dams

• Dams:

  • Water storage 
  • Flood prevention 
  • Hydroelectric
• Planning:

  • Volcanic activity 
  • Seismic activity 
  • Faults 
  • Metallic mineral veins in catchment area 
  • Mass movement - landslides and unlithified deposits 
• Anticlines are unstable, tension joints allow percolation of water. Limb slippage may occur downstream. 
• Synclines are stable, but water may pass under dam in permeable beds. 
• Downstream dips are unstable, weight of the dam pushes down on bel=dding planes and water may leak. 
• Upstream dips are stable. 
• Horizontal beds are stable. 
• Dams should be build on one rock type. 
• Best place for dams are u shaped valleys and v shaped valleys. Narrow points mean less width of dam needed. 

  • Ideally a syncline. 
• Concrete dams are arch shaped. Curved upstream to add strength, suitable for narrow gorges. Underlying rock must be competent with a high UCS. 

  • Hoover 
• Concrete dams can also be gravity dams. Held in place due to gravity due to mass of concrete. If found on impermeable, high UCS rocks it is very strong.

  • Can be hollow 
  • Three gorges 
• Embankment dams are made of impermeable clay or concrete. 

  • Built in wide valleys because its less expensive 
  • Less strong from lack of concrete 
• Grouting:

  • Holes drilled into rock 
  • Pump liquid cement 
  • Cement solidifies in pore spaces 
  • Reduces porosity and permeability 
• Cut off curtains:

  • Concrete extension below dam 
  • Prevents leakage 
  • Prevents slippage of beds 
• Geomembrane:

  • Reservoir lining with impermeable substances 
  • Clay or plastic 
  • Prevents leakage 
• Consequences:

  • Appearance 
  • Destruction of habitats 
  • Land take 
  • Flooding upstream 
  • Noise pollution 
  • Migration barriers