownish color
What are the three loads of stream transportation?
- solution load: materials that have been dissolved into the water
- suspended load: finer-grained material that remains suspended in the water
- bedload: consists of saltation (particles bouncing along the bottom of the stream) and traction (particles dragged along the stream bed)
What is aggradation (2)?
- the buildup of a stream channel through the process of deposition
- frequently occurs after flooding
What is alluvium (2)?
- any material deposited by running water
- generally deposited in floodplains, deltas, and stream beds
What is a braided channel (2)?
- deposition of alluvium in little islands in the stream
- typically in areas with glaciers
What is a meander (5)?
- stream moves laterally across valley floor
- gradient, velocity, and sediment flow remain steady
- point bar: experiences deposition
- cutbank: experiences erosion
- fast water on outside, slow water on inside
What is an oxbow lake (4)?
- a neck forms where a lengthening meander loops back on itself
- over time, the neck narrows as erosion undercuts the banks
- eventually, the stream erodes through the neck, forming a cutoff
- an oxbow lake forms as sediment fills the area between the new stream channel and its old meander
What is a nickpoint (3)?
- the profile of the stream experiences an abrupt change in gradient
- results in waterfalls and rapids
- occurs with rock resistant to erosion, tectonic uplift, and temporary blockages
What is a floodplain (3)?
- byproduct of many years of alluvial deposits
- higher land on either side
- flood occasionally
What are meander scars (2)?
- byproduct of shifting channel
- remnant of old stream channel
What is a backswamp (3)?
- low-lying land off the main channel of the stream
- water more likely to collect here
- results in swampy/boggy area
What is a yazoo stream?
tributary stream which runs parallel to main channel instead of joining it immediately
What is a levee (3)?
- earthen barrier on either side of a stream
- can be natural or man-made
- material is deposited on either side of stream after flooding
What are alluvial fans (2)?
- only form in dry environments
- ephemeral stream slows and expands after exiting canyon
What are river deltas (2)?
- form when stream exits confining channel
- rich soil, productive agriculture
