Tropical Hazards Flashcards
What are storm surges?
A rapid rise in sea level in which water is piled up against the coastline. Caused when wind driven waves pile up water against a coastline combined with the ocean heaving upwards as a result of much lower air pressure
What are the conditions needed for a hurricane?
Sea temperatures above 27 degrees Celsius (maintains rising air currents)
Ocean depth of at least 70m (moisture provides latent heat)
At least 5 degrees north or south of the equator
Low level of air convergence in the lower atmospheric circulation system
Rapid outflow of air in the upper atmospheric circulation
Where do hurricanes happen?
Between 5 and 20 degrees north and south such as; Caribbean sea West of central America Arabian sea Southeast Asia Madagascar North Australia
How are hurricanes measured?
Saffir-Simpson scale, a five point scale based on central pressure, wind speed, storm surge and damage potential
What do the impacts of hurricanes depend on?
Intensity of the storm Speed of movement Distance from the sea Physical geography of the coastal area The preparations made by a community Warnings and community response
What are the major impacts of a hurricane?
Winds
Heavy rainfall
Storm surges
Why are winds a major impact of a hurricane?
Can exceed 150km/h
Can cause structural damage to buildings and bring down electricity transmission lines
Huge amounts of debris are flung around
Why are heavy rainfalls a major impact of a hurricane?
Can exceed 200-300mm = flooding, landslides and mudslides
Why are storm surges a major impact of a hurricane?
Flooding can extend inland - main cause of deaths in hurricanes
Agricultural areas suffer for long amounts of time due to saline contamination
How can we predict a hurricane?
Weather bureaux such as National Hurricane Centre in Florida use satellites to track tropical storms
Comparing computer models with information to give a predicted path (although this is difficult as storms can be unpredictable)
Difficult to do in poorer countries, but some have established warnings - e.g. 1997 Bangladesh, Cox Bazaar area allowed for the evacuation of over 300,000 people so deaths were kept under 100
How can we prevent a hurricane?
Cannot be prevented
Research into cloud seeding to cause more precipitation so that the cyclone releases more water over the sea - weakens the system when approaching land (but this effects the global energy system so research has been discontinued)
How can we protect against a hurricane?
Predicting the landfall enables evacuation and full alert of emergency services
People can strengthen homes to withstand high winds, retrofitting and stilts
Hurricane drills can be practised. For example; Project Safeside in Florida is a hurricane awareness programme for drills for schools and Emergency Operations centre of the state
Land-use planning
Sea walls, breakwaters and flood barriers
How can people prepare for a hurricane?
Communities can mitigate
e.g. Outer Banks Mitigation plan (near North Carolina) aims to save lives, money, properties and natural resources - reducing future vulnerability and speeding up recovery, places importance on giving the public as much information as possible
What caused Hurricane Katrina 2005?
Category 5
Windspeeds of 280km/h
Central pressure of 902mb
Very fatalist approach, knew it was going to happen 12 months prior, affects were mainly the fault of being unprepared. (150,000 remained by choice)
What were the risks and vulnerabilities of Hurricane Katrina 2005?
New Orleans lies on the Gulf coast which is very susceptible to hurricanes
Original flood control measures had resulted in the shrinkage of soils which meant that 50% of land was below sea level
Levee system was not constructed to modern standards and the replacement work was only 60%-90%
Only told 19 hours beforehand to evacuate
