2.2 Rivers Flashcards
The hydrological cycle:
- Drainage basin: the area of land drained by a river
- Watershed: the edge of highland surrounding a
drainage basin, marking the boundary between two
drainage basins - Source: the beginning or start of a river
- Confluence: the point at which two rivers or streams
join - Tributary: a stream/smaller river which joins a larger
stream or river - Mouth: point where river comes to end, usually when
entering sea
River processes:
Drainage basins act as a system with:
- Inputs: precipitation
- Transfers: infiltration, percolation, surface runoff,
throughflow & groundwater flow
- Stores: interception, surface storage, soil moisture
storage & groundwater storage
- Outputs: evaporation & transpiration or
evapotranspiration
Characteristics of the River:
- Bed
- Bank
- Width
- Depth
- Speed of flow
- Wetted perimeter
- Channel
- Thalweg
Purpose of river characteristics:
- Bed: The bottom of the river channel
- Bank: The sides of the river channel
- A river has two banks - Width: The distance between the two banks of a river
- Depth: The distance from the water surface to the bed
of a river - Speed of flow: how fast the water in a river is moving;
different speeds arise at different parts
of the river - Wetted perimeter: length of bed and banks in contact
with river - Channel: The route course (between bed and banks)
that a river flows. The flow of the river is
often described as channel flow. - Thalweg: The fastest part of the river, always near the
middle of the river channel, where there is
least friction
Erosion stages:
- Attrition
- Hydraullic Action
- Abrasion
- Solution
Erosion:
- Attrition: large particles such as boulders collide and
break into smaller pieces; occurs at higher part of river - Hydraulic action: the sheer force of the river dislodges
particles from its banks and bed - Abrasion: smaller particles rub against the river banks
and bed like sand-paper; occurs at low part of river - Solution: acid in rivers dissolve rocks; occurs at any
part of river
Transportation stages:
- Traction
- Saltation
- Suspension
- Solution
Transportation:
- Traction: rolling stones along the bed
- Saltation: small particles bounce along bed in a
leapfrog motion - Suspension: silt and clay-sized are carried within the
water flow - Solution: minerals dissolve in the water
Deposition:
- When a river lacks the energy to carry its load; it begins
depositing the heaviest particles - Happens when there is less water or where the current
slows down - Large boulders are deposited at the top, and very small
particles are deposited at the end, resulting in sorting
River profiles:
Upper
Middle
Lower
Upper (of river profile):
- long profile
- cross profile
Long profile:
Steeply sloping towards the lower sections of the river
Cross profile:
Steep sided v-shaped valley, thin river channel, deep in places
Middle (of river profile):
- long profile
- cross profile
Long profile:
Shallow slopes towards the mouth of the river
Cross profile:
V-shaped valley remains with a wider valley floor, river begins to meander, channel is wider and deeper
Lower (of river profile)
- long profile
- cross profile
Long profile:
Almost at sea level, gently sloping to its mouth
Cross profile:
Wide, shallow valley, with large flood plains and meanders; channel is wide deep and smooth sided.
Landforms:
- V-shaped valley
- Potholes
- Meanders
- Waterfalls
- Ox-bow lakes
- Levees
- Deltas
- Flood plain
V-shaped valley:
(landforms)
- Is narrow with a narrow, shallow river channel
- Has steep sides
- Channel has a steep gradient
- Water is mainly slow flowing
- Load is mainly large, angular and rough
