Theme 2 Chapter 2 - Rivers Flashcards
Name the stores and flows in the hydrological cycle?
STORES:
- Ground store
- Vegetation store
- River store
- Sea/ocean store
- cloud store
FLOWS:
- Evapotranspiration
- Infiltration
- Groundwater flow
- Evaporation
- Precipitation
- Condensation
- Through flow
- Percolation
- Surface flow
Features of a river and their definitions?
Source: where the river starts - usually in mountains
Meander: bend in a river
Tributaries: smaller rivers branching of the main river
Confluence: where two rivers meet
Mouth: where the river ends at sea
4 types of transportation:
Solution: Minerals from rocks dissolve in water
Suspension: small materials easily carried by stream
Saltation: larger materials bounce along river bed
Traction: largest materials dragged along river bed
How are meanders formed?
The inside bend of the river:
- Low amounts of energy
- Slower water flow
- Decomposition occurs
- Shallower waters
- Slip off slope are formed
The outside bend of a river:
- High amounts of energy
- Faster water flow
- Erosion
- Deeper waters
- River cliff formed
How are Oxbow lakes formed?
1) Over time necks of meander becomes narrower as meander erodes
2) Eventually, ,meanders join up and water travels straight across
3) River deposits sediment and seals loop
4) Outer part of loop left isolated and horseshoe shaped lake formed (Oxbow lake)
How are waterfalls and gorges formed?
1) Only occurs when there is hard rock over soft rock
2) Erosion of soft rock undercuts the cliff forming a plunge pool
3) Overhanging cliff collapses into the plunge pool due to gravity
4) Overtime waterfall becomes taller and retreats
How are floodplains and levees formed?
1) When a river floods the banks overflow
2) Smaller materials brought up by floods are carried further while larger materials are deposited on embankments as they lose energy/ speed
3) A fertile and flat floodplain is created which acts as a natural barrier against floods
What is the long profile of a river?
Upper river:
- fast water flow
- lots of erosion
- Traction
- Water falls and gorges
- River narrow and shallow
Middle river:
- Lots of erosion on outside bend and decomposition on inside bend
- Saltation and suspension
- Meanders and Oxbow lakes
- River is wider
Lower river:
- Slow flowing water
- Decomposition
- Levees
- River widest and deepest
Physical factors contributing to flooding:
- Impermeable bedrock
- Steep valley slopes
- Saturated soil
- Frozen ground
- Heavy rainfall
- Rapid snow melt (sunny)
Human factors contributing to flooding:
- Deforestation
- Covering floodplains with impermeable surfaces like concrete
- overgrazing
- Rapid snow melt (global warming)
How does the physical factors affect flooding (this means…)?
- Heavy rain: more volume of water in river
- Steep valley slopes: faster surface run off into rivers
- Frozen ground: Land becomes impermeable, more surface flow and less infiltration
- Impermeable bedrock: less percolation, Ground store more saturated, water sits on surface, more surface flow
- Rapid snow melt: more water entering river rapidly
How do the human factors affect flooding (this means…)?
- Deforestation: less tree roots absorbing river water and less trees acting as barrier for river water
- Impermeable surfaces on floodplain: less infiltration, more surface flow
- Overgrazing: Soil saturated with water easily, water sits on surface and more surface flow into rivers
Hard engineering methods for rivers and their definitions?
Dam: Concrete barrier which controls the flow of water
Artificial levees: structures that give further height to embankments
Straightening meander: Altering river channel so it runs straight to sea
Deepening riverbed: Dredging river channel to make it deeper
Demountable barriers: Electronically devised barriers that rise during times of flood
Soft engineering methods for rivers and their definitions?
Afforestation: Replanting trees close to river channel
Warning system: Accurate flood warming to inform locals of flood
Zoning: Local counsels make plans on how land is used on floodplain
Flood plan: Governments give tips and advise on protection of houses against floods
Advantages and disadvantages of hard engineering methods?
Dam:
ADV: effective
DISADV: expensive
Artificial levees:
ADV: River discharge has more room to move upwards
DISADV: Block view of rivers
Straightening meanders:
ADV: effective getting river water rapidly out to sea
DISADV: may have to displace locals out the area
Dredging river:
ADV: River discharge has more room to move upwards
DISADV: Noise pollution/ disturbance
Demountable barriers:
ADV: Doesn’t require man power
DISADV: Only protects specialised areas
