4. Natural Hazards, Mitigation and Adaptation.pdf

Understanding Natural Hazards and Their Impact  Introduction to Natural Hazards Natural hazards are Earth processes that can cause damage to property, injuries, or death. They can be classified as geological, hydrometeorological, or coastal. Understanding these hazards...

Understanding Natural Hazards and Their Impact  Introduction to Natural Hazards Natural hazards are Earth processes that can cause damage to property, injuries, or death. They can be classified as geological, hydrometeorological, or coastal. Understanding these hazards helps us prepare and mitigate their effects. Learning Objectives Describe why earthquakes, volcanic eruptions, and landslides are hazards and identify their effects. Identify areas prone to these hazards using maps. Suggest practical ways to cope with geological hazards. Identify human activities that trigger landslides. Describe why tropical cyclones, monsoons, floods, and waterspouts are hazards and identify their effects. Suggest ways to cope with hydrometeorological hazards. Explain coastal erosion, submersion, and saltwater intrusion. Propose ways to mitigate the impact of coastal processes.  Earthquakes: Causes and Effects Earthquakes occur due to the movement of tectonic plates. Effects include surface rupture, ground shaking, subsidence, liquefaction, and tsunamis. Can cause significant damage to buildings and infrastructure. Earthquakes are caused by the sudden release of energy in the Earth's crust. They can be classified into different types based on their causes and characteristics. Understanding these types helps in better preparation and response. Types of Earthquakes Based on the Cause: Tectonic Earthquakes Tectonic earthquakes occur due to the movement of tectonic plates. These are the most common type of earthquakes. Example: The 1990 Luzon earthquake in the Philippines, caused by the movement along the Digdig Fault. Effects included severe damage to buildings and infrastructure.  Types of Earthquakes Based on the Cause: Volcanic Earthquakes Volcanic earthquakes are triggered by volcanic activity. They occur when magma moves within the Earth's crust. Example: The 1991 Mount Pinatubo eruption in the Philippines, which caused numerous volcanic earthquakes. These earthquakes often precede or accompany volcanic eruptions.  Types of Earthquakes Based on the Cause: Collapse Earthquakes Collapse earthquakes occur in regions with significant underground voids. They are often caused by the collapse of caves or mines. Example: The 2012 earthquake in Negros Oriental, Philippines, which caused landslides and ground subsidence. These earthquakes are usually localized but can cause significant damage. Types of Earthquakes Based on the Cause: Human-Induced Earthquakes Human-induced earthquakes result from human activities like mining, reservoir-induced seismicity, and fracking. Example: The 2017 Leyte earthquake in the Philippines, possibly linked to geothermal energy extraction. These earthquakes highlight the impact of human activities on seismic activity.  Earthquake Outcomes Earthquakes can have various outcomes that impact the environment and human structures. Understanding these outcomes helps in preparing and mitigating their effects. Let's explore the different types of earthquake outcomes. Surface Rupture Surface rupture occurs when the ground breaks along a fault line. It can cause significant damage to buildings, roads, and infrastructure. Often visible as cracks or displacements on the Earth's surface. Example: The 1906 San Francisco earthquake.  Impact of Surface Rupture Surface rupture can sever utilities like water, gas, and electricity lines. Disrupts transportation networks, making rescue efforts difficult. Requires careful planning in construction to avoid fault lines. How can communities prepare for surface rupture?  Ground Shaking Ground shaking is the vibration of the ground caused by seismic waves. It can lead to the collapse of buildings and other structures. The intensity of shaking depends on the earthquake's magnitude and distance from the epicenter. Example: The 1994 Northridge earthquake in California. The 1994 Northridge Earthquake - YouTube Impact of Ground Shaking Ground shaking can lead to the collapse of poorly constructed buildings. Causes landslides in hilly or mountainous areas. Essential to follow building codes designed to withstand shaking. What measures can be taken to reduce damage from ground shaking?  Subsidence Subsidence is the sinking or settling of the ground surface. Can result from the compaction of soil or the collapse of underground voids. Often leads to damage in buildings, roads, and pipelines. Example: The 2011 Christchurch earthquake in New Zealand. Subsidence  Impact of Subsidence Subsidence can cause long-term damage to infrastructure. Affects drainage systems, leading to increased flood risk. Monitoring and early detection can help mitigate effects. How can we monitor and prevent subsidence in vulnerable areas?  Liquefaction Liquefaction occurs when saturated soil loses its strength during shaking. Causes the ground to behave like a liquid, leading to the sinking of structures. Common in areas with loose, water-saturated soils. Example: The 1964 Niigata earthquake in Japan.  Tsunami Tsunamis are large sea waves generated by underwater earthquakes. Can cause widespread flooding and destruction along coastlines. Often follow major subduction zone earthquakes. Example: The 2004 Indian Ocean tsunami.  Impact of Liquefaction Liquefaction can cause buildings to tilt or sink. Disrupts underground utilities and pipelines. Requires soil stabilization techniques in construction. What are some engineering solutions to prevent liquefaction damage?  Volcanic Eruptions: Causes and Effects Volcanic eruptions happen when magma reaches Earth's surface. Hazards include tephra, lahar, pyroclastic flow, and lava flow. Can lead to loss of life, property damage, and environmental changes.  Volcanic Products Volcanic eruptions produce various materials that can impact the environment and human life. Understanding these products helps us prepare and respond effectively. Let's explore the main products of volcanic eruptions.  Tephra: What Is It? Tephra includes all solid material ejected during a volcanic eruption. Ranges from fine ash to large volcanic bombs. Can travel long distances and affect air quality and climate. Example: The 1980 Mount St. Helens eruption.  Impact of Tephra Ashfall can damage crops, contaminate water supplies, and disrupt air travel. Heavy tephra can collapse roofs and damage infrastructure. How can communities prepare for tephra fallout?  Lahar: Volcanic Mudflows Lahar is a destructive volcanic mudflow composed of water and volcanic debris. Can travel rapidly down river valleys. Often triggered by heavy rainfall or melting snow and ice. Example: The 1985 Nevado del Ruiz eruption in Colombia.  Impact of Lahar Lahars can bury communities and infrastructure under thick layers of mud. Disrupt transportation and communication networks. What measures can be taken to mitigate lahar risks?  Pyroclastic Flow: A Deadly Hazard Pyroclastic flows are fast-moving currents of hot gas and volcanic matter. Can reach speeds of up to 700 km/h and temperatures of 1,000° C. Extremely destructive and deadly. Example: The 1902 eruption of Mount Pelée in Martinique.  Impact of Pyroclastic Flow Pyroclastic flows can obliterate everything in their path. Cause severe burns and respiratory issues for survivors. How can early warning systems help reduce the impact of pyroclastic flows? Lava Flow: Rivers of Fire Lava flows are streams of molten rock that pour from a volcanic vent. Can destroy everything in their path but move relatively slowly. Example: The 2018 Kilauea eruption in Hawaii.  Impact of Lava Flow Lava flows can destroy homes, roads, and agricultural land. Create new landforms and alter landscapes. What strategies can be used to divert or slow down lava flows?  Landslides: Causes and Effects Landslides involve the downward movement of rock, debris, or soil. Triggered by erosion, groundwater changes, volcanic activity, and earthquakes. Human activities like deforestation and mining can also cause landslides.  Identifying Hazard-Prone Areas Use hazard maps to identify areas prone to earthquakes, volcanic eruptions, and landslides. Helps in planning and preparing for potential hazards. Important for community safety and disaster management.  Coping with Earthquake Hazards Plan and practice earthquake drills with family. Prepare an emergency kit with food, water, and medicines. Secure furniture and objects at home to prevent injuries.  During and After an Earthquake Stay calm and follow the drop, cover, and hold drill. Exit buildings safely and avoid falling debris. Be aware of aftershocks and potential tsunamis.  Coping with Volcanic Eruption Hazards Plan for evacuation and prepare emergency supplies. Stay informed about volcanic activity and follow authorities' instructions. Use masks and protective clothing during ashfall.  Mitigating Landslide Hazards Avoid building structures near slopes and mountain edges. Plant trees to reduce soil erosion. Build retaining walls to support soil and prevent landslides.  Tropical Cyclones: Causes and Effects Tropical cyclones form over warm tropical oceans. Characterized by low pressure, high winds, and heavy rain. Can cause extreme winds, flooding, and storm surges.  Monsoons and Their Impact Monsoons are seasonal winds that bring significant weather changes. Amihan (northeast monsoon) is cool and dry. Habagat (southwest monsoon) brings heavy rainfall and humid weather.  Tornadoes and Waterspouts Tornadoes are violently rotating columns of air extending from thunderstorms. Waterspouts are similar but occur over water. Can cause severe damage with winds over 300 kph. Coping with Hydrometeorological Hazards Plan with family and prepare emergency kits. Stay informed about weather updates from PAGASA. Evacuate when instructed by authorities.  Coastal Erosion: Causes and Effects Coastal erosion is caused by waves, tides, and winds displacing sediments. Leads to instability and destruction of coastal structures. Can be gradual or abrupt due to storms.  Submersion and Saltwater Intrusion Submersion occurs when coastal areas are submerged by rising sea levels. Saltwater intrusion happens when seawater enters freshwater aquifers. Both can disrupt coastal communities and water supplies.  Mitigating Coastal Hazards Avoid building near oceans and seas. Use beach nourishment and shore protection structures. Plant mangroves and regulate groundwater use.  Discussion and Questions How can we better prepare for natural hazards in our community? What are some ways to reduce human impact on these hazards? How can technology help in predicting and mitigating natural hazards?  Conclusion Understanding natural hazards is crucial for safety and preparedness. Knowledge and planning can mitigate the impact of these hazards. Stay informed and proactive in protecting your community.