Landslides and Geological Hazards

• Geological hazards are natural events causing major global problems.
• Urban expansion increases the impact and damage from these hazards.
• Most geological hazards are due to natural conditions, but some result from human actions.

Landslides

• They are ground movements on a sloping terrain, induced by gravity.
• Water from rain is a natural erosion agent, exacerbating landslides on slopes.
• Structures on steep mountains are highly vulnerable to landslides, especially during heavy rains.
• Key factors for rainfall-induced landslides are steep slopes, dense population, and denuded terrain.
• Long, regular rains can saturate the topsoil and bedrock, weakening soil bases.
• Plants and trees help by absorbing water and holding soil.

Types of Landslides

• Soil Creep Landslide: Very slow downslope movement of particles in loose, weathered material.
• Slumping Landslide: Downward movement of rock debris after removal of buttressing earth.
• Debris Flow Landslide: Triggered by slope saturation with water, causing water-soaked rock and soil to slide.
• Colluvial landslides in debris flow valleys can cause magnified secondary hazards if channel blockage occurs.
• Rock Fall Landslides: Sudden slides caused by heavy rain loosening rocks on slopes.

Sinkholes

• A topographic depression formed when groundwater dissolves underlying limestone bedrock.
• Sinkholes are often known as "sinks" or "dolines".
• They occur where soil has soft minerals/rocks like limestone, salt beds, or acidic rocks.
• Sinkhole depths range from meters to miles.
• Water seeps through cracks, eroding soil to form conduit systems that increase in size.
• The process can create voids filled with air or depressions that accumulate water.

Types of Sinkholes

• Cover Collapse Sinkhole: Develops suddenly, causing catastrophic damage, typically found where sediments contain clay.
• Cover Subsidence Sinkhole: Gradually grows where sediments are permeable and sandy.
• Dissolution Sinkhole: Occurs where calcareous rock is exposed or covered by thin soil and sand, mainly dissolving limestone or dolomite.
• Dissolution is most intense when water first contacts the rock surface.
• Artificial Sinkhole: Caused by human activities such as groundwater pumping or construction.
• Common causes of artificial sinkholes include mining, drilling, heavy construction, and increased water flow.

Causes of Geologic Hazards

• Climate: Long-term changes can significantly affect soil stability and water table levels.
• Earthquakes: Seismic activity contributes to landslides, especially on steep slopes.
• Weathering: Natural rock deterioration weakens materials, leading to landslides.
• Erosion: Sporadic running water removes slope support, causing landslides.
• Volcanic Eruption: In wet conditions, soil moves downhill, triggering landslides.
• Forest Fires: They burn vegetation, increasing runoff and erosion on slopes.
• Gravity: Steeper slopes combined with gravitational force can trigger landslides.
• Mining: Blasting weakens soils, increasing landslide risk.
• Clear Cutting: Eliminates tree roots, increasing water infiltration and landslide risk.
• Rainfall-Induced Landslides: Common in the Philippines due to frequent typhoons.

Causes of Sinkholes

• Dissolution of Sedimentary Rocks: Sinkholes form when sedimentary rocks dissolve, creating voids.
• Underground Water Pumping: alters water flow, eroding soil.
• Broken Pipes: Cause internal erosion, creating underground voids.

Warning Signs of Impending Landslides or Sinkholes

• Previous Landslides: Frequent occurrences indicate unstable geology.
• Tension Cracks: Show stress and friction from moving geological materials.
• Ground Movement: Identified by bending trees.
• Changes in rivers
• Water: Springs or groundwater may emerge unexpectedly.
• Trees or fence posts tilt or fall.
• New, small ponds appear after rain.
• Cracks appear in the ground.
• Sudden drainage occurs.
• Dips, depressions, and slopes form in the yard.

Geological Maps

• They show geological features, rock units, and strata using colors and symbols.
• Key features include faults, tilts, folds, and rock layers.
• Parts include Legend, Interpretation, Title, Susceptibility, and Sources.
• Symbols use thick/thin lines, capitalized letters for geologic units, and colors.
• Colors, patterns, and symbols are used to represent geology on maps.
• The letters signify rock unit age/name.
• Geologic maps condense information from fieldwork.
• Colors enhance usability.

Mitigation Strategies

• Protect schools, hospitals, and other important buildings.
• Adopt nonstructural mitigation measures to mitigate casualties from natural hazards and property damage.
• New developments resisted natural hazards.
• Preserve libraries and other cultural works.
• Identify valuable natural resources.
• Government facilities must be designed to resist natural hazards.
• Training programs are offered to improve implementation.
• Mitigations activities need improvement.
• Develop a family disaster plan and communication protocol.
• Have separate emergency supply kits for Home and Car.
• Duplicate essential documents.
• Keep a detailed inventory of possessions.

Precautionary Measures for Landslides

• Plant vegetation for soil compaction.

• Build diversion channels.

• Be aware of surroundings.

• Avoid runoff.

• Stay updated.

• Learn and participate in community plans.

• Be aware of the sounds.

• Stay away from debris.

• Stay alert and remain vigilant.

• Sinkholes Vary in Depth and shape.

• Find refuge. Stay away. Monitor damages. Don't throw anything inside. Secure property and go to a reliable location.

Hydrometeorological Hazards

• The Philippines vulnerability.
• Pacific Ring of Fire in the Philippines.
• Hydrometeorology definition.
• Weather forecasts and the weather parameters.
• Satellites and cloud images for tracking the weather.
• Numerical weather prediction.

Thunderstorms

• Short, disturbing, intense, and powerful weather.
• Storms in a 3 stage process.
• Cumulus stage: sun warms the air.
• Mature stage: raindrops begin to fall.
• Dissipating stage: down drafts dominate.

Flood and Flashfloods

• Rivers break from their banks.
• Inland flooding: occurs inland from miles from the coast.
• Flash floods: rain or release over over small periods of time.
• River and coastal flooding happen due to rising lake and river levels.
• Urban flooding drainage is lacking.

Storm Surges

• Daluyong ng bagyo; Irregular sea level rises.
• They occurs cyclone or "bagyo".
• PAGASA considers storms and weather factors.

El Nino and La Nina

• El Nino: Christ's Child, the little boy
• It is unusually warm water. Occurs from December.
• La Nina: Below average ocean water temps.
• ENSO.