managing floods Flashcards
What is hard engineering?
using artificial structures to prevent/control natural processes from taking place
(preferred for protecting expensive property/land)
disadvantages
-expensive
-harmful impacts to environment
-social/aesthetic impacts
advantages
-economic savings -improvements to environment
-opportunities for leisure/recreation
what causes flooding
physical
- precipitation
- geology
- relief
human
- urbanisation
- deforestation
- agriculture
Dams/reservoirs
-regulates river flow/reduce risk of flooding
-multipurpose:
flood prevention
irrigation
water supply
hydroelectric power
recreation
-during high periods of rainfall, water can be stored in the reservoir, released when rainfall is low
-expensive
- construction is controversial
-reservoir often floods land
-people may have to be removed from their homes
Channel straightening
-cutting through meanders
-speeds up the flow
-may increase flood risk downstream
-smooth concrete lines the channel which speeds up flow/prevent collapsing river banks
-artificialness can reduce aquatic habitats/biodiversity
- unattractive
flood relief channels
-bypass urban areas
-At high flow times, sluice gates open to allow excess water to flow into the flood relief channel
-reduces amount of water flowing along the main river
-supportive of biodiversity
- provide leisure/recreation
-land use change can affect local community access to roads/footpaths and lose farmers’ land.
embankments
-raised river bank that allows river channel to hold more water before floods
-relatively cheap- constructed of mud dredged from river channel
-look like natural levees when covered by vegetation
-hard-engineering structures like concrete/stone can be used in cities where high/value property needs protection
-although effective, they are costly, obscure views of river, reduce biodiversity
What is soft engineering?
-working with the natural river processes to manage flood risk
-does not involve artificial structures/trying to stop natural processes
-reduces/slows movement of water into river channel to prevent flooding
-has costs/benefits
Flood warnings and preparation
-rivers are monitored using satellites/computer tech
-instruments used to measure rainfall/river levels
-computers predict discharges and identify areas at risk of flooding
-flood warnings of different levels issued
-environment agency makes maps identifying areas at risk where people can prepare
e.g. moving valuables, using flood gates/sandbags
-local authorities/emergency services use maps to plan responses to floods e.g. flood barriers, evacuation, road closures, securing buildings/services
-computer warnings effective if perceived by the public to be accurate
may blight areas, causing land/property prices to fall and insurance premiums to rise
floodplain zoning
-restricts different land uses to certain locations on the floodplain
e.g. areas close to river kept clear of high-value properties, instead used for pasture, parkland, playing fields
-cost effective
-hard to apply to already developed towns/cities
-may blight areas, causing land/property prices to fall
planting trees
-afforestation
-trees intercept rainfall, slowing transfer of water to river channels
-relatively cheap
-increases biodiversity
river restoration
-where the course of the river was artificially changed, river restoration can bring it back to its original course
-uses natural processes and features of a river: meanders, river-bank vegetation, wetlands
-this slows down river flow
-relatively cheap
-short term negative environmental impacts
-long term positive environmental impacts
-increased biodiversity
wetlands and flood storage areas
- wetlands deliberately allowed to flood, forming storage areas
- reduces risk of flooding downstream
Banbury
- 50km North of Oxford
- pop. of 45000
banbury has a history of flooding- 1998, 2007
- raised A361 stays open to avoid disruption
- scheme cost £18.5 million
- over 400 houses and 70 businesses protected for £100 mil
- new habitat created
