Rivers - Floods Flashcards
Flooding
where land that is normally not underwater becomes submerged
infiltration
Water sinking into the soil from the ground surface
discharge
amount of water than passes a given point on a stream or river bank within a given period of time
interception
water prevented from reaching the surface by trees and grass
physical causes
precipitation
- continuous heavy rainfall + prolonged light rainfall - saturates the soil (aka fills pores w/ water)
- sudden bursts/snow - (snow melts), infiltrates quickly, surface runoff increases, water will reach river quicker so the discharge increases
physical causes
geology
- impermeable rock - doesnt allow water to infiltrate = more surface runoff = increase in discharge
- permeable rock - allows water to infiltrate, so waters store = decrease chance of flood
physical causes
relief
- steep slopes - more likely for surface runoff bc water doesnt have time to infiltrate bc its going down = higher discharge
- flat + flood plains - lower risk bc water has time to infiltrate the soil
human causes
urban land use
- new infrastructure/new housing/disappearing gardens: increases area covered by impermeable surfaces = more surface runoff
- new housing: rainwater will flow into gutters and into drains, can be built in place w/ high flood risk
human causes
rural land use
- deforestation: reduces interception = saturated soil = increased runoff = increased discharge
- farming technique: removal of hedges, arable results in soil being bare
- urbanisation: greenfield sites getting built on
- climate change: extreme weather events, increased temp = more evap = more rainfall
effects
social
- Injury
- Death
- Loss of home
- Loss of belongings
- Damage to property
- Stressful
- Isolate – loss of roads
- Loss of recreational facilities
effects
economic
- Rebuild/fixing damage
- High insurance claims
- Loss of work/employment
- Loss of revenue for local area
- House value could decline
effects
enviornmental
- Habitats lost
- Loss of land
- Disrupts breeding areas
- Spread of pollution
- Spread of disease
- Large deposits of mud left behind
- Unsanitary conditions if sewage/grains flood
Flashy Response
when a drainage basin responds quickly
flashy hydrogaphy
basin size
small basins often lead to rapid water transfer
flashy hydrogaphy
drainage density
high density speeds up water transfer
flashy hydrographs
rock type
impermeable rocks helprapid overland flow
flashy hydrogaphy
land use
urbanisation = rapid water transfer
flashy hydrogaphy
relief
steep slopes = rapid water transfer
flashy hydrogaphy
soil moisture
saturated soil= rapid overland flow
flashy hydrogaphy
rainfall intensity
heavy rain may be more than vol that can be intercepted = rapid overland flow
flat hydrograph
basin size
large basin = slow water transfer
flat hydrograph
drainage density
low density = slow water transfer
flat hydrograph
rock type
permeable rock = slow water transfer bc it mves in groundwater flow
flat hydrograph
land use
forest = slower water transfer bc interception
flat hydrograph
relief
gentle slopes = slower water transfer
flat hydrograph
soil moisture
dry soil =slower water transfer
flat hydrograph
rainfall intensity
light rain = slower transfer
hard engineering
embankents
advantages
* cheap compared to hard engineering
* channel has more space
* used for riverside footpaths
* provide habitats for animals eg kingfishers and otters
disadvantages
* high maintance cost
* no easy access for boats and fishing
* false sense of security = not being prepped for floods
* concrete lining displaces animals
* ugly
* breached water cant get back into the river = water lying on ground for a while
hard engineering
flood relief channel
advantages
* artificial reed beds and grass-covered concrete sides = provide new habitats
* no flooding in a particular area
* footpaths & cycle tracks are built along channel, bird watching and nature reserves
* lower insurance costs
* value of homes increases = easier
disadvantages
* habitats disturbed
* ugly
* expensive + high maintance
* displacment
* some ppl protected at the expense of others
hard engineering
dams & reservoirs
advantages
* boosts tourism
* hydroelectric power
* area around used by forestry to plant trees = employment
* drinking water
* no flood risk
* new habitats
disadvantages
* relocation of ppl
* communities break up
* v expensive to build and mantain
* less fertile soil = less yield bc of lack of sediment deposited downstream
* algae builds up = deoxyginated water
* may trigger earthquakes/landslides
* floods areas of outstanding natural beauty = kills plants and animals
hard engineering
channel straightening
advantages
* protects places from flooding
* may prevent nesting sites from being lost
* moves water away more quickly = reduced flood risk
* straight course improves navig & increases trade opportuns
* insurance cost goes down = homeowners more likely to invest
disadvantages
* v expensive
* ugly
* problem not solved just moved away
* downstream floods effects animals
* fast flow in straight sections = deposition of silt elsewhere = floods
hard engineering
use of artificial structures to prevent or control natural processes
soft engineering
work with natural river processes to manage the flood risk
soft engineering
flood warning and prep
advantages
* cheap
* doesnt intefer with natural river
* ppl feel prepped & secure and can protect their stuff before = less impact
disadvantages
* some predictions may be wrong = unnecessary panic
* not everyone has access to media
* ppl actually have to do wht is said
* damage still occurs
* houses hard to sell
* distrupts habitats & ecosystems
* clear up is not good bc ppl forced into temp accom
soft engineering
floodplain zoning
advantages
* lots of uk cities on floodplains
* cheap
* permeable surfaces remain
* damage is less expensive bc only low value is effected
disadvantages
* limits development bc certain land cant be used
* harded to enforce and plain in LICs
* habitats on other greenfield sites are destroyed as development is forced elsewhere
soft engineering
planting trees
advantages
* co2 absorbed
* new habitat = increased biodiversity
* grants from government
* low maintance cost
* can be done in LICs bc of low skill involved
* reduces percipitation flooding bc interception
disadvantages
* large areas of land needed
* natural habitats changed from grass to trees
soft engineering
river restoration
advantages
* boosts tourism
* little maintance
* biodiversity increase
* pretty
* businesses not affected
* reduces flood risk
disadvantages
* initial cost high
* pssible damage to land nearby
