L3: Hydrometeorological Hazards

• FLOOD

  ● The overflowing of the normal confines of a steam or bodies of water, or the accumulation of water over areas that are not normally submerged.
• TYPES OF FLOOD

  • River Floods
  • Flash Floods
  • Coastal Floods (Storm Surge)
• River Floods

  ● Occurs when the water level in a river, lake or stream rises and overflows onto the surrounding banks, shores and neighboring land.
• Flash Floods

  ● Characterized by an intense, high velocity torrent of water triggered by torrential rain falling within a short amount of time within the vicinity or on nearby elevated terrain.
• Coastal Floods (Storm Surge)

  ● Happens when the sea level rises that results in flooding on the surrounding low-lying areas.
• Color-Coded Rainfall Advisories

  • Red Warning
  • Orange Warning
  • Yellow Warning
• Red Warning

  • More than 30 mm rain observed in 1 hour and expected to continue in the next 2 hours
  • Torrential
  • Serious flooding expected in low-lying areas
  • Evacuation
• Orange Warning

  • 15-30 mm rain observed in 1 hour and expected to continue in the next 2 hours
  • Intense
  • Flood is threatening
  • Alert for possible evacuation
• Yellow Warning

  • 7.5-15 mm rain observed in 1 hour and expected to continue in the next 2 hours
  • Heavy
  • Flooding is possible
  • Monitor the weather condition
• THUNDERSTORM

  ● Generally local storms produced by cumulonimbus clouds.

  ● Always accompanied by lightning and thunder, usually with strong wind gusts, heavy rain and sometimes with hail and/or tornado.
• SIGNS OF AN IMPENDING THUNDERSTORM

  1. Accumulation of cumulonimbus clouds
  2. Darkening of the skies
  3. Presence of lightning and strong wind
  4. Sounds of thunder
  5. Production of static on communication equipment
• Before a Thunderstorm

  1. In preparing just in case a lightning strikes, make sure to limit electric contact around the vicinity of the house.

  ➔ Remove dead tree branches

  ◆ These may cause a fire once struck by lightning

  ➔ Unplug all appliances before the storm hits

  ◆ This is to prevent power surges

  ➔ Close all blinds and shades
• During a Thunderstorm

  ➔ Stay away from windows

  ➔ Avoid Phone use

  ➔ Stay away from water

  ➔ Keep windows shut

  ➔ Find a place outside that is unlikely to flood if no shelter is available

  ➔ Squat low to the ground and assume a tucked position

  ➔ Dropping into the tucked position if a hair feels like it’s standing on end
• After a Thunderstorm

  [1] Help a person who has been struck by lightning

  ➔ Don’t be afraid to touch the person as it would not carry a charge after it has been struck by lightning.

  [2] Administer first aid or CPR immediately

  ➔ A lightning victim usually suffers burns in two places on the body – where the lightning entered and where it exited.
• STORM SURGE

  ● The sudden rise of sea level caused by strong winds and low atmospheric pressure from an approaching tropical cyclone.

  ● Storm surges can inundate coastal areas, leading to extensive flooding, property damage and loss of life.

  ○ The Philippines has many coastal communities making it particularly vulnerable to storm surges during typhoons.
• EL NIÑO AND LA NIÑA

  ● Collectively known as the two alternating phases of the El Niño-Southern Oscillation, or ENSO for short.

  ○ El Niño = The Little Boy = Dry Phase

  ○ La Niña = The Little Girl = Cold Phase
• El Niño pulls away the rain from the Philippines, leaving dry, hot, drought-prone conditions. It occurs:

  [1] When trade winds weaken or reverses;

  [2] The warm water near the Philippines (west pacific) moves eastward.

  [3] The lack of warm water bring about various consequences:

  ■ Less moisture

  ■ Less rainfall

  ■ High Risk of Drought

  ■ Fewer Typhoons

  ■ Dry season becomes longer and hotter
• La Niña adds extra rain to the Philippines, causing wet, stormy, and flood-prone conditions. It occurs by:

  [1] When trade winds become stronger than normal;

  [2] The warm water near the Philippines (west pacific) piles up and increases.

  [3] The lack of warm water bring about various consequences:

  ■ Warm water gets even more warmer, causing stronger cloud formation.

  ■ Above-normal rainfall

  ■ High Risk of Flooding and Landslide;

  ■ Stronger and more frequent typhoons.

  ■ Rainy season may start earlier and/or last longer
• Trade Winds play an important role in ENSO by controlling where warm water goes. During the cooldown time when ENSO is inactive, the trade winds normally go from the East to West and towards the Equator.
• Warm Water plays an important role in the effects of weather since warm water’s main role is to evaporate and form clouds.

  ○ Due to trade winds normally pushing warm water towards the east, the

  Philippines become prone to typhoons because of the warm water build-up.