River processes and pressures Flashcards
What are the main features of a drainage basin ?
WATERSHED : highland that seperates drainage basins
CONFLUENCE : where two rivers meet
TIBUTARY : smaller stream that joins bigger stream
SOURCE : starting point of a stream
MOUTH : where stream joins sea
How are interlocking spurs created ?
- source of rivers have less power so flow around hard rock
- makes them bend around rock and for interlocking spurs
What are the features of meanders ?
- river gains more energy at middle course
- as river flows over flatter land, meander forms
- speed and erosion increases on outside of bend
- deposition on inside
How are ox-bow lakes formed ?
- meanders get closer due to erosion
- makes neck of lake narrower
- high discharge = river will take shortest route and erode neck
- makes straighter course
- gradual deposition cuts of meander
How are levees formed ?
- occur in lower course
- when river flood it loses energy
- largest materials deposited first
- smaller materials further away
- sediment build up to form levee
What are the features of a flood plain ?
- land that gets covered when river flood
- interlocking spurs are removed
- overtime height increases due to increased deposition
- often agriculture land
What are deltas and how are they formed ?
- found at mouth
- forms from sediment deposited by river as it enters slower moving water
How does the profile of a river change ?
U : steep, narrow shallow channel, steep sides
M : medium, wider deeper channel, gently sloping sides
L : gentle, very wide deep channel, very wide (almost flat) valley
Why is the flood risk in the UK rising ?
- increased population = more housing on flood plains
- urban development = more impermeable surfaces = increased surface run off
- change in weather patterns = more storms (from every 100yrs to 80yrs)
How does the EA manage flood risks ?
- invested £2.8bn
- manages river and land use
- building flood defences
- gives warning / helps people prepare
How is flooding reduced through CMP’s ?
- reduce run off by improving land use
- improve flood defences
- prevent insuitable development on flood plains
What are the advantages to hard engineering ?
EMBANKMENTS : stop overflowing, blend with environment
FLOOD WALLS : prevent water spreading in high impacts areas
DEMOUNTABLE FLOOD BARRIERS : put up and taken down, replace ugly permanent defences
STORM SURGE BARRIERS : protect large areas
What are the disadvantages of hard engineering ?
EMBANKMENTS : can burst under high pressure
FLOOD WALLS : expensive, cause flooding downstream, look unnatural
DFB : risk of timing issues
STORM SURGE BARRIERS : high construction costs, regular maintenance
What are the advantages of soft engineering ?
RIVER RESTORATION : more attractive, creates habitats
FLOOD PLAIN RETENTION : low risk areas used for building, high risk used for parks
What are the disadvantages of soft engineering ?
RIVER RESTORATION : some flood bank often still needed
FLOOD PLAIN RETENTION : poor public accessibility in some areas
