Landslides and Sinkholes

• Geological hazards are natural phenomena causing major worldwide problems
• Increased urbanization raises impact/damage from geological hazards
• Hazards relate to natural conditions but can stem from humans

Landslides & Sinkholes

• Landslides are called mudslides, flash floods, avalanches, etc., differing in composition but require inclined terrain
• Sinkholes are on elevated or flat surfaces, ranging from massive to small
• Knowledge of landslide and sinkhole types is essential for preparedness

Landslides Defined

• A landslide is ground movement on a slope
• Water is a natural erosion agent worsening landslides
• Steep-slope mountain structures are highly vulnerable, especially with heavy rainfall
• Steep slopes, dense population, and denuded terrain increase rainfall-induced landslide risks
• Plant roots are important to absorb water and hold soil
• A downpour can quickly trigger landslides, mudslides, or mudflows

Types of Landslides

• Soil Creep Landslide: Very slow downslope movement of particles
• Slumping Landslide: Downward movement of rock debris after buttressing earth removal
• Debris Flow Landslide: Slope saturated with water triggers a slide of water-soaked rock and soil
• Rapid rainfall can quickly cause colluvial landslides in debris flow valleys
• Rock Fall Landslides: Sudden slides caused by undermined rock due to heavy rain

Sinkholes Defined

• Sinkholes are topographic depressions from groundwater dissolving limestone bedrock
• Common names are "sink" or "doline"
• The soil foundation in sinkhole areas is soft minerals, rocks, limestone, salt beds, or acidic rocks

Sinkhole Formation

• Rainfall seeps through cracks, eroding soil, and creating underground water systems
• Systems can form voids filled with air, and with underground drainage
• Clogged voids form depressions that accumulate water and ponds
• Collapse into a void forms a hole, filled with air or water

Types of Sinkholes

• Cover Collapse Sinkhole develops suddenly (over hours), causing catastrophic damage
• Cover Subsidence Sinkhole gradually grows where sediments are permeable and sandy
• Dissolution Sinkhole occurs where calcareous rock is exposed, dissolving limestone fastest where water first contacts it

Artificial Sinkholes

• Artificial Sinkholes are caused by human activity such as groundwater pumping and construction
• Common causes include mining, drilling, weight changes, and increased water flow from artificial ponds

Causes of Geologic Hazards: Landslides

• Climate: Impacts soil stability through precipitation changes
• Earthquakes: Soil shifts during tectonic plate movement, and ash debris flows cause mass soil movement
• Weathering: Rock deterioration leads to weak, landslide-susceptible materials
• Erosion: Running water, wind, and waves remove slope support
• Volcanic Eruption: Soil moves downhill, especially from stratovolcanoes with wet conditions
• Forest Fires: Burns vegetation, increases runoff and erosion
• Burrowing insects: They aerate the soil during a wildfire and makes it unstable
• Gravity: Steeper slopes increase gravitational force

Human Causes of Landslides

• Mining: Blasting weakens soil and earthwork alters slopes
• Clear-cutting: Timber harvesting decimates root structure and changes water infiltration
• Rainfall-Induced Landslides: The most common and widespread landslides with an average of 20 typhoons each year in the Philippines depend on soil conditions.
• The accumulated rainfall, length and severity, and terrain slope have the greatest effect on the stability of the slope.
• Rainfall-induced landslides still rely on the type of land covered and the type of soil

Natural Causes of Sinkholes

• Sinkholes occur when sedimentary rocks are dissolved, voids of water or air are formed

Human Causes of Sinkholes

• Pumping water and altering drainage systems can cause a change that results in internal erosion
• Broken pipes underground cause internal erosion for voids

Signs of Impending Landslides

• Earlier landslides in the same area is an indicator, implying weak soil and unstable geology
• Multiple landslide events indicate retrogressive, piecemeal, or reactivated landslides
• Tension cracks indicate stress and friction, cracks are located on higher elevation
• Movement of trees, tilting and creaking can indicate a landslide
• Water doing something different, seeps or springs in dry terrain

Impending Sinkhole Signs

• Trees or fence posts that tilt or fall
• Foundations slant
• Appearance of new ponds after rain
• Cracks in the ground
• Changes in water drainage
• Dips, depressions, slopes in yards
• Dead patches of grass or plants
• Issues in nearby sinkholes and vegetation in a limited area
• Discolored or contaminated well water
• Cracking or buckling of concrete, unusual bugs like slugs or centipedes show up

Geological Maps Defined

• These maps show geological features, rock units, and strata using colors/symbols

Features of Geological Maps

• Faults
• Tilts
• Folds
• Rock layers

Geological Map Elements

• Legend
• Interpretation
• Title
• Susceptibility
• Sources

Symbols in Geological Maps

• Thick and thin lines
• Capitalized letters for the geologic unit
• Colors

Mitigation Strategies

• Vulnerability and exposure to geohazards are determined and validated through scientific tools, visible signs, and maps.

Intensity Nation's Hazard Mitigation Via:

• Locating new schools/hospitals outside hazardous areas and reinforcing existing ones
• Using nonstructural measures to mitigate harm, for example, securing furniture
• Incorporating mitigation into new developments (hazard assessment data, land use plans, and zoning regulations)
• Protecting cultural/natural resources such as species of wildlife, fish, and plants
• Following regulations that fund/regulate/lease buildings must follow modern building codes
• Implementing mitigation training
• Performing Hazard-specific research to improve mitigation practices

Action Plans to Protect Human Lives and Properties

• Develop and rehearse family disaster plans for potential evacuation
• Create communications plans to contact each other if separated
• Assemble emergency kits with food, water, first aid, flashlights, radios, batteries, flares, and jumper cables for vehicles
• Make sure the family knows how to shut off appliances/resources
• Duplicate important documents
• Detailed inventory of personal belongings/property with photos/videos stored safely

Precautionary Actions for Landslides

• Plant more trees to enhance soil compaction and erosion prevention
• Build mudflow or debris flow diversion channels

Actions Before a Landslide

• Knowing surroundings, watching changes to objects, and preparing
• Avoid open storm-water drainage because debris and soil may be collected
• Stay Informed
• Having emergency plans in place

Actions During a Landslide

• Watch for unusual occurences and listen for unusual sounds, such as boulders knocking together
• Stay away from the path of debris
• Stay alert and awake
• Locate sturdy and elevated areas, otherwise curl into a ball and protect the head

Actions After a Landslide

• Stay away until it is safe from the authorities
• Check for hazards/injuries and report immediately

Sinkholes

• The sinkhole is a depression or hole in the ground caused by some form of surface layer collapse
• Chemical dissolution of carbonate rocks or suffosion occur to create sinkholes

Sinkhole Actions

• In an event that sinkholes are not detected earlier and it appears suddenly, do the following:
• Find refuge in a stable ground or open area.
• Do not attempt to go back and retrieve your belongings.
• Wait for local government's announcement when it is safe to go back.
• Check the damages on objects. For example, if the crack gets longer or wider the sinkhole may still enlarge.
• Do not throw anything into the sinkhole.
• Secure whatever is left of your properties and relocate to safe grounds.

Hydrometeorological Hazards Defined

• The Philippines is very vulnerable to natural hazards and disasters like typhoons, earthquakes, floods, volcanic eruptions, landslides, and fires

Types of Hydrometeorological Hazards

• Typhoon
• Thunderstorm
• Flood
• Flashflood
• Storm Surge
• El Niño
• La Niña

Signs of Impending Hydrometeorological Hazards

• Tropical cyclone or a typhoon: An intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain Weather Forecast is a scientific estimate of future weather condition

Steps of Weather Forecasting:

• Observation
• Collection and Transmission of Weather Data
• Plotting of Weather Data
• Analysis of Weather Maps, Satellite and Radar Imageries and Other Data
• Formulation of the Forecast

Thunderstorms Defined

• Thunderstorms occur when layers of dry, moist air rise to cooler regions of the atmosphere in a broad, rapid updraft.
• Cumulus Stage where the sun heats the Earth's surface during the day and warms the air around it.
• Mature Stage cumulus cloud becomes very large as water becomes large and heavy
• Dissipating Stage, the thunderstorm begins to dissipate when the downdrafts in the cloud begins to dominate over the updraft.

Floods Defined

• Flood is a high-water stage in which water overflows its natural or artificial banks onto normally dry land, such as a river inundating its floodplain

Storm Surge Defined

• Storm surge or "Daluyong ng Bagyo" in the Philippine system occurs when the irregular sea-level rise occurs during a tropical cyclone or bagyo

El Niño Defined

• Niño was originally recognized by fishermen off the coast of South America in the 1600s, with the appearance of unusually warm Pacific Ocean water

La Niña Defined

• La Niña episodes represent periods of below-average sea surface temperatures across the east-central Equatorial Pacific. And global climate La Niña impacts tend to be opposite those of El Niño impacts