DRR Chapter 6 - Hydrometeorological Hazards PDF

CHAPTER 6 HYDROMETEOROLOGI CAL HAZARDS BERNIE C. PALACIO, LPT Objectives: At the end of this lesson, students should be able to: 1. Identify various hydrometeorological hazards. 2. Discuss the reasons why different hydrometeorological hazards take place. 3. Analyze the effects of the differen...

CHAPTER 6 HYDROMETEOROLOGI CAL HAZARDS BERNIE C. PALACIO, LPT Objectives: At the end of this lesson, students should be able to: 1. Identify various hydrometeorological hazards. 2. Discuss the reasons why different hydrometeorological hazards take place. 3. Analyze the effects of the different hydrometeorological hazards; and 4. Execute the prescribed precautionary measures before, during and after each hydrometeorological event.  TYPES OF HYDROMETEOROLOGICAL 1. Typhoons HAZARDS 2. Storm surges 3. Thunderstorms 4. Flooding 5. The El Niño Southern Oscillation (ENSO) Cycle--- El Niño and La Niña  Typhoons Derived from the Chinese word Tai fung, which is broken down into “ta” means big and “fung” means wind. Is a severe weather disturbance characterized by strong winds and heavy rains which revolve around a central low pressure area.  TROPICAL CYCLONE STRUCTURE 1. Eye --- the area of lowest atmospheric pressure in the structure of a tropical cyclone. 2. Eye wall- the region immediately surrounding the tropical cyclone’s center and which can reach as high as 15km above mean sea level, brings the strongest winds, heavy rains and turbulence shortly after the passage of the eye. 3. Rain bands– are spiraling strips of clouds in the fringes of tropical cyclones which are associated with rainfall. TROPICAL CYCLONE STRUCTURE HOW DO TROPICAL CYCLONES FORM? Categories of tropical cyclones  Tropical depression– wind speed up to 61 kph.  Tropical storm– wind speed 62-88 kph.  Severe Tropical Storm – wind speed 89-117 kph.  Typhoon– wind speed -118-220 kph.  Super typhoon– wind speed exceeding 220 kph.  Effects of tropical cyclones Strong winds. Storm surge. Heavy rains.  Measures for mitigating the destructive effects of typhoons 1. Determining areas prone to typhoon-related disasters. 2. Implementing legislation involving land use planning, zoning and building standards. 3. Weather forecasting and monitoring. 4. Effective public typhoon warning systems.  Effective public typhoon warning systems 1. PSWS #1--- Tropical cyclone winds from 30-60km/h are expected within the next 36 hours. Its winds not expected to bring damage but may bring very light damage. 2. PSWS #2--- Tropical cyclone winds of 61km/h to 120km/h are expected within the next 24 hours. Light to moderate damage. 3. PSWS#3--- Tropical cyclone winds of 121km/h to 170km/h are expected within the next 18 hours. Moderate to heavy damage. 4. PSWS#4--- Tropical cyclone winds of 171km/h to 220km/h are expected within 12 hours. Heavy to very heavy damage. 5. PSWS#5--- Tropical cyclone winds of more than 220km/h are expected within 12 hours. Very heavy to widespread damage. STORM SURGE Storm surge defined - A localized unusual increase of sea water level beyond the predicted astronomical tide level primarily due to intense winds and lowered atmospheric pressure during the passage of an intense tropical cyclone from the sea to the land.  Factors that influence the build- up of water level during a storm surge 1. Storm intensity (Wind speed) 2. The pressure effect 3. Size 4. Storm forward speed 5. Angle of approach to coast 6. The effect of earth’s rotation.  Factors that influence the build- up of water level during a storm surge 7. The rainfall effect 8. Geometry of coastal area (Bathymetry refers to the appearance of the ocean or sea bottom resulting from the variation in depth in different portions. Topography is a land configuration resulting from variation in elevation. Shape of the coastline and local features)  Factors that influence the build- up of water level during a storm surge 9. Timing Storm Surge Risk-Reduction Measures 1. Storm surge prediction, hazard map preparation and zoning. 2. Construction of storm surge barriers. 3. Wetland protection.  What to do in the upcoming storm surge?  Keeplistening to official warnings of storm surges issued by PAGASA through television or radio. Make sure to always have batteries and flashlights prepared.  Find the nearest safe high ground where you can evacuate.  When evacuating, bring with you only what is important and essential.  Yourplanned route of evacuation must avoid streams, drainage systems, or any conduits of water as flashfloods can occur and can be life-threatening. THUNDERSTORM Thunderstorm defined A violent, transient type of weather disturbance associated with thousands of meters tall cumulonimbus clouds and which usually involves lightning and thunder, strong winds, intense rainfall and occasionally tornadoes and hail.  Requirements in the formation of thunderstorm  Moisture(water vapor) which must be readily available in the lower atmosphere to produce clouds and precipitation during storm formation.  An unstable, rapidly rising mass of warm air; and A strong upward current of air to force moisture to higher, colder levels of the atmosphere. Stages of life of a thunderstorm  Developing stage– begins with the upward growth of a cumulus cloud due to the continuous updraft and supply of moisture.  Maturestage– indicated by the initiation of strong downward current of air and by precipitation.  Final or dissipating stage– when the updrafts are prevented by the cool air of the dominant downdrafts in the lower portions of the cloud.  Lightning and thunder defined Lightning is? Thunder is?  The abrupt, natural,  The acoustic effect of sudden visible high-voltage expansion of air caused by the electrical discharge heat released during a lightning takes place when strike. positive and negative  Lighttravels at a rate of 3x108 charges join within a m/s while sound travels only at cloud, between clouds a rate of 344 m/s. or between a cloud and the ground. Effects of lightning strike to humans  Lightning strike could directly cause harm to people through contact between the main lightning channel or its branches and the person’s body or a conductor the person is touching.  Lightning strike could also directly cause either blunt force trauma to a person thrown by a shock wave or hearing damage due to thunder or electrical interferences to gadgets they are using like phones, headphones and hearing aids.  Lightning strike may also cause injuries/casualties through secondary effects like explosions and fires.  Lightning safety rules  Danger indoors– While inside a building, avoid staying nearby and watching the lightning through windows or glass portions of doors. It may shatter glass during thunderstorms and cause serious injuries. Glass is an insulator, lightning could hit the person on the side of the window.  Danger outdoors– When seeking shelter, avoid open vehicles and small unenclosed structures while steel waiting sheds and wooden huts. Did you know??  When your hair begins to stand up during a thunderstorm, it could be an indication that positive charges from the ground are flowing through you to get to the negative charges in the thunderstorm clouds. That is a warning for you to immediately seek shelter indoors because you are at a risk of getting struck by lightning. Effects of lightning on infrastructure, technology and environment  Infrastructure  Technology  Trees and forest fires  Acid rain Hail  Hailis a type of solid precipitation. Hailstone is the individual piece of layered, rounded or irregularly-shaped ice which is occasionally produced during a thunderstorm.  The diameter of hailstone can be as small as 1mm and as large as 20mm. Hail formation  Hailstonesare formed when a high amount of moist warm air ascends very quickly into thunderstorm clods with a large proportion well above the freezing level.  The water droplets from condensation reach the freezing level so fast and are almost instantaneously frozen. Hail formation  The tiny ice crystals which are initially formed, drift up and down repeatedly due to strong upward current of air and accumulate more ice until such point that the weight of the ice crystals surpasses the force exerted by upward air currents. Factors favoring hail  Lower temperature  Strongerupdrafts caused by horizontal winds that tend to be forced upward upon hitting mountains.  Shorterdistance between the clouds and the high grounds which delays melting of hailstone. Tornadoes and waterspouts  Tornadoes are narrow, funnel-or cylindrical- shaped, and intensely-rotating columns of wind that form during powerful thunderstorms and extend from the base of a cumulonimbus cloud down to the earth’s surface.  Waterspouts basically the same as tornadoes, the only difference is that the rotating column of wind moves over a body of water. Tornadoes and waterspouts formation  When warm, moist winds and cool, dry winds coming from different directions with different speeds meet, instability occurs in the lower atmosphere.  When the wind direction changes and wind speed increases with increasing height, an invisible, horizontal spinning effect takes place in the lower atmosphere. Tornadoes and waterspouts formation  An updraft supplying more warm and moist air to the thunderstorm causes the horizontally spinning air wind to tilt and eventually stand vertically. Safety tips  According to NOAA (National Oceanic and Atmospheric Administration), during a tornado, the most important thing to keep in mind to survive or avoid getting hurt is the phrase: “Get in, get down, and cover up.” Safety tips  According to NOAA (National Oceanic and Atmospheric Administration), during a tornado, the most important thing to keep in mind to survive or avoid getting hurt is the phrase: “Get in, get down, and cover up.” Downburst  Are relatively small, localized sources of violently descending strong winds that travel along straight line paths during thunderstorms. Downburst Flashflood  Severe, slow-moving thunderstorms pour a large amount of precipitation over a very limited areal extent.  It occurs when rain falls on a low-lying area where there is low infiltration and where natural and man-made drainage channels may not have enough capacity to allow large amount of runoff to flow out of the area with ease. FLOODING What is flooding?  Itis the abnormal rise of water levels in rivers, coastal areas, plains, and in highly urbanized centers which may be a result of natural phenomena, human activities, or both. Primary Flood Types and Causes Riverine - The rate of increase of water level is dependent on the river type and source of additional water input. Extreme and sustained rainfall - Large amount of precipitation can cause flooding, simply because the volume of water input can sometimes be too much for the capacity of rivers to drain the water and for the ground to absorb the water. Primary Flood Types and Causes Estuarine and coastal - It occurs when seawater encroaches low-lying land that is usually still above sea level. - Flooding can cause unusually high tides namely: Astronomical high tide. Primary Flood Types and Causes Astronomical high tide - A short-term sea level rise caused by the gravitational pull of the moon and the sun on the earth’s waters. - Types of tides namely: Spring tide and Neap tide. Spring tide – it happens when the sun, earth, and the moon are aligned during new moon and full moon and cause water to bulge in the direction of the alignment. Primary Flood Types and Causes Neap tide – it occurs during quarter moons, do not cause extreme tides because the gravitational pull of the moon and the sun are perpendicular to each other and cancel each other out. Urban flooding - It occurs in highly populated, developed areas set on relatively low-lying areas like valleys and plains. - Urban flooding is largely as a result of: Saturation of the ground due to too much rainfall, and the presence of large areas of impermeable surfaces like concrete pavements and rooftops. - Urban flooding is largely due to man-made causes. It may be due to lack of proper drainage systems. Catastrophic flooding and flash flood - It is a result from ground failure and/or major infrastructure failure. - Flashflood is a rapid, short-lived, and violent arrival of a large volume of water which can be caused by intense localized rainfall on land that is saturated or unable to absorb water. Destructive effects of flooding Primary effects – loss of lives and damage to amenities and loss of access to basic necessities. It include damage to infrastructure such as houses, commercial buildings, bridges, roads, transportation facilities, drainage and sewerage disposal systems, power generation and/or transmission facilities, water supply and treatment facilities and farm land. Destructive effects of flooding Secondary effects – are the short-tem, immediate, but indirect consequences of flooding include: power loss, domestic and potable water loss/shortage, risk of acquiring waterborne diseases, usually due to mixing of human sewage with flood waters, difficulty of mobilization due to damage to transportation facilities, and, food shortage. Destructive effects of flooding Tertiary effects – long-term indirect consequences of flooding: economic hardships at the local and national levels and unemployment, additional government expenditures on rehabilitation of public infrastructure. What to do before, during and after a flood? Long Before the flood - Find out If your area is prone to flooding on existing flood maps prepared by MGB. Have an accessible emergency flood kit always prepared which contains flashlight, batteries, first aid kit, radio, clothes, blankets, towels, bottled water, and ready-to-eat food. What to do before, during and after a flood? Before an impending flood - Keep tuned in to the news on television and radio for weather updates, flood warning, and evacuation alerts. Gather or call all family members and/or persons in your household to inform them of the impending flood so that they could accordingly plan their activities for the day. Also, try to get very important and delicate personal property to higher grounds to avoid damage. What to do before, during and after a flood? During the flood - As much as possible, avoid having to walk or drive through floodwaters. Also, make sure to wear boots to avoid getting electrocuted. Turn off gas lines or cooking gas tanks, shut down electricity from control panels to avoid any possible electrocution and turn off water gauge valve to prevent any possible harm/damage and potential costs if left unmonitored during evacuation. What to do before, during and after a flood? After the flood - Take precautions against risk in entering property that may have been structurally compromised and contaminated. If water has not entirely subsided, make sure to still wear boots to avoid getting electrocuted. Then, if possible document the damage to your property by taking pictures and describing these in detail.  THE EL NIÑO SOUTHERN OSCILLATION CYCLE EL NIÑO AND LA NIÑA The ENSO is a natural climatic phenomenon characterized mainly by cyclic fluctuation of warm and cold sea surface temperatures and atmospheric pressure in the central and eastern equatorial pacific. The term ENSO came into use in the year 1960 after regional variation in sea surface temperatures was observed to coincide with atmospheric pressure variations between the eastern and western tropical pacific. EL NIÑO - Is a prolonged unusual warming of sea surface temperatures in the central equatorial pacific and the eastern equatorial pacific. It entails a 3-month, greater-than-usual warming in a specific portion of the east-central tropical pacific ocean. Cause of EL NIÑO - Wind is usually blown to the west along the equator in the Pacific region which causes the piling of water that can reach up to half a meter in the Western Pacific. In the Eastern portion of the Pacific, upwelled, deeper, and colder water replaces the insolated surface water that has been pushed west. Effects - Effects on domestic water supply, irrigation, and electricity generation. - Agriculture. - Effects on marine ecosystem, capture fishery, and aquaculture. - Land degradation - Water quality deterioration - Forest wildfires - Land Subsidence - Direct economic and societal effects. LA NIÑA - It involves prolonged unusual cooling of sea surface temperatures in central and eastern equatorial pacific that may last for 1-3 years. Cause - It is caused by the strengthening of the easterly trade winds which blow more warm water toward the west and allows the upwelling of cold water in the east. Effects - It causes near to normal above normal rainfall conditions, particularly over the eastern sector of the country. - It also leads to the increase of the number of tropical cyclones that enter the Philippine Area of Responsibility that shifts toward the western pacific ocean. Effects - It causes near to normal above normal rainfall conditions, particularly over the eastern sector of the country. - It also leads to the increase of the number of tropical cyclones that enter the Philippine Area of Responsibility that shifts toward the western pacific ocean.