Hydrometeorological Hazards - STORM SURGE, FLOODING

baejuhyeoned's version from 2017-03-07 21:49


Question Answer
Storm surgeAn abnormal rise of water generated by a storm over and above sea tide level
Surge heightrefers to the height of water above sea level at the time of the storm surge peak
5-6 meters highYolanda storm surge height
(1) Storm intensity (wind speed), (2) Pressure effect, (3) Size, (4) Storm forward speed, (5) Angle of approach to coast5 Factors that affects the build up of water level during storm surge
Storm intensity (wind speed)Storm surge is wind driven
Storm intensity (wind speed)The stronger the winds associated with a tropical cyclone the higher the storm surge formed
Pressure effectLow atmospheric pressure results in high storm surge level
Pressure effectHigher surge levels happens at the center of a tropical cyclone
SizeTropical cyclone with larger diameter will form higher surge because of the winds brought by the t. cyclones push on a larger surface area of the ocean at a longer period of time
T. cyclone traveling w/ high velocity (Storm forward speed) produce high storm surge along an open coast
Lower velocity (Storm forward speed)higher broader storm surge in enclosed bodies of water
Angle of approach to coastWhen a tropical cyclone hits the coast perpendicularly it is more highly form higher storm surge
Coriolis effect-tendency of ocean currents to be deflected because of Earth’s rotation
Northern hemispheresurge largest on the right forward motion (north east quadrant) of the tropical cyclone
Rain fall effectWater level rise quickly in estuaries because large volumes of accumulated rain water from water shed in higher elevation areas are drained by the rivers encounter water driven by the cyclone from the ocean
Bathymetryappearance of ocean or sea bottom resulting to variation in depth
Lower surges w/ higher stronger wavesa shoreline bordered by narrow shelf separated from the open sea by steep slope
Higher surges w/ smaller wavesshoreline bordered by a wide shelf sep. from an open sea by gentle slope
Topographyland configuration resulting from variation in elevation
Geometry of Coastal AreaWide low lying areas with elevation few meters above sea level are vulnerable to surges
Geometry of Coastal AreaThe shape of coastline
Geometry of Coastal AreaStorm surge is higher when tropical cyclone hits a concave coastline
Man made and natural local featuresweakens the storm surge
(1) Mangroves, (2) Coral reefs, (3) On shore vegetation, (4) San dunes(4 EXAMPLES) Man made and natural local features weakens the storm surge
(Nationwide Operational Assessment of Hazards)Project NOAH meaning
(1) PAGASA, (2) Project NOAH, (3) Prediction of potential location of hazards3 Storm Surge Prediction, hazard Map Preparation and Zoning
Construction of Storm Surge BarriersGate like hard engineering structures installed in front of tidal inlets, rivers and estuaries which are closed before extreme water increases
Wet land ProtectionDevelopment of housing, agricultural and industrial areas should be prohibited near coastline
Wet land ProtectionProtection of off shore barrier islands and coral reefs


Question Answer
No alertNo action required
Yellow AlertExpected height: 0.5 to 1 meter
Yellow AlertStorm surge is possible
Yellow AlertStay away from coast or beach.
Yellow AlertPreparations measures must be carried out
Orange AlarmExpected height: 1.1 to 3 meters
Orange AlarmStorm surge is expected
Orange AlarmConditions could become life threatening
Orange AlarmAll marine activities must be cancelled
Orange AlarmFollow evacuation guidelines from local authorities
Red Take ActionExpected height: 3 meters above
Red Take ActionStorm surge is catastrophic
Red Take ActionThere significant threat to life
Red Take ActionMandatory evacuation is enforced


Question Answer
FloodingAbnormal rise of water levels in rivers, coastal areas, plains, and highly urbanized centers
(1) Riverine, (2) Estuarine/Coastal Flooding, (3) Urban Flooding, (4) Catastrophic flooding, (5) Flash floods5 Flood Types
RiverineWhen level of water of a river increases and goes beyond water level
RiverineWater level usually rise slowly in larger rivers with larger catchment area and opposite with smaller ones
RiverineCaused by extreme and sustained rain fall
Estuarine and Coastal FloodingOccurs when seawater encroaches low-lying land that usually still above sea level that can be a result of storm surges
Estuarine and Coastal FloodingCaused by unusually high tides
Urban FloodingOccurs in highly populated areas
Urban FloodingResult of saturation of the ground due to too much rainfall
Urban FloodingResult of presence of large areas of impermeable surfaces like concrete pavements and roof tops
Urban FloodingResult of lack of drainage system
Catastrophic FloodingResult of ground failure or major infrastructure failure
(1) Weakening of soil, (2) Landslides, (3) Liquefaction and subsidence3 Examples of Ground failure
Breakage of dams and levees1 Example of Infrastructure failure
Flash floodsRapid, short lived and violent arrival of large volume of water which can be caused by intense localized rainfall on land that is saturated or unable to absorb water or collapse infrastructure
(1) Topography, (2) River dimensions, (3) Rain fall data, (4) Geology (rocks and soils), (5) GISFlood Risk Assessment Mapping
Diversion canalsConstructed to alleviate flooding
(1) Flood Risk Assessment Mapping, (2) Flood Prediction and Forecasting, (3) Flood Control Engineering Measures, (4) Diversion canals, (5) Artificial Levees or Dikes, (6) Sea WallsMitigation of Flood Hazards

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