HYDROMETEOROLOGICALHAZARD_STORM SURGE.pptx

Types of Hydrometeorological Hazards

1. STORM SURGE PRESENTED BY: ANTONETTE BONIEL

2. A storm surge is 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 STORM SURGE

3. TSUNAMI Tsunamis literally mean "harbor wave" in Japanese. Strictly speaking this term pertains to a seismic sea wave. Perhaps because people cannot tell apart the devastating effects of tsunami and a storm surge, these terms are often interchanged.

4. TSUNAMI A tsunami however, is a succession of water waves formed in the sea or ocean when an immense volume of water is displaced, possibly due to earthquakes, volcanic eruptions, mass wasting events meteorite impacts, Underwater explosions, or any other onshore and offshore disturbances strong enough to displace a great volume of water toward the land.

5. TSUNAMI STORM SURGE Tsunamis have way longer wavelengths (tens to hundreds of Kilometers). Arrival periods of tsunamis typically range from minutes to hours. compared to storm surges (tens to hundreds of meters) and more so, normal sea waves (several centimeters to a few meters)

6. The tidal wave , on the other hand, which a storm surge is also often erroneously called, is formed due to the imbalanced, gravitational influences of the celestial bodies like the moon, the sun, and other planets. Wavelengths of a tidal wave could be so wide that it may take as much as 24 hours to arrive.

7. FACTORS THAT INFLUENCE THE BUILD-UP OF WATER LEVEL DURING A STORM SURGE 1. Storm Intensity 2. The pressure effect 3. Size 4. Storm Forward Speed 5. Angle of Approach to Coast 6. Effects of Earth's Rotation 7. The Rainfall Effect 8. Geometry of Coastal Area 9. Timing

8. A storm Surge is mainly wind-driven. Storm Intensity, which is related to the wind speed of a storm, has an influence on the amount of surge produced. The force of the wind exerts on the body of water is proportional to the square of wind speed (V²). Therefore, the stronger the winds associated with a tropical cyclone, the higher the storm surge formed. 1. STORM INTENSITY (WIND SPEED)

9. During a tropical cyclone, storm surge level is also influenced by atmospheric pressure. A lower atmospheric pressure results in a higher storm surge level. Lowered atmospheric pressure and wind speed are the major causes of storm surge formation . 2. The Pressure Effect

10. A tropical cyclone with a larger diameter will form a higher surge because the winds brought about a larger tropical cyclones push on a larger surface area of the ocean and affects this are for a longer period of time. As a result of this duration, a greater amount of rainfall is allowed to be dumped over this area. 3. Size

11. A tropical cyclone traveling with a higher velocity will produce a higher surge along an open coast. Conversely, a tropical cyclone traveling with a lower velocity is more efficient in producing a higher and broader storm surge in enclosed and semi-enclosed bodies of water like bays and estuaries 4. Storm Forward Speed

12. The amount of surge formed is affected by the angle by which the tropical cyclone hits the coastline. When a tropical cyclone bits the coast perpendicularly (as opposed to an approach which is parallel or oblique), it will more likely form a higher storm surge because a larger part of the storm surge mound comes into contact with the coastline and is allowed to build up more. 5. Angle of Approach to Coast

13. There is a tendency for ocean currents to be deflected as a result of the earth's rotation. This is called the Coriolis Effect. In the northern hemisphere, currents are bent to the right, while in the Southern hemisphere currents are bent to the left . 6. The Effect of the Earth's Rotation

14. Water levels can rise quickly in estuaries because large volumes of accumulated rainwater from watersheds in higher elevation areas which are drained by rivers encounter waters driven by the tropical cyclone from the open ocean. 7. The Rainfall Effect

15. 8. Geometry of coastal area (bathymetry, topography, coastline shape, and local features) The height of the storm surge which reaches the shore is affected by the bathymetry of the ocean bottom.

16. Bathymetry is the appearance of the ocean or sea bottom resulting from the variation in depth in different portions. Lower surges with higher and stronger waves are formed when the tropical cyclone hits a shoreline bordered by a shelf separated from the open sea by a steep slope.

17. Topography (land configuration resulting from variativation in elevation) also has an influence on storm surge extent. Wide, low-laying areas with elevation of obly few meters above sea level are vulnerable to storm surges.

18. The shape of the Coastline can also affects the behavior of a storm surge. Storm surge level is higher when a tropical cyclone hits a concave coastline. This is because of the funneling effect, which is simply the entrapment in a smaller accommodation space of water being dumped by the strong winds.

19. In addition, man-made and natural local features found within the coastal area may affect the flow of water and the behavior of the storm surge. Sea walls, breakwaters, mangroves, coral reefs, onshore vegetation, sand dunes, and berms, to some extent, may weaken a storm surge

20. 9. Timing As with the occurrence of a lot of other natural phenomena, toming plays an important role. When the formation of a storm sutge during a tropical cyclone coincides with a high astronomical tide, the resulting surge is higher. Also when the surge approaches the coast near the time of the tropical cyclone's maximum winds speed, the surge tends to have a greater inland reach.

21. Potential Damage by a Storm Surge Buildings, roads, bridges, piers, and other infrastructure may not only be submerged, they can also be washed away and destroyed when a storm surge hits an area if they are not strongly rooted in the ground. Cars and almost anything else in the path of the storm surge will surely be drifted very far from their original positions because of the enormous force of the waves driven inland. Saltwater may also contaminate groundwater

22. Storm Surge Risk Reduction Measures 1. Storm Surge prediction, hazard map preparation, and zoning Computer programs employing mathematical models ate now being used go simulate natural processes like storm surges and to predict the potential location and extent of flooding. These require accurate numerical input values to describe parameters like qind speed, tropical cyclone size, atmospheric pressure, place and tome of land fall, tide levels, wave and river flow rate, and the configuration of the coastal area

23. Storm Surge Risk Reduction Measures 2. Construction of Storm Surge Barriers Storm surge Barriers are gate-like, hard engineering structures installed in front of tidal inlets, rivers, and estuaries which are ckosed before impending extreme water level increase, like storm surge . These prevents storm surge form advancing upstream and therefore avoid life-threatening flooding.

24. Storm Surge Risk Reduction Measures 3. Wetland Protection People residing near the coast can minimize the potential damage of a storm surge by making efforts to protect nearby wetlands because the sediments and vegetation found in swamps, estuaries, and mud flats can actually dampen the destructive force of storm surges. As much as possible, development of these areas for housing, industry, or agriculture should be avoided.

25. WHAT TO DO IN THE EVENT OF AN IMPENDING STORM SURGE There is usually an ample amount of time for people to prepare for such an event. If you happen to be near or within a storm surge-prone area, here are several things to keep in mind and make sure you do:

26. WHAT TO DO IN THE EVENT OF AN IMPENDING STORM SURGE 1. During an unusually strong tropical cyclone, keep listening to official warnings of storm surges issued by PAGASA through television or radio. It is convenient to have a radio that runs on batteries. Make sure to always have batteries and flashlights prepared.

27. WHAT TO DO IN THE EVENT OF AN IMPENDING STORM SURGE 2. Find the nearest safe high ground where you can evacuate. An area of high elevation should be identified way ahead of time especially if you are living in a kow lying area, like along the coast or near river channels

28. WHAT TO DO IN THE EVENT OF AN IMPENDING STORM SURGE 3. When evacuating, bring with you only what is important and essential. You do not want to be slowed down by bringing with you so many things.

29. WHAT TO DO IN THE EVENT OF AN IMPENDING STORM SURGE 4. Your planned route of evacuation should avoid streams, drainage channels, and any other conduits of water as flashfloods can occur and can be life-threatening

30. TYPHOON YOLANDA (HAIYAN) LEYTE STORM SURGE TRAGEDYE On November 8, 2013, Typhoon Yolanda (International name: Haiyan) made landfall initially on Guluan , Samar-on the eastern seaboard of the Philippines, and is one of the strongest and deadliest tropical cyclones. According to the Joint Typhoon Warning Center Hawaii, Typhoon Yolanda was characterized by 1 minute sustained speed of 314km/ hr and 10-minute sustained speed of 230 km/hr. However, it already began forming by November 2, 2013 as a low pressure area about 425 kilometers east-southeast of Pohnpei in the Federated States of Micronesia.

31. TYPHOON YOLANDA (HAIYAN) LEYTE STORM SURGE TRAGEDYE What most people were not prepared for was the storm surge which resulted from the landfall of one of the strongest typhoons recorded in history. Flooding was also expected, however, apparently not of the magnitude that inundated the city of Tacloban. This is most likely the reason why evacuees did not seek refuge in an area with high enough elevation.