Hydrological Cycle Flashcards
What are the meteorological causes of flooding?
Much flooding in the UK is the result of mid-lattitude deopressions forming from low air pressure.
These usually bring showers on the warm from and rain on the cold front.
When rain is prolonged, the ground becomes saturated which causes more surface run-off
once the channel capacity is exceeded, water will break the banks and flow onto the floodplain
What are the physical causes of flooding?
- Flash floods
- Monsoons
- Rock type
- Soil saturation
- Tributaries
- Slope
- Snowmelt
What is flash flooding?
a flood with an exceptionally short lag time- often minutes or hours
What is groundwater flooding?
flooding that occurs after the ground has become saturated from prolonged heavy rainfall
What is surface water flooding?
flooding that occurs when intense rainfall has insufficent time to infiltrate the soil, so flows overland
What is resistance time?
the amount of time a particle stays in a store
What is flow rate?
speed at which a particle moves from one store to another
CASE STUDY
What are some key fact of the 2015 Storm Desmond?
- 6ft of water
- Roads washed away and buldings submerged
- Army dropped off water and nearby villiages bought food
- Flood defences were built after the 2009 flood but the didnt work
CASE STUDY
What are some of the social consequences of Storm Desmond?
- 5200 homes flooded
- 20,000 people had to live in temporary accomodation
- Local services were forced to close
CASE STUDY
What are some of the environmental consequences of Storm Desmond?
- Rivers polluted with sewage
- Many riverbanks were eroded, adding to future flood risks
CASE STUDY
What are some of the economic consequences of Storm Desmond?
- The cost of the damage was £450m
- Insurance claims by flooding across the UK were £6bn in 2015
What are the human causes of flooding?
- Channel straightening
- Building on floodplains
- Impermeable ground
- Dams built to supply towns with water
- Streams channeled into culverts to aid rapid drainage of farmland
- Grazing animals trample soil
- Plouging compacts soil
- Dredging rivers
- Deforestation
CASE STUDY
What are some key facts of the Boscastle 2004 flood?
- Helicopters worked for 3hres, rescuing 120 people
£250,000 in damage - River level had risen by 7ft in one hour
- The villiage was built on a floodplain
- 2 million tons of water flower through
- Saturation of bedrock from previous rain resulted in the sandstone behaving as if it was impermeable
What is a drought?
An extended period- a season, a year or several years- of deficient rainfall relative to the statistical malti-year average
What is a meteorological drought?
Happens where long-term precipitation is lower than normal. It changes for different regions as it is affected by the atmspheric conditions
What is an agricultural drought?
Happens when there is not enough soil moisture to allow enough crops to grow. It is caused by precipotation shortages, changes in rates of evapotranspiration and reduced groundwater levels
What is a hydrological drought?
Happens when the amount of surface and surface water is defficient. It is caused by a lack of precipitation and usually occurs after meteorological and agricultural drought
What is a socio-economic drought?
Occurs when water demand outstrips the water avaliability. This could be caused by a lock of precipitation or by human overuse of sources of water
What is the best indicator of drought and how does it work?
Palmer drought severity index. The higher the number the less severe it is
What is ecosystem resilience?
The ability of an ecosystem to respond to a disruption of normal function and recover quickly
CASE STUDY: California (drought)
What are the human contributions of drought?
- Population of 40 million meaning that there are human pressures on water supplies
- Climate change
- Huge industry of agriculture meaning that there is high demand for irrigation
CASE STUDY: California (drought)
What are the physical contributions of drought?
- Has mountains which affect rainfall
- Towards the eastern border is the Arizonian Desert
CASE STUDY: California (drought)
What is the evidence for the drought?
- 2007- Californian fires were due to the Santa Ana winds blowing out from the Great Plains
- 2007- was set to become the driest year on record- only 25% average rainfall
CASE STUDY: Horn of Africa
What are the human contributions of drought?
- Deforestation
- Overgrazing
- Urbanisation
- Climate change
- Lack of disaster resilience
CASE STUDY: Horn of Africa
What are the physical contributions of drought?
Changing weather patterns
Lack of rainfall
CASE STUDY: Horn of Africa
What is the evidence for the drought?
- 5 years of low rainfall
- 2006- 3 months of intense rainfall
- Population double in previous 30 years- expected to increase by 40% by 2059
- 85,000 people evacuated due to transport links
What are some of the causes of flooding?
- Long or heavy periods of rainfall
- Impermeable soil & rock
- Saturated soils
why are wetlands important ecosystems?
- Mitigate against flood risk
- Recharge aquifers
- High biological productivity
- Protect land from erosion
- Act like water filters
- Provide fish and fuelwood
Why are forests important ecosystems?
- Second largest store of carbon
- 2 billion people rely on forests for food, medicine, firewood, etc
- TRFs produce 28% of oxygen
- Provide food, shelter, and fuel
- Home to 80% of terrestrial biodiversity
What are the ways drought can affect wetlands?
- water availability- water table lowers and dries out wetlands
- water quality- water=more concentrated=decreases water quality
- Habitat loss- species forced to migrate
- Altered nutrient cycling- reduction in water flow=lower exchange of nutrients with surrounding areas
What are the ways that drought can affect forests?
- Reduced soil moisture- plants cant obtain water
- Increased fire risk- dry conditions=easier for forest fires to start and spread
- Altered tree growth- slows down
- Changing in species composition- species cannot adapt and could face extinction
- Impact on wildlife- species may experience a change in distribution
High pressure
when air sinks- has drier conditions
Low pressure
when air rises- has wetter conditions
What is a ‘normal year’?
there are droughts in South America and floods in Australia
What is a ‘La Nina year’?
an enhanced ‘normal year’
What is an ‘El Nino year’?
there are floods in South America and droughts in Australia
What percentage of the earth is water?
70%
Transpiration
Evaporation that occurs off of leaves
Percolation
Waters moving down due to gravity through rocks beneath (slowly)
Surface run off
Water flowing along an impermeable surface