Rainfall-Induced Geologic Hazards

• Geology: The study of the Earth's structure and composition, including the processes that have shaped the Earth's surface.
• Geology: anything that is related to the study of the earth's crust and its composition.
• Rainfall-Induced geologic Hazards: Hazards that are caused or triggered by rainfall, such as Landslide and sinkholes
• Landslides are also known as Landslip.
• Landslide: Ground movement in a sloping terrain which can be further induced by heavy rainfall.
• Guinsaugon Landslide

  • Occurred in Southern Leyte
  • During February 17, 2006
  • 1126 Deaths
  • Triggered by 10 days of heavy rain and small earthquakes
• DENR-MGB: Mines and Geosciences Bureau of the Department of Environment and Natural Resources
• Creep: slow and gradual movement of the soil, caused by rainfall
• Slump: Downslope flow of soft and unconsolidated materials
• Unconsolidated: Not compact soil
• Rock and Debris slides: slow to rapid downslope movement of unconsolidated soil and rock debris.
• Rockfall: Free falling movement of massive rocks from a cliff or steep slopes.
• Debris Flow: rapid flow of debris and other rock materials caused by rainflow
• Mudflow: similar to lahar; characterized by a flowing mass of mud along the flank of a volcano
• 3 characteristics of having a high risk to landslide: Steep slopes, Dense Population, and Denuded Ground
• Denuded Ground: the natural removal of natural materials in the ground
• Sinkholes: depressions or holes in the ground that result from the collapse of the surface layer of the soil. Similar to liquefaction. Occur in areas where the soil foundation is made of soft minerals and rocks such as silicate materials, salt beds, or any acidic rock.
• Bedrock Voids: Holes in the bedrock which are caused by ground movement
• Signs of impending Landslides and Sinkholes

  • Spring, water seepage, or water-saturated grounds that are not typically wet.
  • Soil that loosens and move away from foundations
  • New Cracks or unusual budges on cemented ground or walls
  • Underground utility lines that are broken due to vibrations or tremors.
  • Buildings, poles, walls and fences that are leaning.
  • Sudden rapid flow of creek waters carrying more silted water.
  • Signs of an imminent danger in groundwater.
  • Ponds that are certainly formed.
• Scientific Tools for Assessing Landslide

  • Abney Level or Clinometer: Used to define height of a certain area; functions like a telescope
  • Laser Rangefinder or Laser Telemeter: Used in Golf; Used to measure distance on how far an area is from a hazard
• Scientific Tools for Assessing Sinkholes

  • Ground Penetrating Radar (GPR): Detects different energies or motion of the ground
• Geohazard Map, Top 10 most landslide-prone provinces of the Philippines:

  1. Marinduque
  2. Rizal
  3. Cebu
  4. La Union
  5. Southern Leyte
  6. Benguet
  7. Nueva Viscaya
  8. Batangas
  9. Mountain Province
  10. Romblon
• If Your Area is Prone to Landslide

  • Plant more trees, grasses, and other vegetation.
  • Build channels for diversion of mudflow or debris flow
  • Do not build your house on or near a steep slope, mountain edges, drainages, or natural erosion valleys.
• BEFORE a Landslide

  • Be familiar with your surroundings.
  • Avoid open storm-water drainage and runoff.
  • Be updated on the news regarding the condition of your area.
  • Learn and participate in emergency responses and evacuation plans of your community.
• DURING a Landslide

  • Be attentive
  • Stay away from the path of debris.
  • Stay on elevated and sturdy area.
  • Curl into a tight ball and protect your head.
• AFTER a Landslide

  • Avoid the slide areas.
  • Listen for the latest emergency information.
  • Watch out for flooding.
  • Check for injured or trapped people near a slide
• If sinkholes are not detected earlier

  • Find refuge in a stable ground or open area.
  • Wait until the structures on and around the sinkhole stops moving.
  • Wait for the local government’s announcement
• AFTER a Sinkhole:

  • Stay away from the sinkhole
  • Monitor the damage on objects
  • Do not throw anything into the sinkhole
  • Secure whatever is left of your properties.