Landslides in Hong Kong

• Where is Hong Kong located?

  At the mouth of the Pearl River Delta
• What type of climate does Hong Kong have?

  Humid subtropical climate
• What are the characteristics of summers in Hong Kong?

  Hot and humid
• How are winters in Hong Kong described?

  Drier and mild
• What types of rocks are found in Hong Kong's geology?

  Granitic, volcanic, and sedimentary rocks
• Why are granitic rocks significant in Hong Kong?

  They are prone to deep weathering
• What geological features contribute to landslides in Hong Kong?

  Significant faulting, folding, and steep topography
• What role does vegetation play in Hong Kong?

  Stabilizes slopes
• What types of vegetation are found in Hong Kong?

  Woodlands, shrublands, and grasslands
• What is the slope gradient situation in Hong Kong?

  High gradients and steep topography
• Why are steep slopes in Hong Kong vulnerable to mass movements?

  They necessitate engineering and management for stability
• What was the impact of the June 1966 rainstorms in Hong Kong?

  Triggered massive landslides, killing 64 people
• How many people were made homeless due to the 1966 landslides?

  Over 2500 people
• How much rainfall was recorded during the June 1966 storms?

  Over 300mm
• What was unusual about the rainfall on June 11th and 12th, 1966?

  Over 400mm fell, with ⅓ in one hour
• How much total rainfall was recorded by June 15, 1966?

  Over 1650mm
• How many landslides were recorded in June 1966?

  700 landslides
• How did vegetation affect landslides in Hong Kong?

  Trees held back smaller landslides
• What happens when deforestation occurs in Hong Kong?

  Reduces soil stability, increasing erosion risk
• How does urbanization affect slope stability in Hong Kong?

  Vegetation is cleared, increasing landslide risk
• What is the impact of construction on previously vegetated slopes?

  Adds weight and stress, destabilizing them
• How does hydrology change affect landslides in Hong Kong?

  Less interception increases soil saturation
• What is the area of Hong Kong?

  1075 km²
• What is the population of Hong Kong?

  7 million people
• What is the terrain like in Hong Kong?

  Natural steep terrain and hills
• What is the slope gradient of upper slopes in Hong Kong?

  Steeper than 30 degrees
• Where is most of the population concentrated in Hong Kong?

  Along less steep urban areas
• What triggers landslides during construction in Hong Kong?

  Excavation and building works
• What are the techniques used to reduce mass movement in Hong Kong?

  • Slope safety system
  • Surface drains
  • Mulching system
  • Long rooting grass
  • Fibre reinforced soil system
• What is the purpose of the slope safety system in Hong Kong?

  To maintain slope safety through investigation
• What is the government intervention regarding slope safety?

  Owners must take responsibility for slope safety
• What happens if a private slope does not comply with regulations?

  Prosecution leads to a HK$50,000 fine
• How much has the risk of landslides reduced since 1977?

  By 50%
• What is the function of surface drains in Hong Kong?

  Divert water from unstable sites
• What is an advantage of surface drains?

  Least expensive and effective way
• What is a disadvantage of surface drains?

  Vulnerable to blockage without maintenance
• What is the purpose of a mulching system?

  Provides protective cover for vegetation growth
• What are the advantages of a mulching system?

  High resistance to rain erosion
• What is a disadvantage of a mulching system?

  Increases surface runoff when not managed
• What is the purpose of long rooting grass in slope management?

  Secures soil in place