6.2

• Storm Surge


  When the sea level rises higher than normal because of strong winds and low pressure from a tropical cyclone, mostly happening when a cyclone moves from sea to land

  
• The Philippines is highly prone to storm surges because of its location near the equator in the Pacific region, and due to the extensive length of its coastline
• Factors that influence the buildup of water level during a Storm Surge


  • Storm intensity
  • Pressure effect
  • Size
  • Storm forward speed
  • Angle of approach to coast
  • Effect of the Earth's rotation
  • Rainfall effect
  • Geometry of coastal area
  • Timing

  
• Storm Intensity


  A storm surge is primarily caused by the wind, and the intensity of a storm, determined by its wind speed, affects the magnitude of the surge

  
• Pressure effect


  During a tropical cyclone, the storm surge level is influenced by atmospheric pressure, where a lower atmospheric pressure leads to a higher storm surge level

  
• Size


  A larger tropical cyclone diameter leads to a higher storm surge, as the winds of larger cyclones push on a larger area of the ocean for a longer time

  
• Storm forward speed


  The velocity of a tropical cyclone affects the surge it produces, where higher velocity results in a higher surge along an open coast, while lower velocity creates a higher and broader storm surge in enclosed bodies of water

  
• Angle of approach to coast

  The angle at which a tropical cyclone hits the coastline impacts the surge formed, where a cyclone hitting the coast perpendicularly creates a higher storm surge

  
• Effect of the Earth's rotation

  The Coriolis effect, caused by Earth's rotation, deflects ocean currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, meaning the largest surge will be in the northeast quadrant in the Northern Hemisphere and the northwest quadrant in the Southern Hemisphere
• Rainfall effect


  Water levels in estuaries can rapidly rise due to the convergence of rainwater from higher elevation areas and the influx of ocean waters driven by a tropical cyclone
• Geometry of coastal area

  The height of the storm surge that reaches the shore is influenced by the shape of the ocean floor, where a narrow and steep slope results in a lower surge but stronger waves, while a wide and gentle slope results in a higher surge but smaller waves

  
• Timing


  Timing is crucial in the formation of a storm surge during a tropical cyclone, as when the surge aligns with a high astronomical tide, the surge is higher, and if the surge coincides with the peak wind speed of the cyclone, it tends to reach further inland

  
• Potential Damage by a Storm Surge

  • Flooding
  • Damage to buildings
  • Damage to roads
  • Damage to bridges
  • Damage to piers
• Storm Surge Risk-Reduction Measures

  • Hazard mapping and early warning systems
  • Construction of storm surge barriers
  • Wetland protection

  
• What to Do in the Event of an Impending Storm Surge

  • Stay informed
  • Evacuate to high ground
  • Plan your evacuation route