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mass movements - Coggle Diagram

- - - - high population density forces building on slopes
        
        high gradient - 30 percent of the total land area is 30 degrees steep or above
        
        natural terrain is naturally steep
        
        climate - wet season from may to September exacerbates risk
      - kowloon, hk island and new territories esp lantau
        
        over 2400 natural terrain landslides in lantau a year
    - - open hilliside la
      - channelised debris flow
      - deep seated failure
      - boulder fall
      - rock fall
- - - - particles of soil fall over time (decades)
  - - - triggered by intense rainfall, rapid snowmelt or volcanic activity
      - long profile with an extended lobe at the front
      - esp with weak rock or unconsolidated material
    - - -
        
        finegrained materials like clay, silt and fine sand
        
        thick viscous flow
        
        vary in speed
        
        tongues of material moving downhill
  - - - forms scree slopes
      - e.g. weathering, allows rock to be broken into smaller sections
  - - - when more permeable rock sits on top of clay, the clay layer eventually slumps
        
        forms terracettes
      - occurs due to a mix of impemeable and permeable rock esp due to waterlogging
    - - characteristic strata or layers of rock
- - - - triggered focus on mitigation
  - - - 200mm fresh water main severed