11 - River landscapes

• Hard engineering


  Works against nature, generally more expensive but more effective
• Soft engineering


  Works more in sympathy with nature, generally less expensive but less effective
• Beach nourishment


  1. Replacement of lost sediment

  2. Sediment taken from a bay and placed on a beach losing sand

  3. Sediment removed from a down-drift area and returned up-drift
• Beach reprofiling


  Artificial re-shaping of a beach using existing beach material
• Sand dune regeneration


  Artificial creation of new sand dunes or restoration of existing dunes
• Benefits of beach nourishment

  • Wider beach means more room for beach users
  • People living along seafront more protected from coastal flooding
  • Wider beach protects expensive properties
  • Wider beach may attract more tourists
  • Nourished beach is natural and blends in with environment
• Costs of beach nourishment

  • Access to beach restricted during re-nourishment
  • Beach recycling may cause resentment from residents near donor area
  • High overheads to hire dredger, £1.95 million for 137,000 m3 at Sandbanks
• Benefits of beach reprofiling

  • Residential area behind beach now protected so residents feel safe
  • Prevents breach, protects Pevensey Levels, beach still looks reasonably natural
• Costs of beach reprofiling

  • Bulldozers restrict beach access, especially in winter
  • Major reprofiling costs can be expensive, £200,000 per year at Selsey
  • Steep, high-crested beach may look unnatural and uninviting to tourists
• Benefits of sand dune regeneration

  • Sand dunes protect land uses behind them
  • Established dunes popular for picnics and walking
  • Small planting projects use volunteer labour and local grass, so costs minimal
  • Helps maintain habitat for rare species
• Costs of sand dune regeneration

  • Regenerated dunes fenced off and signed to keep out, may deter tourists
  • Dune regeneration needs twice yearly checks and fertiliser application
  • Expensive systems needed to protect planted areas from trampling
  • No guarantee regenerated dunes will be stable, may need additional engineering
• Coastal realignment


  Creating an engineered new position of a coastline, involves moving the boundary inland
• Managed retreat


  Decision to no longer follow 'hold the line' strategy, people moved out, buildings demolished, breach made in existing defences to allow sea inundation and create new intertidal habitats
• Coastal realignment offers a sustainable long-term solution to rising sea levels, better to manage planned inundation than react to breaches
• Benefits of managed retreat

  • May help take pressure off existing defences
  • Creates new intertidal habitats
  • Defences can be installed further inland where more effective
• Costs of managed retreat

  • Relocation of people and demolition of buildings
  • Loss of land and property
  • Potential loss of cultural heritage
• River


  Carries excess water on land, mainly from precipitation, to the sea
• Channel


  The groove through which a river flows, consisting of its banks and bed
• Fluvial erosion


  1. Hydraulic action

  2. Abrasion

  3. Solution

  4. Attrition
• Hydraulic action is responsible for vertical erosion in the upper course of a river, making the valley deeper
• Hydraulic action contributes to lateral erosion of the banks in the lower course of a river, especially when fast-flowing water hits the outside bend of a meander
• Vertical erosion


  Deepening of the river bed, mostly by hydraulic action
• Lateral erosion


  Sideways erosion that wears away the banks of the river
• Fluvial transport


  1. Traction

  2. Saltation

  3. Suspension

  4. Solution
• Bedload


  Large boulders and rocks rolled along the river bed
• Suspended load


  Fine, light material (such as alluvium) held up and carried within the river's flow
• Solute load


  Minerals dissolved in the water
• Load mostly comes from material that has weathered and tumbled down the hillside, though some also comes from eroded river banks
• River velocity


  Determines what particle sizes are eroded, transported or deposited
• The Hjulstrom Curve shows the relationship between river velocity and particle diameter
• Velocity (cm/s)


  • 1000
  • 100
  • 10
  • 1
• Particle diameter (mm)


  • 0.01
  • 0.1
  • 1.0
  • 10
  • 100
• Fluvial processes


  • Particles eroded
  • Particles transported
  • Particles deposited
• Figure 11.4 The Hjulstrom Curve
• Give four types of fluvial erosion


  Write a sentence in your own words to describe each type
• Draw three annotated diagrams to describe how a rock fragment that has fallen into a river will change as it moves downstream


  Use appropriate adjectives, such as angular, jagged, rounded, rough and smooth
• In your annotations, explain the changes you have shown

  Include the following terms: attrition, transported, abrasion, traction, collide, banks and bed
• Load


  The material transported by a river
• Origins of load found in a river

  • Two origins
• Study Figure 11.4


  1. At what range of velocities will a 1.0 mm particle be transported?

  2. Below what velocity will a 1.0 mm particle be deposited?