Chapter 12: Running Water (Streams) Flashcards
1
Q
Hydrologic Cycle
A
closed system
- Reservoirs
- Transfers
- Residence Time
2
Q
Residence Time
A
Average time a substance spends in a reservoir; calculated by dividing the amount in the reservoir by the rate of its addition
3
Q
Streams
A
Water in permanent channels; carry water and sediment to ocean; controlled by:
- water
- sediment load
- base level
4
Q
Stream discharge(m3/sec)
A
velocity x channel cross-sectional area Q=vA, where A=wd
5
Q
Infiltration and groundwater flow
A
- Base flow and perenial streams (humid)
- Ephemeral(impermanent) streams (dry)
6
Q
Sheet flow
A
infiltration capacity is exceeded
7
Q
Sediment load
A
Comes from mass wasting, sheet flow, stream erosion, and base flow
8
Q
Base level
A
lowest level to which a stream flows
- ultimate or local
- Drainage Basin: area drained by a stream
- Longitudinal profile: graded stream gradient (rise/run)
9
Q
Channel Depth
A
- Downcutting erosion (channel deepening)
- Channel filling or deposition
10
Q
Channel Width
A
- Lateral Erosion: cut bank, outside a bend
- Lateral Accretion (deposition) of bed load sediment: point bar deposit, inside of bend
- Meander migration and flood plain formation
11
Q
Meander Migration
A
- Mud from floods: vertical accretion (deposition) of suspend-load sediment
- Formation of stream terraces: flood plains abandoned by down cutting
12
Q
Channel pattern and shape
A
- Meandering: suspend-load channel, cohesive sediment, deep and narrow, gentler gradient, common esp. in humid regions
- Braided: bed-load channel, non-cohesive sediment, wide, shallow, steeper gradient, where valley is “sediment-choked” in front of glacier and in arid regions
13
Q
Gradient
A
- Headward Erosion: can result when lowered base level causes increased gradient
- Floodplain mud depostion results from decreased gradient (so do alluvial fans and deltas)
