ENVIRONMENTAL GEOLOGY TKG 433

ENVIRONMENTAL GEOLOGYTKG 433GEOHAZARDS (BENCANA GEOLOGI)

Hazard as a Natural ProcessGeological process:Endogene & ExogeneMenyebabkan kerusakan dan kehilangan harta benda & nyawa, sebab:Manusia tinggal di dekat kawasan rawan bencanaPerubahan fungsi lahan flooding / landslideFrequency (recurrence interval) vs magnitude (amount of energy released); inversely relatedLarge floodVolcanic eruptionEarthquakeless frequentMagnitude-Frequency Concept

small magnitude, high frequencyhigh magnitude, less frequencymoderate magnitude, moderate frequency

Inverse relationship between magnitude and frequencyMuch of the work forming the earth surface is done by events of moderate magnitude and frequencyBenefits of Natural HazardsRiver floodingNutrient to floodplainsDelivering sediment to beachesFlushing pollutants

LandslidesForming dam produce lakes

Volcanic eruptions Create new land (Hawaii)Nutrient-rich volcanic ash

EarthquakesFault gouge: groundwater barrier (subsurface dam)Mountain building

Death and Damage by Natural Hazards

H = high; M = medium; L = lowTypes of GeohazardGeobencana aktif(Bencana alamiah)Geobencana pasif(Ada campur tangan manusia)Earthquake

Landslide/slope failureVolcanoSubsidenceHurricaneFloodingTornadoesErosionTypes of Geohazard

Types of GeohazardSlope failure / rapid subsidenceTsunamiCycloneFlash flood (rapid flood)VolcanoEarthquakeSlope erosionLandslideFloodErosionSlow subsidenceSoil creepminormajorSizefastSpeedslowHazardous Events(Aswathanarayana, 1995)

Natures Top Ten Most Destructive Forces10. WATER (Waterfall)9. GEYSER8. LIGHTING & THUNDER7. WILD FIRE6. RAIN AND FLOODING5. AVALANCHE4. OCEAN (giant waves) TSUNAMIS3. SUPER WIND2. EARTHQUAKE1. SUPERVOLCANO10-6 : Can be avoided and escaped1-5 : Faster and very difficult to escapeAtlantic Tropical Storms Names

Disaster Prediction & WarningLocationProbability of occurrencePrecursor eventsForecastingWarning

Disaster Prediction & Warning

Disaster Prediction & Warning

Risk AssessmentRisk of particular event = (probability of that event occur) x (consequence of the event)

Consequence = damage to people, property, economic activity, public service, etc)Ex: Large earthquake; low probability but high consequence

Acceptable risk Minimum risk that people can accept

Human response to hazardsLand-use planningAvoid build on floodplains or active landslidesInsurance Flood insurance Earthquake insuranceEvacuationNeed sufficient time to evacuateDisaster preparednessTraining Artificial control of natural processesRetaining wall against landslideFlood control dams; levees; smart tunnel;

Human Response to Hazards

Human Response to Hazards

Pertambahan Penduduk dan Peristiwa GeobencanaPertambahan penduduk menyebabkan manusia terpaksa tinggal berdekatan dengan kawasan bencanaCth1: Mexico City 23 million in 2300km2City is built on ancient lake bedsSeptember 1985; 7.8 magnitude; 10,000 killedCth2: Colombian volcano del Ruiz1845 mudflow; killing 10001985 another mudflow; 21000 killed

Thank You

Courtesy of: Assoc. Prof. Dr. Wan Zuhairi Wan YaacobGeology DepartmentThe National University of Malaysia