Understanding Hydrometeorological Hazard

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HydroMetHazard Mt. Province


First let’s dissect the words and explain their definition:

Hydrometeorology: it’s a branch of meteorology and hydrology that studies the transfer of water and energy between the land surface and the lower atmosphere.

Hazard: any source that can cause harm or damage to humans, property or the environment.

Hazard and risk are often used intertwined, but they are in fact different. Risk is defined as the probability that exposure to a hazard will lead to a negative consequence.

Definition hydrometeorological hazards

When you look up the definition of hydrometeorological hazards you will find: “Process or 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”.

The hazards you can think of are tropical cyclones (typhoons and hurricanes), thunderstorms, hailstorms, tornados, blizzards, heavy snowfall, avalanches, coastal storm surges, floods including flash floods, drought, heatwaves and cold spells.

Extreme weather

Due to global warming climate change these natural hazards are expected to increase. These extreme weather events have a high impact on the world. According to Unesco these three hydrometeorological hazards have one of the highest impacts:

Floods: they affect every country, and cause more fatalities and more property damage than any other type of hazard. Not only does it cause injuries and deaths, floods can disrupt water purification and sewage disposal systems, and can cause toxic water waste sited to overflow.

Hurricanes, cyclone and typhoons: these are severe storms that form over tropical water. Windstorm-related events worldwide cause an average of 30,000 deaths and US$2.3 billion in damage each year.

Droughts: while floods and storms are often sudden, droughts are slow events that can cause large agro-ecological damage and seriously disrupt socio-economic life.



Hydrometeorological Hazards

1. Hydrometeorological hazards are processes or phenomena of atmospheric, hydrological or oceanographic nature • may cause loss of life, injury or other health impacts, property damages, loss of livelihoods and services, social and economic disruptions, or even environmental damages Hydrometeorological Hazards...

2. Hydrometeorological hazards include:












-BLIZZARDS Hydrometeorological hazards...

3. Hydrometeorological conditions also can be a factor in other hazards such as landslides, wild fires, locust plagues, epidemics, and volcanic eruptions. Hydrometeorological hazards...

4. The following are the most common Hydrometeorological hazards as defined by the National Oceanic and Atmospheric Administration (NOAA):


5. A cyclone is an intense low pressure system which is characterized by strong spiral winds towards the center, called the “Eye” in a counter-clockwise flow in the northern hemisphere. Hazards due to tropical cyclones are strong winds with heavy rainfall that can cause widespread flooding/flash floods, storm surges, landslides and mudflows.

6. Classification of Cyclone: Tropical Depression – maximum winds from 35 kilometers per hour (kph) to 63 kph Tropical Storm – maximum winds from 64 kph to 118 kph Typhoon – maximum winds exceeding 118 kph

7. A typhoon is a large, powerful and violent tropical cyclone. It is a low pressure area rotating counter-clockwise and containing rising warm air that forms over warm water in the Western Pacific Ocean. Less powerful tropical cyclones are called Tropical Depression and Tropical Storms.

8. A typhoon is called a hurricane in the Atlantic Ocean, a cyclone in Indian Ocean and wily- wily in Australia. Typhoons can inflict terrible damage due to thunderstorms, violent winds, torrential rain, floods, landslides, large and very big waves associated with storm surges.

9. A thunderstorm is a weather condition that produces lightning and thunder, heavy rainfall from cumulonimbus clouds and possibly a tornado. It is a violent local disturbance accompanied by lighting, thunder and heavy rain and often by strong gust of wind, and sometimes by hail.

10. The typical thunderstorm caused by convection occurs when the sun’s warmth has heated a large body of moist air near the ground. This air rises and called by expansion. The cooling condenses the water vapor present in the air, forming a cumulus cloud.

11. • a tornado is described as a violent rotating column of air extending from thunderstorm to the ground • tornadoes come in many sizes • are typically in the form of a visible condensation-funnel which is narrow and touches the earth • is often encircled by a cloud of debris

12. • have a wide- range of colors depending on the environment • typically, may appear nearly transparent and invisible until dust and debris are picked up • develop from severe thunderstorms in warm, unstable air along and ahead of cold fronts

13. A flash flood is a rapid flooding of geomorphic low-lying areas like washes, rivers, dry lakes and basins. Common causes of flash flood:  heavy rain with a severe thunderstorm  tropical storm  melt water from ice  snow flowing over ice sheets or snowfields  hurricane

14. • flash floods may occur after the collapse of a natural ice or debris dam, or a human structure such as man-made dam • flash Floods are distinguished from regular floods by a timescale of less than six hours

15. Flood is the inundation of land areas which are not normally covered by water. A flood is usually caused by a temporary rise or the over- flowing of a river, stream, or other water course, inundating adjacent lands or flood-plains.

16. • temporary rise of lakes, oceans or reservoirs and/or other enclosed bodies of water • heavy and prolonged rainfall associated with tropical cyclones, monsoons, inter-tropical convergence zones or active low pressure areas • debris jam causes a river or stream to overflow and flood the surrounding area.

17. Floods are basically HYDROLOGICAL PHENOMENA caused by storm surges, and tsunami along coastal areas Two key elements are rainfall intensity and duration. Intensity is the rate of rainfall, and duration is how long the rain lasts.

18. Storm surge is the rise of the seawater above normal sea level over the coast, generated by the action of weather elements such as cyclonic wind and atmospheric pressure. Sea level is raised and driven towards the coast. Where the depth is shallow and the slope of the sea bed is gradual, the natural flow of water is delayed by the effect of friction on the sea bed.

19. As more water moves from the sea to the coast excess water piles up on the shore line. This pilling up of water makes a large volume of water which might eventually flow into hinterland some distance from the coast. Depending upon the shape of the coastline and the slope of the sea bed, storm surge can sweep across large portions of coastal areas.

20. El Niño and La Niña are complex weather patterns resulting from variations in ocean temperature in the equatorial pacific. These two phenomena are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle.

21. The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and the atmosphere in the East-central Equatorial Pacific (approximately between the International Date Line and 120 degrees West).

22. La Niña is sometimes referred to as the cold phase of ENSO and El Niño as the warm phase of ENSO. These deviations from normal surface temperatures can have large-scale impacts not only on ocean processes, but also on global weather and climate.

23. El Niño and La Niña episodes typically last nine to 12 months, but some prolonged events may last years. While their frequency can be quite irregular, El Niño and La Niña events occur on average every two to seven years. Typically, El Niño occurs more frequently than La Niña.

24. The general sequence of events that could occur during the development of a Category 2 typhoon/hurricane (wind speed 96-110 mph) approaching a coastal area: (Herald Tribune, 2011)

25. 96 hours before landfall: At first there aren’t any apparent signs of storm. The barometer is steady, winds are light and variable, and fair-weather cumulus clouds appear.

26. 72 hours before landfall: Little has changed, except that the swell on the ocean surface has increased to about six feet and the waves come in every nine seconds. This means that the storm, far over the horizon, is approaching.

27. 48 hours before landfall: The sky is now clear of clouds, the barometer is steady, and the wind is almost calm. The swell is now about nine feet and coming in every eight seconds.

28. 36 hours before landfall: The first signs of the storm appear. The barometer is falling slightly, the wind is around 11 mph, and the ocean swell is about 13 feet and coming in seven seconds apart.

29. On the horizon, a large mass of white cirrus clouds appear. As veil of clouds approaches, it covers more of the horizon. A hurricane watch is issued, and areas with long evacuation times are given the order to begin.

30. 30 hours before landfall: The sky is covered by a high overcast. The barometer is falling at .1 millibar per hour; winds pick up to about 23 mph. The ocean swell, coming in five seconds apart, is beginning to be obscured by wind- driven waves and small whitecaps begin to appear on the ocean surface.

31. SATELLITE- is the most advance technology used in monitoring a cyclone or typhoon. It can visualize exactly in real time the formation and the path of a cyclone.

32. Doppler RADAR is an acronym for Radio Detection and Ranging. Radar detection devices emit and receive radio waves to determine the distance from the source to the object by measuring the time if it takes for the echo of the wave to return.

33. Specifically, weather radar measures the direction and the speed of moving objects, such as precipitation, and has a capacity to measure the velocity of the particles in order to determine the rate of which the particles are falling.


35. Preparedness and Mitigation

36. The following preparedness and mitigation strategies are adopted from the Department of Education’s Disaster Risk Reduction Resource Manual issued on 2008:

37. Preparedness (What to do before): • Establish and maintain coordination with Barangay Disaster Coordinating Councils (BDCC) and personnel. • Ensure that house can withstand heavy rain and strong winds.

38. • Learn more about typhoon and other weather disturbances, their signs and warnings, effects and dangers and how to protect house and other properties. • Learn something relevant to mitigation and preparedness for tropical cyclones. • Participate actively to school’s disaster response-drill or simulation.

39. Response (What to do during): • Monitor through radio or other reliable sources the latest official report of PAGASA on the typhoon. • When house is no longer safe, evacuate immediately to safer place

40. • Stay indoors and away from windows. • Keep an open line of communication. with relatives that are not affected to keep them posted. • Ensure that members of the family will remain calm by keeping them informed of the latest developments.

41. Rehabilitation (What to do after): • Help in attending the victims immediately. For minor cuts and wounds apply first aid. • In case of major cuts and wounds, seek necessary medical assistance at disaster station or hospital.

42. • Help in checking the house for damages and losses. Note damages that require immediate repair, e.g. electrical connections and water supply. • Coordinate with Barangay officials and LGU’s for assistance.

43. Preparedness (What to do before): Develop a Family Preparedness Plan In case of severe thunderstorm – specific planning should include the following:

44. • Learn more about your area’s severe thunderstorm risk. • Discuss how you would know if a thunderstorm may produce a tornado. • Discuss how to be warned of an approaching thunderstorm.

45. • Recommend trimming and removal of dead or rotting trees that could fall and may cause damage or injury. • Secure outdoor objects that could be blown away and cause damage. • Secure house doors and windows both from the inside and outside.

46. • Learn how to estimate the distance of the thunderclouds by computing the difference in time(second) between seeing the flash of lightning and hearing the claps of thunder. (1 second = 1000 ft.).

47. Response (What to do during): • Learn to do the lightning safety position and stay away from structures, trees, towers, fences, telephone lines, or power lines if out in the open. • Carefully watch out for falling debris and flash floods.

48. • Stay calm throughout the occurrence of thunderstorm. • Postpone all outdoor activities. • Avoid plumbing and bathroom fixtures that are good conductors of electricity.

49. • Unplug or turn off all appliances and other electrical items such as computers. • Turn off air conditioner and television and stay off the phone until the storm is over. Use a battery operated radio for gaining information.

50. • Choose and move to a ‘safe place’ in your house (if there is any) where members of the family can gather together during a thunderstorm preferably on lowest floor of your house. Where there are no windows, skylights, or glass doors, which could be broken by strong winds or hail, causing damage or injury.

51. “Lightning safety experts have invented a ‘lightning safety position’ that is very important to know if you are caught in a thunderstorm and you can’t find a shelter. FOLLOW THE LIGHTNING SAFETY POSITION for:  It makes you a smaller target

52. With your heels together,if lightning hits the ground, it goes through the closest foot, up to your heel and then transfers to the other foot and goes back to the ground again. If you don’t put your feet together, lightning could go through your heart and kill you. You put your hands over your ears to protect them from thunder.” (Lightning Safety Experts)

53. Preparedness (What to do before): • Develop a preparedness plan for the whole family. • Have periodic drills with the members of the family. • Inspect pre-designated areas to ensure the best protection.

54. • Keep an open line communication with other members of the family. • Listen to radio and television for information. • Store flashlights and back-up batteries to receive warnings reponse.

55. Response (What to do during): • Move to pre-designated area or an interior room on the lowest floor and get under a sturdy piece of furniture. • Stay away from windows. • Lie flat in a depression if caught outside your house/ school or any building.

56. Rehabilitation (What to do after): • Attend to survivors immediately. • Check the house for damages and losses. • Coordinate with proper authorities for assistance.

57. Preparedness (What to do before): • Find out the frequency of occurrence of floods in locality, especially those that affect your area. • Know the flood warning system in your locality. If none exists, recommend to the appropriate authority for the creation of one.

58. • Research from previous occurrences how fast the water floods occur in your area and how it rises. • If it has been raining hard for several hours, or steadily raining several days, be alert to the possibility of a flood. Floods happen as the ground becomes saturated.

59. • Watch out for rapidly rising water and help prepare the family for evacuation. • Switch off the electricity and lock the rooms after all have gone out. Have a handy survival kit. It should contain battery operated transistor radio,

60. flashlight, emergency cooking equipment, candies, matches, and first aid kit. • Use a radio or a portable, battery-powered radio (or television) for updated information. Local stations provide the best advice for your particular situation.

61. Response (What to do during): • Stay calm and keep updated with the status of the situation and safety reminders on what to do and where to go in case of evacuation. • Listen continuously to a radio, or a portable, battery-powered radio (or television) for updated emergency information.

62. • Do not attempt to cross flowing streams unless assured that the water is below knee high level. • Avoid areas prone to flash flooding and be cautious of water- covered roads, bridges, creeks and stream banks and recently flooded areas.

63. • Do not go to swimming or boating in swollen rivers. • Watch out for snakes in flooded areas. • Eat only well-cooked food and drink only clean or preferably boiled water and throw away all food that has come into contact with flood water.

64. Rehabilitation (What to do after): • Report broken utility lines (electricity, water, gas, etc.) immediately to appropriate agencies/authorities. • Ensure that electrical appliances are checked by a competent electrician before switching them on.

65. • Avoid affected areas. • Continue to listen to a radio or local television stations and return home only when authorities indicate it is safe to do so. • Stay away from any building that is still flooded.

66. Preparedness (What to do before): • Know the storm surge risk zones and identify safer grounds for relocation if necessary. • Ensure that everyone is familiar with the identified escape routes of the family to higher grounds.

67. • Stay off the beach when weather disturbance exists. • Help establish evacuation plans and procedures. • Participate in the regular conduct of drills and exercises.

68. Response (What to do during): • Immediately move to higher grounds upon detection of signs of a probable storm surge or upon receiving a warning that a storm surge is eminent. • Be alert of and stay away from steep, high coastal areas which are prone to landslides.

69. • Switch off power supply. • Stay on the on the inland side away from the potential flow of water. • If caught in a storm surge, take hold of large boulders or tree trunks which can provide protection from the force of water or debris carried by the flowing water.

70. Rehabilitation (What to do after): • Do not eat fresh food that came in contact with flood waters. • Drinking water should be submitted to proper authorities for testing. • Check damage of the house to ensure that there is no danger of collapse.

71. • Check house for electrical damage and open live wires. Electrical fixtures should only be switched on after making sure that is safe to do so. • Help clean all mud and debris immediately.

72. The following are examples of hydrometeorological hazard maps.

73. PROJECT NOAH by the department of science and technology(DOST) - a project for scientific forecasting, monitoring, assessment and information services regarding natural hazards - a more accurate, integrated, and responsive disaster prevention and mitigation system, especially in high-risk areas throughout the Philippines

74. Project NOAH (Nationwide Operational Assessment of Hazards) The project will harness technologies and management services for disaster risk reduction activities offered by the DOST through PAGASA, PHIVOLCS, and the DOST- Advance Science and Technology Institute (ASTI), in partnership with the UP National Institute of Geological Sciences and the UP College of Engineering.

75. The Project has the following components: 1. Distribution of hydrometeorological devices in hard-hit areas in the Philippines (Hydromet). A total of 600 automated rain gauges (ARG) and 400 water level monitoring stations (WLMS) will be installed along the country’s 18 major river basins (RBs) by December 2013 to provide a better picture of the country’s surface water in relation to flooding.

76. 2. Disaster Risk Exposure Assessment for Mitigation – Light Detection and Ranging (DREAM-LIDAR) Project. The project, which is targeted to be completed by Dec. 2013, aims to produce more accurate flood inundation and hazard maps in 3D for the country’s flood-prone and major river systems and watersheds.

77. 3. Enhancing Geohazards Mapping through LIDAR. The project which is targeted to be completed by December 2014, shall use LIDAR technology and computer-assisted analyses to identify exact areas prone to landslides.

78. 4. Coastal Hazards and Storm Surge Assessment and Mitigation (CHASSAM). CHASSAM, which is targeted to be completed by December 2014, will generate wave surge, wave refraction, coastal circulation models to understand and recommend solutions for coastal erosions.

79. 5. Flood Information Network (floodNET) Project. Targeted to be complete by December 2013 is the flood center that will provide timely and accurate information for flood early warning systems. The FloodNET Project will come up with computer models for the critical RBs, automate the process of data gathering, modelling and information output, and release flood forecasts.

80. 6. Local Development of Doppler Radar Systems (LaDDeRS). LaDDeRS seek to develop local capacity to design, fabricate, and parameters of sea surface such as wave, windfield, and surface current velocity.
81. 7. Landslides Sensors Development Project. This project is a low cost, locally developed, sensor based early monitoring and warning system for landslides, slope failures, and debris flow. As of May 2012, 10 sensors have been installed in:

82. San Francisco, Surigao del Norte; Tago, Surigao del Sur; Tublay, Buguias, and Bokod in Benguet; Guihulngan City, Negros Occidental; St. Bernard, Southern Leyte; and Tubungan, Iloilo. Additional sensors are expected to e deployed to not less than 50 sites by 2013.

83. 8. Weather hazard Information Project (WHIP). WHIP involves the utilization of platforms such as television (DOSTv) and a web portal (http://noah.dost.gov.ph), which display real-time satellite, Doppler radar, ARG and WLMS data to empower LGUs and communities to prepare against extreme natural hazards. This is complimented by activities, such as:

84. a) conducting IEC (Information, Education, and Communication) activities; b) the processing and packaging of relevant and up-to-date information for public use.