12 - Glacial landscapes

• Hard engineering


  Uses heavy machinery to build artificial structures which work against nature to reduce the risk of flooding
• Dams and reservoirs


  A dam is a large concrete barrier built across a river to impede its flow, causing the valley behind to flood and form an artificial lake called a reservoir
• Dams and reservoirs


  • Highly effective against floods - release of water is highly controlled so there is virtually no risk of flooding
  • Forestry - areas around reservoirs may be planted with forests
  • Source of drinking water - the reservoir holds a large volume of water to supply drinking water
  • Promotes new habitats - these develop in and around a reservoir
  • Boosts tourism - reservoirs are attractive
  • Provides hydroelectric power - turbines may be placed in a dam
• Kielder Dam and Reservoir in Northumberland was completed in 1981
• Costs of dams and reservoirs

  • Social costs: Flooding of a valley displaces people, usually farmers from their homes
  • Economic costs: Dams are expensive, loss of industry meant less demand than expected
  • Environmental costs: Interferes with migrating fish, algae collects behind dam, triggers earthquakes, floods areas of outstanding natural beauty
• Channel straightening


  When a meandering section of a river is engineered to create a widened, straightened and deepened course to improve boat navigation and reduce flood risk
• Benefits of channel straightening

  • Reduces flood risk by moving water out of the area more quickly
  • Improved navigation and increased trade at ports
• Costs of channel straightening

  • Water flows through straightened section quickly but slows down downstream, causing sedimentation and flooding
  • Expensive to dredge downstream sedimentation
  • Changes in hydrology and flooding endanger animals and destroy habitats
• Embankments


  Artificially raised river banks to contain more water in the channel and reduce flood risk
• Benefits of embankments


  • Safer from flooding - increased carrying capacity of channel
  • Cheap to build compared to other hard engineering
  • Provide habitats for riverbank animals
  • Used for riverside footpaths
• Costs of embankments


  • Deprive people of easy access to river
  • Not as reliable as other hard engineering, give false sense of security
  • Higher maintenance costs, prone to erosion
  • Displace riverbank animals from habitats
• Flood relief channels


  Artificially made channels designed as a backup to divert excess water from a river that frequently floods
• Benefits of flood relief channels


  • Remove risk of flooding from designated area
  • Provide areas for recreation like footpaths, cycle tracks, model boating
  • Lower insurance costs and increase property values in vicinity
• Costs of flood relief channels

  • Disrupt people living in path of channel
  • Increase flooding downstream as water merges
  • Expensive to build and maintain
  • Disturb habitats during construction, provide unreliable habitats
• Soft engineering


  Adapting to a river and learning to live with it, often cheaper but less effective than hard engineering
• Soft engineering methods


  • Flood plain zoning
  • Flood warnings and preparation
  • Planting trees
  • River restoration
• Trees and river restoration
• Flood plain zones


  • Zone 3b
  • Zone 3a
  • Zone 2
  • Zone 1
• Flood plain zoning


  Where land in a river valley is used in such a way as to minimise the impact of flooding
• The Environment Agency (EA) categorises land into four flood-risk zones and issues flood risk maps
• Local authorities are required to use these maps to produce flood-risk assessments and to guide decisions regarding new building applications
• How flood warnings and preparation work

  1. The EA and other agencies co-ordinate efforts to devise and carry out action plans

  2. The meteorological office analyses data and passes it to the EA

  3. The EA provides updated flood alert information, a flood map website, a three-day flood forecast, and personalised warnings

  4. The EA provides information on how to prepare for a flood
• Planting trees


  Reduces water flowing downstream as shelter belts of broad-leaf trees can reduce surface runoff
• River restoration


  When a river that has previously been hard engineered is restored to a natural channel
• Benefits of flood plain zoning

  • Restricting building on the active flood plain reduces risk of flooding
  • Low-cost: only administration costs
  • Protects traditional water meadows
  • Provides green space in towns
• Costs of flood plain zoning

  • Limited impact as many cities have already sprawled over the flood plain
  • Difficult to get planning permission to extend/rebuild in flood plain
  • Housing shortage worsens, restricted supply inflates house prices
  • Habitats destroyed due to increased building on other greenfield sites
• Benefits of flood warnings and preparation

  • Cheap way of protecting people and property
  • Allows people to protect valuables earlier
  • Ensures safety without high-cost hard engineering
• Costs of flood warnings and preparation


  • Only effective if people listen and take action
  • Does not prevent flooding
  • Distressing clear-up operation, increased insurance costs
• Benefits of planting trees

  • Reduces water flow downstream
  • Absorbs more carbon dioxide
  • Adds variety and habitats, increases biodiversity
• Costs of planting trees

  • Changed appearance, less aesthetically pleasing
  • Loss of potential grazing land
• Benefits of river restoration

  • Creates new wetland habitats and increases biodiversity
  • Increased water storage reduces downstream flood risk
  • Aesthetically pleasing, increases visitor numbers
• Costs of river restoration

  • Possible loss of agricultural land and flooded crops
  • Can be expensive, initial cost of £1.1 million for River Quaggy
• The Jubilee River is a relief channel for the River Thames in South East England
• Jubilee River


  • 11.7 kilometres long, 50 metres wide, UK's largest artificial channel
  • Designed to look like a natural river with meanders and shallow reed beds
  • Has five weirs, only two are navigable by paddle craft
  • Diverts water from the River Thames to prevent it overflowing its banks, reducing flood risk in southeast Maidenhead, Eton and Windsor
• The Jubilee River scheme was funded by the Environment Agency and cost £110 million
• Social issues with the Jubilee River scheme

  • Protecting some properties at expense of others
  • Paddle boaters promised navigable river but have to carry boats around weirs
• Economic issues with the Jubilee River scheme

  • Most expensive flood-relief scheme in UK
  • Weirs damaged by floods, £680,000 repair bill
  • Maintaining the channel is a huge economic burden
  • Unfair that Windsor and Eton residents didn't have to pay
  • Businesses lose money when flooded, high insurance costs
• Environmental issues with the Jubilee River scheme

  • Extensive flooding downstream where channel rejoins Thames
  • Concrete weirs are ugly, algae disrupts ecosystem
  • Habitats disturbed by flooding
• Plucking


  As the ice moves over the rock surface below, meltwater freezes around loose sections, pulling them away
• Plucking is especially effective when the rock contains many joints (cracks) which the water can seep into</b>