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Questions and Answers
What typically causes coastal flooding?
What typically causes coastal flooding?
Which flood type is characterized by a rapid rise of water in a short amount of time?
Which flood type is characterized by a rapid rise of water in a short amount of time?
What alert indicates that flash flooding has been reported or is imminent?
What alert indicates that flash flooding has been reported or is imminent?
What is primarily affected when urban areas experience flooding?
What is primarily affected when urban areas experience flooding?
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Which situation is most likely to cause inland flooding?
Which situation is most likely to cause inland flooding?
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What is the most dangerous characteristic of flash floods?
What is the most dangerous characteristic of flash floods?
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What typically leads to river floods during tropical storms?
What typically leads to river floods during tropical storms?
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Which method is effective for flood damage mitigation?
Which method is effective for flood damage mitigation?
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What is the recommended action after experiencing a typhoon regarding personal safety?
What is the recommended action after experiencing a typhoon regarding personal safety?
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What should one be cautious of when flood waters are present?
What should one be cautious of when flood waters are present?
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When assessing high water marks after a flood, which is most important?
When assessing high water marks after a flood, which is most important?
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Which of the following is a critical aspect of storm surge mitigation?
Which of the following is a critical aspect of storm surge mitigation?
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What type of flood generally occurs after prolonged heavy rainfall?
What type of flood generally occurs after prolonged heavy rainfall?
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Which system is essential for providing flash flood alerts in response to sudden rain?
Which system is essential for providing flash flood alerts in response to sudden rain?
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What visual cue may indicate an approaching tsunami?
What visual cue may indicate an approaching tsunami?
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During storm preparations, which action should be prioritized to help ensure safety?
During storm preparations, which action should be prioritized to help ensure safety?
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What is the primary advantage of using tide stations for measuring storm surge?
What is the primary advantage of using tide stations for measuring storm surge?
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What is a significant disadvantage of high water marks in measuring storm surge?
What is a significant disadvantage of high water marks in measuring storm surge?
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What unique information can pressure sensors provide in storm surge mitigation?
What unique information can pressure sensors provide in storm surge mitigation?
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Which factor does NOT contribute to flooding as defined in the content?
Which factor does NOT contribute to flooding as defined in the content?
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What is a limitation commonly associated with pressure sensors used for storm surge monitoring?
What is a limitation commonly associated with pressure sensors used for storm surge monitoring?
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Which statement describes a disadvantage of using high water marks for storm surge assessment?
Which statement describes a disadvantage of using high water marks for storm surge assessment?
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What is one of the major benefits of deploying tide stations along the coast?
What is one of the major benefits of deploying tide stations along the coast?
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What characteristic is critical in flood events that does NOT depend on storm surges?
What characteristic is critical in flood events that does NOT depend on storm surges?
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Study Notes
Hydrometeorological and Coastal Processes and Hazards
- Hydrometeorological phenomena cause hazards and may accelerate coastal processes.
- Hazards can be mitigated through government and private initiatives.
- The Philippines has 7,641 islands and a coastline of approximately 36,289 km.
Coastal Processes and Hazards
- Coastal processes include erosion, submersion, and salt intrusion.
- Coastal landforms are affected by these processes.
Typhoon
- Tropical cyclones in the northwestern Pacific Ocean are called typhoons in the Philippines.
- A Filipino word, "bagyo," is used to refer to a typhoon.
- The term "bagyo" originated from a 1911 typhoon that brought 46 inches of rainfall in 24 hours to Baguio City.
Hurricane, Typhoon, and Tropical Cyclone
- The terms "hurricane" and "typhoon" are regionally-specific names for a strong tropical cyclone.
- Tropical cyclone is the generic term for a non-frontal synoptic-scale low-pressure system over tropical or subtropical waters with organized convection and a definite cyclonic surface wind circulation.
- Winds of 33 m/s (64 km/h, 74 mph) or higher are classified as hurricanes (North Atlantic Ocean, Northeast Pacific Ocean east of the dateline, or South Pacific Ocean east of 160E) or typhoons (Northwest Pacific Ocean west of the dateline), severe tropical cyclone (Southwest Pacific Ocean), or very severe cyclonic storm (North Indian Ocean), or tropical cyclone(Southwest Indian Ocean).
Categories of Typhoon
- Category 1 (Tropical Depression): Winds between 119 and 153 km/h. The initial stage of a typhoon's formation.
- Category 2 (Tropical Storm): Winds between 154 and 177 km/h. A system of intense thunderstorms that intensify.
- Category 3 (Strong Typhoon): Winds between 178 and 209 km/h. A system of low pressure, and intense winds.
- Category 4 (Intense Typhoon): Winds between 210 and 249 km/h. Classified as a Category 5 storm and carries the highest element of risk.
- Category 5 (Violent Typhoon): Winds exceeding 249 km/h. Characterized by extreme winds.
Typhoon Death Toll (Philippines)
- Data displays typhoon death tolls for various typhoons between 2004 and 2014.
List of Philippine Historical Typhoons (1970-2011)
- Provides data on historical typhoons including names, periods of occurrence, deaths, damage amounts, highest wind speeds, and areas affected.
2024 Typhoon Names
- A list of typhoon names planned for the 2024 season is included.
Monsoons
- The Philippines experience both Northeast (Amihan) and Southwest (Habagat) monsoons.
- Northeast monsoon (Amihan) is characterized by moderate temperatures and little to no rain in central and western Luzon and Visayas, with a prevailing east wind.
- Southwest monsoon (Habagat) occurs from June to July and ends in September or October. It's associated with western or southwest winds, humid weather, frequent heavy rainfall, and prevailing wind from the west.
Stages of Typhoon
- Formative Stage: The initial stage where the tropical cyclone forms in waves and pre-existing disturbances, with winds remaining below typhoon force.
- Immature Stage: The deepening stage of the cyclone.
- Mature Stage: The stage of maturity when the areas of circulation expand and surface pressure no longer decreases, with maximum wind speed lasting for a week.
- Decaying Stage: The dissipating stage where the surface pressure rises and the area affected by the cyclone diminishes in size.
Structure of Typhoon
- The eye is the relatively calm center of a typhoon, characterized by clear skies, sinking air, and light winds, usually with speeds below 15 mph (24 km/h).
- The eyewall is a ring of thunderstorms that produce heavy rains and the strongest winds surrounding the eye.
- Rainbands are curved bands of clouds and thunderstorms that trail away from the eyewall in a spiral fashion.
Effects of Typhoons
- Strong wind
- Tornadoes
- Rainfall
- Floods
- Possible storm surge
Typhoon Mitigation
- General actions before include increasing risk knowledge, determining community hazards, and planning accordingly. General actions during a watch and warning include preparing evacuation plans, gathering supplies, and securing property.
- General actions after include checking with authorities and potentially helping those injured from the storm. The specifics of these actions are detailed in the mitigation sections of the notes.
Destructive Waves
- Tsunami
- Tidal waves
- Storm surge
Tsunami
- A series of waves caused by sudden, large undersea earthquakes at tectonic plate boundaries.
- The waves can travel very fast, across the open ocean at approximately 700-800 km/h (435-500 mph).
- Most tsunamis occur within the Pacific Ocean's “Ring of Fire.”
- Earthquakes shift tectonic plates.
- A large amount of water vertically is displaced.
Tsunami Formation
- An earthquake caused by sliding of one tectonic plate under another causes the sea bed to rise, displacing a vast amount of water vertically.
- The dome of water returns to its natural level, resulting in a wave.
- As the wave approaches shallower water, friction causes it to slow down but build up in height.
Signs of Tsunami
- Severe ground shaking from local earthquakes
- Water may recede from the coast, exposing the ocean floor.
- Abnormal ocean activity
- Loud "roaring" sound similar to a train or jet.
Warning Signs of Tsunami
- Earthquakes are a natural warning.
- Watch for a noticeable fall or rise in water level
- Unusual rapid or far receding water
- Information provided by radio and television
Tidal Wave
- A shallow water wave caused by gravitational interactions between the Sun, Moon, and Earth on the ocean.
- The Sun and moon's gravitational pulls are evident in tides.
Storm Surge
- Abnormal rise in seawater level during a storm, measured as the height of the water above the normal predicted astronomical tide.
- Storm's winds push water onshore.
Causes of Storm Surge
- Wind circulation around the typhoon's eye
- Vertical circulation in the ocean becomes disrupted when shallow waters extend near the coast
- Winds blowing onshore during the storm
Water Composition of Total Water Level
- Tides
- Waves
- Freshwater
Storm Surge Mitigation
- Tide Stations measure variation in water level along coast. These can calculate storm surge by subtracting base water levels.
- High Water Marks are lines on trees or structures where the water reached during a flood. These are a traditional method for measuring surge height but have significant limitations in real-time availability, persistence, and subjectivity.
Flood
- An overflowing of water onto normally dry land.
- Can happen during heavy rains, when ocean waves come ashore, when snow melts quickly, or after dams or levees break.
Flash Flood
- The most dangerous kind of flood, due to extreme speed and unpredictability.
- Occurs when excessive water quickly fills normally dry creeks, riverbeds, and rapidly rising river channels, often with little warning.
Alert in Identifying Flood
- Flood Watch: Possible flash flooding or flooding.
- Flash Flood/Flood Warning: Flash flooding or flooding has been reported.
- Urban and Small Stream Advisory: Flooding of small streams and low-lying areas, and related infrastructure, is occurring.
- Flash Flood/Flood Statement: Follow-up information regarding a flash flood event.
Types of Flood
- River Flood: Water levels rise above the riverbanks due to excess rain from tropical systems or persistent thunderstorms.
- Coastal Flood: Undirectional floodwater inundates land along the coast, worsened by higher-than-average tides and heavy rains.
- Inland Flooding: Moderate to intense precipitation over a sustained period causes river overflows or flooding due to debris or ice jams.
- Flash Flood: Resulting from heavy to excessive rainfall within a short period of time, these result in rapid and severe rises in water levels in creeks, riverbeds, urban streets, and mountain canyons.
Flood Mitigation
- Knowing the risk by having information on risk.
- Creating an emergency communications plan.
- Building an emergency kit.
- Considering flood insurance policy protection of your family and belongings.
- Elevating furnace, water heaters, and electric panels to prevent flooding.
- Constructing barriers (e.g. sandbagging) into the home and surrounding areas; sealing walls in basements with waterproofing materials.
Tornado
- Vertical funnels of rapidly spinning air.
- Can have winds as high as 250 miles per hour, clearing a mile-wide path.
Tornado Facts
- Tornadoes form due to changes in wind speed and direction within a storm cell.
- Meteorological factors that increase chances of tornadoes, are more prevalent in late afternoon, spring, and summer.
- Tornadoes' distinctive funnel clouds are transparent; they become visible due to moisture condensing or dust/debris being picked up.
Cause of Tornado
- Supercells (large thunderstorms with pre-existing rotation).
- Updrafts of wind that rotate around a vertical axis.
Classification of Tornado
- Multivortex (multiple-vortex): Contains multiple, small, intense subvortices orbiting a larger, central vortex.
- Waterspout: A tornado over water, often smaller and weaker than Great Plains tornadoes but still dangerous to boats and people on land.
- Landspout: A non-supercell tornado, resembling a waterspout in appearance, but can be a significant localized hazard.
- Gustnado: Small, weak whirlwind resulting from an eddy in thunderstorm outflows.
- Dust Devil: Small, rapidly rotating wind that picks up dust, dirt, or debris.
Tornado Mitigation
- If you are under a warning: Find safe shelter immediately (sturdy building, safe room, lowest level, away from windows, doors and outside walls). Do not get under an overpass or bridge.
- Prepare Now: Know the signs of an approaching tornado, listen to weather reports, and identify a safe shelter.
- Survive During: Immediately seek a safe location identified beforehand, shield head and neck and put barriers like furniture or blankets around you. Do not try to outrun a tornado in a vehicle.
El Niño and La Niña
- El Niño and La Niña are opposite phases of the El Niño-Southern Oscillation (ENSO) cycle. ENSO describes temperature fluctuations between the ocean and atmosphere in the east-central Equatorial Pacific Ocean (approximately between the International Date Line and 120 degrees West).
- La Niña: Cold phase of ENSO.
- El Niño: Warm phase of ENSO.
Effects of La Niña
- Increased rainfall
- Catastrophic floods
- Drier conditions than usual
- Increased commercial fishing
- Affects climate patterns
- Affects weather cycles
Effects of El Niño
- Effects on global weather patterns
- Variations in temperature and precipitation
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