3 River Landscapes Flashcards Preview

GCSE Geography > 3 River Landscapes > Flashcards

Flashcards in 3 River Landscapes Deck (20):

Why is deposited material called sediment? (3)

- Drier weather (less water = less energy)
- River slows in speed (e.g. inside bend)
- River floods (water on to the floodplain and deposits layers of fine silt and clay [alluvium] which is fertile = good for farming)


Explain the formation of meanders to ox-bow lakes.

- Water flows fastest on the outer bend and wears away the river
- The water undercuts the bank (slowest flow on the inner bend)
- Meander becomes exaggerated
- Sediment is deposited in the inner bend and erosion continues on the outer bend
- Meander neck narrows as processes go on
- River cuts through the neck at a time of high discharge
- River floods so it takes the easiest route forming an ox-bow lake


Properties of the upper course.

Gradient: steep
Valley: V-shaped
Processes: vertical erosion
Landforms: interlocking spurs, rapids, mountains, source
Discharge: low
Velocity: high
Load: large angular boulders, large bedload


Properties of the middle course

Gradient: gentle
Valley: U-shaped, deep/wide flat floor
Processes: deposition, lateral erosion, transportation
Landforms: meander, floodplain
Load: smaller material in load


Properties of the lower course

Gradient: very gentle
Valley: wide and deep
Processes: mostly deposition, lateral erosion
Landforms: levees, estuaries, mouth, meanders
Discharge: high
Velocity: low
Load: suspended load, large sediment load


Explain to formation of interlocking spurs

Stage 1: in the upper course of a river, most of the erosion is vertical. This creates a steep-sided, V-shaped valley.
Stage 2: the rivers aren’t powerful enough to erode laterally so they have to wind around the high hillsides that stick out into their paths on either side.
Stage 3: most of the energy is being used to overcome friction and the left over energy is used in hydraulic action to deepen the channel. The obstacles of harder rock from the high hillsides are hard to break through so the river takes the easiest route over land or around the hard rock and through the soft rock.
Stage 4: projections of high land entering the valley from alternative side = interlocking spurs.


Explain the formation of waterfalls into gorges.

- Waterfalls form where a river flows over an area of hard rock overlaying soft rock.
- The softer rock is eroded (hydraulic action & abrasion) more than the hard rock creating a ‘step’ in the river.
- As water flows over the softer rock, it continuously eroded the soft rock creating a steep drop - waterfall
- The erosion of the soft rock continues reaching the rock underneath the hard rock and eventually wearing it away.
- This leaves the overhanging hard rock with no support (a notch) so it collapses and the rock builds up at the bottom of the river.
- This rock adds to the process of abrasion creating a deeper pool (plunge pool).
- The undercutting of the soft rock below the hard rock repeats and continues overtime causing the waterfall to retreat and form a steep-sided gorge.


Advantages and disadvantages of flood relief channels (3) H

+ Discharge reduced
+ Release of water controlled
- Increased discharge at the end of the channel


Advantages and disadvantages of dams and reservoirs (3) H

+ Reservoirs store water and reduce the risk of flooding over long periods
+ River flow controlled
- Very expensive


Advantages and disadvantages of channel straightening (2) H

+ Water moves out area quicker
- Flooding may occurs downstream


Advantages and disadvantages of embankments (2) H

+ Hold more water
- Expensive


Advantages and disadvantages of planting trees (3) S

+ Increase interception and lag time
+ Risk and discharge reduced
- Less land available for farming


Advantages and disadvantages of river restoration (3) S

+ Discharge reduced
+ Risk reduced
- Local flood risk can increase


Advantages and disadvantages of flood plain zoning (2) S

+ Risk reduced
- Expansion of urban areas are reduced


Advantages and disadvantages of flood warnings (3) S

+ Impact reduced
- Doesn’t stop the flood
- People may not have access to the warnings


Advantages and disadvantages of preparation (2) S

+ Impact reduced
- Doesn’t guarantee safety


Features of river hydrographs (7)

- Bar graph (rainfall shown in mm)
- Line graph (discharge in m3/s)
- Base flow/groundwater level (normal discharge of river)
- Rising limb (rising flow in the river)
- Falling limb (falling floodwater in the river)
- Peak discharge/flow (maximum discharge in the river)
- Lag time (time difference between peak rainfall and peak river flow)


Processes of the hydrological cycle (7)

- Precipitation (any moisture that falls from the atmosphere)
- Surface run-off (any water that hasn’t been percolated runs off the mountain due to gravity)
- Transpiration (evaporation from trees and plants [interception])
- Percolation (any water that enters the ground)
- Groundwater flow (amount of absorbed water underground)
- Evaporation
- Condensation


Types of erosion (4)

Abrasion, attrition, hydraulic action and solution.


Types of transportation (4)

Saltation, traction, solution and suspension.