River Systems (Theme6) Flashcards
What is the normal sequence of processes in landscape development?
Weathering, erosion, transport, deposition
What are the forces of river weathering & erosion?
- Hydraulic action
- Abrasion
- Attrition
- Solution (chem erosion)
What are the 2 factors contributing to the transportation of river particles?
Size
Velocity
What are the 4 types of transportation?
- Solution
- Suspension
- Saltation (sautation)
- Traction (river bottom)
Where are river energy levels the lowest?
Where lakes or seas meet with rivers
What type of land forms when deposition occurs?
River deltas
What does the long profile of a river describe?
Source to mouth - rivers are cutting route and flattening down towards mouth
What does water balance equation say?
Water inputs = water outputs + change in storage
What 2 types of events contribute to the precipitation in the water cycle?
-Extreme events
-low magnitude events
What is a drainage divide?
High point separating one or more drainage basins. Can be a point or a line
How is stream order classified?
1st, 2nd, nth order streams depending on if they are closer to the source or the mouth. Stream order increases where 2 or more streams become confluent.
What are the 3 types of stream?
Intermittent stream (dry during parts of the year)
Permanent streams
Ephemeral streams (flow briefly for a few hours after extreme rainfall events)
What are the 4 drainage patterns? Describe each.
Dendritic - branches
Trellis - develops in linear mountain valleys (product of anticline & syncline folded rock structures - erosivity impacts drainage shape)
Rectangular - Joints/cracks in landscape directs water in right angles
Radial - water flowing from central dome/peak (volcano)
What 2 factors is stream discharge (Q) dependent on ?
-Climate
-Resisting framework (shape, geology)
What is it called when the entire river channel is filled? What is the consequence of this?
Bankfull discharge = maximum force = maximum erosion
What causes a knickpoint?
More resistant strata with less resistant (more erosive) strata underneath.
Can nickpoints move over time?
Yes. They move upstream with the erosion of less resistant strata under riverbed.
What are the 4 different types of river channel?
Straight (sinuosity < 1.3)
Meandering ( sin. > 1.5)
Braided (unvegetated bars)
Anastomosing/Anabranching (vegetated islands)
Along the longitudinal profile, how does channel gradient change?
Decreases
Along the longitudinal profile, how does discharge change?
Increases
Along the longitudinal profile, how does Velocity change?
Decreases
Along the longitudinal profile, how does cross-sectional area change?
Increases
What is Lane’s stable channel balance
sediment load vs discharge.
Incision vs Aggradation
What is the line of fastest/strongest flow called?
Thalweg. Outside lines of each curve.
What does the curving of a river in a floodplain lead to?
erosion of outer bank
formation of point bars (inner banks)
meandering cut off -> oxbow lakes
What do you call an abandoned floodplain?
A terrace
What type of river planiform is this?
Meandering. Sinuosity > 1.5
What type of river planiform is this?
Braided. Notice: unvegetated bars
What type of river planiform is this?
Anastomosing. Notice: vegetated islands
What is Lane’s Stable Channel Balance?
fundamental controls of river forms. Sediment load, discharge, sediment size, stream slope, etc.
What process occurs when rivers are slow and flat?
aggradation. deposition of sediment
What process occurs when rivers are fast and steep?
Incision. Processes of erosion + transport
What are the two types of sediment sorting that can occur in deposition?
Horizontal and vertical sorting.
What are 3 main types of delta?
Arcuate delta
Cuspate delta
Bird’s foot delta
What 4 variables control delta morphology?
- Sediment Load.
- Discharge
- Wave energy
- Tidal range
