Lesson 2: Hydrometeorological Hazards and Disasters

Question 1

Hydrometeorological hazard

Answer 1

• “Process or natural phenomenon of atmospheric,
  hydrological or oceanographic nature that may
  cause loss of life, injury or other health impacts,
  property damage, loss of livelihoods and
  services, social and economic disruption, or
  environmental damage” (UNISDR, 2007)

Question 2

Various hydrometeorological hazards that we often
experience in the Philippines

Question 3

A. El Niño

Answer 3

The warm and cool phases of a recurring climate
pattern across the tropical Pacific—the El
Niño-Southern Oscillation, or “ENSO” for short.
Because ENSO involves interaction between the
ocean and the atmosphere – both of which play a
role in reinforcing changes in each other – it is
known as a coupled ocean-atmosphere
phenomenon these are considered natural
phenomena because naturally, some part of the
Pacific Ocean changes its temperature
commonly occur on average every three to five
years. El Niño happens when the Pacific Ocean
warms temperature, which is why it is
commonly associated with having no rain, dried
up fields, and drought.

Question 4

B. La Niña

Answer 4

• commonly associated with flooding, heavy
  rainfall, and happens when the Pacific Ocean’s
  temperature cools down. It is also the season
  where we experience typhoons with a large
  amount of rainfall, causing widespread flooding
  and other flood related hazards.

Question 5

C. Tropical Cyclone

Answer 5

• Rotating, organized system of clouds and
  thunderstorms that originates over tropical or
  subtropical waters with a minimum sustained
  wind velocity of 35 kilometers per hour (kph)

Question 6

Categories of Tropical Cyclones Speed of Maximum
Sustained Wind

Answer 6

Tropical Depression
35-63 kilometers per hour(kph)

Tropical Storm 64kph- 117 kph

Typhoon 117 kph – 180 kph

Super-typhoon More than 180 kph

Question 7

Public Storm Warning Signal: #1

Answer 7

Meaning: A tropical cyclone will affect the locality,
Winds of 35 up to 60 kph maybe extended up to at least
36 hours
What to do: Listen to the radio for more information
about the weather. Check the capacity of the house to
withstand strong winds and strengthen the house if
necessary.

Question 8

Public Storm Warning Signal: #2

Answer 8

Meaning: A moderate tropical cyclone will affect the
community. Winds of more than 60 to 100 kph maybe
extended in at least 24 hours
What to do: Special attention should be given to the
latest position, the direction, and speed of the movement
as it may intensify and move towards the locality. The
general public, especially people traveling by sea and air
are cautioned to avoid unnecessary risk. Secure
properties before the signal are upgraded. Board up the
window or put a storm shutter in place and securely
fasten. Stay at home.

Question 9

Public Storm Warning Signal: #3

Answer 9

Meaning: A strong tropical cyclone will affect the
locality. Winds of more than 100 kph to 185 kph maybe
extended at least 18 hours
What to do: Keep your radio on and listen to the latest
news about the typhoon. Everybody is advised to stay
indoors. People are advised to stay in a strong building.
Stay away from coastal areas and riverbanks. Watch out
for the passage of the “eye wall” and “eye” of the
typhoon.

Question 10

Public Storm Warning Signal: #4

Answer 10

Meaning: A very intense typhoon. Winds of more than
185 kph may be extended in at least 12 hours.
What to do: Stay in a safe house or evacuation center.
The situation is potentially very destructive to the
community. All travels and outdoor activities should be
canceled. Overall damage to affected communities can
be very heavy.

Question 11

Flood

Answer 11

• Temporary overflow of water onto land that is
  normally dry.

Question 12

Types of flood

Answer 12

• River flood – overflowing of rivers
  when the run-off exceeds the capacity of
  the channels.
• Flash Flood – rapid flooding of
  low-lying areas characterized by raging
  torrents.
• Coastal flood- occurs when strong winds
  push the water inland.

Question 13

• Man-made causes:

Answer 13

• Increased urbanization development.
• Informal settler.
• Indiscriminate dumping of garbage.
  Deforestation.
• Failure of levees and Dams

Question 14

PAGASA’s Color-Coded Warning Signals:

Question 15

Yellow

Answer 15

MONITOR weather conditions. Heavy rain
(7.5-15 mm) is expected, and flooding is possible.
People should be vigilant and monitor weather updates.

Question 16

Orange

Answer 16

ALERT for possible danger and evacuation.
Intense rain (15-30 mm) is expected, and flooding is
likely. People should prepare for possible evacuation,
especially those in low-lying areas.

Question 17

RED

Answer 17

EVACUATE due to high potential of danger.
Torrential rains (above 30 mm) are expected, and serious
flooding is imminent. Evacuation is necessary for safety.

Question 18

E. Storm Surge

Answer 18

• Sudden rise of sea level above the normal level
  on the coast due to a drop in atmospheric
  pressure and the force of the wind as tropical
  cyclone/hurricane approaches the coast.
• The Stronger the cyclone and the shallower the
  coast the higher the surge.
• The peak of the surge is experienced near the
  point of the landfall of the typhoon or storm

Question 19

Causes

Answer 19

• Wind/Pressure effect. The stronger the
  wind of the tropical cyclone and the
  lower the atmospheric pressure, the
  higher the storm surge.
• Rainfall effect. Heavy rain associated
  with an intense tropical cyclone add to
  the total sea level near the coast.
• Shape of the coastline and slope of the
  sea bed. The shallower the slope, the
  higher the surge to the coastal
  communities.

Question 20

Tornado

Answer 20

• Violently rotating column of air that extends
  from a thunderstorm to the ground. Commonly
  characterized by its funnel shape and known as a
  twister, a tornado usually forms when warm,
  humid air collides with cold, dry air and destroys
  everything along its path.
• Can be predicted through the use of Dopler
  radar, but the people must be on the lookout for
  precursory signs. These include the following:
• The appearance of a funnel-shaped column from
  the base of the cumulonimbus cloud
• Having weather that feels warm, humid
• Lightning and thunder
• Roar and buzzing sound of the tornado as it
  reaches the ground.

Question 21

G. Drought

Answer 21

• Commonly attributed to El Niño, drought is the
  lack or insufficiency of rain for an extended
  period that causes a considerable hydrologic or
  imbalance and, consequently, water shortages,
  crop damage, streamflow reduction, and
  depletion of groundwater and soil moisture.

Question 22

H. Wildfire

Answer 22

• Uncontrolled fire that burns in the wildland
  vegetation, often in rural areas. Wildfires can
  burn in forests, grasslands, savannas, and other
  ecosystems, and have been doing so for
  hundreds of millions of years.