Storm Hazards

Question 1

The nature of tropical storms

Answer 1

They are huge spinning storms with tropical winds and torrential rain.
They require warm water (27 degrees to a depth of at least 70 metres).
As warm, moist air rises, it releases energy that increases wind speed.

Question 2

Conditions needed for tropical storms to form

Answer 2

A disturbance, such as an area of low pressure that triggers the storm
A convergence of air in the lower atmosphere - either within the inter-tropical convergence zone or along the boundary between warm and cool air masses. This forces warm air to rise.

Question 3

How tropical storms form

Answer 3

They form in the tropics and move westwards due to easterly winds.
They occur at least 5 degrees from the equator.
They cannot form any closer because the coriolos effect isn’t strong enough to make them spin.
They also move away from the equator because of this
They lose strength as they move over land because their supply of warm, moist air is cut off.

Question 4

The Coriolos effect

Answer 4

The rotation of the earth which deflects objects and air (to the right in the northern hemisphere) along the earths surface.

Question 5

Latent heat

Answer 5

The energy that is the driver of tropical storms, while the presence of moisture allows low frictional drag with the surface of the ocean.

Question 6

Circular storms

Answer 6

There is a low pressure point at the centre, called the eye.
In the eye wall there are rising air spirals that cause strong winds.
Near the top of the storm, there is an outflow of moisture - laden air so cloud cover extends for a long distance either side of the eye.

Question 7

Measuring storms

Answer 7

Storm magnitude is measured in the Saffir-Simpson scale.
It measures wind speed from 1 (weakest winds of 120-150kmh) to 5 (strongest winds of over 250kmh)
It also measures damage done from 1 (limited) to 5 (catastrophic)

Question 8

Frequency

Answer 8

Tropical storms are quite frequent with around 100 occurring each year.
Some never reach land so don’t develop into hazards.

Question 9

Predictability

Answer 9

Storms are more frequent in the Northern hemisphere between June and November, and the Southern Hemisphere between November and April.
They can be predicted using satellite imagery to identify cloud formations.
The storm can then be predicted using satellite imagery and models, helping scientists to work out when it will hit.
Predictions are usually accurate however storms are largely irregular due to the number of factors affecting when one will form.

Question 10

Winds

Answer 10

Wind speeds on the ground can reach more than 300km/h.

They can destroy buildings, uproot trees and carry debris long distances before smashing them into other objects.

Question 11

Storm surges

Answer 11

A large rise in sea level caused by high winds pushing water towards the coast, and by the low pressure of the storm.
They account for around 90% of tropical storm deaths.
Waves can reach 10m high if a surge coincides with high tide, devastating coastal communities by destroying buildings, roads and contaminating agricultural land with salt from sea water.

Question 12

Heavy rain

Answer 12

Warm moist air rises, cools, condenses and then falls as torrential rain. This can lead to secondary hazards such as flooding and landslides. During tropical storms, there tends to be around 100mm of rainfall a day.
E.g. Storm Denise 1966, over 1000mm of rain fell in 12 hours
Standing water + warm temperatures = breeding ground for mosquitos, leading to malaria.

Question 13

Flooding

Answer 13

Heavy down pours cause river discharge to increase suddenly, causing rivers to overtop their banks and flood the surrounding area.
Heaving rain and storm surges can also cause flooding in coastal areas.

Question 14

Landslides

Answer 14

Water infiltrates soil and rock, adding weight and making it less stable, increasing the risk of landslides.

Question 15

Social impacts

Answer 15

People may drown, be injured or killed by debris that’s blown around or carried by water.
People left homeless
Electricity cables damaged, so supplies are cut off
Flooding = sewage overflow = contaminated water = disease
Food shortages due to damage to agricultural land

Question 16

Economic impacts

Answer 16

Buildings and infrastructure cost a huge amount to rebuild
Businesses are destroyed, so they can’t trade
Commercial farming suffers as agricultural land is damaged

Question 17

Environmental impacts

Answer 17

Beaches are eroded and coastal habitats are damaged (e.g. Coral reefs)
Fish breeding grounds could be damaged by sediment
Landslides can block water courses so they change course.

Question 18

Political impacts

Answer 18

People may blame authorities for a lack of food, water and energy, leading to political unrest.
Repairs are expensive so the development of the country will be limited.

Question 19

Social impacts - Katrina

Answer 19

1836 people died
300,000 homes destroyed, many homeless and 3 million without electricity
Parts of the 1-10 bridge collapsed, blocking one of the main routes out of New Orleans.
Water supplies were polluted with sewage- 5 died from contaminated water.
18 schools destroyed and 74 badly damaged

Question 20

Economic impacts - Katrina

Answer 20

Largest impact
230,000 jobs lost
Industry disrupted - 30 oil platforms in the Gulf of Mexico were damaged or destroyed, ports such as Gulfport in Mississippi was damaged.
5300km^2 of forest was destroyed in Mississippi, causing around $5 billion lost income from logging
Total cost of damage was around $300 billion

Question 21

Environmental impacts - Katrina

Answer 21

Coastal habitats such as sea turtle breeding beaches were damaged.
Coastal conservation areas such as Breton National Wildlife refuge in Lousiana were destroyed.
Flooding to oil refineries in Louisiana caused spills
Flooding of salt marshes lead to habitat loss
80% of New Orleans was flooded.

Question 22

Economic impacts - cyclone nargis

Answer 22

6000km^2 of agricultural land was damaged, including rice paddies.
40% of food stores were destroyed
Fishing boats were destroyed, meaning millions of people loss their livelihood.
The total cost of damage was around US $4billion

Question 23

Social impacts - Nargis

Answer 23

140,000 people killed
2.5 million left without shelter
450,000 homes destroyed
75% of health facilities destroyed
43% of fresh water ponds, a valuable source of water for local people were damaged by salt water.
70% of people had no access to clean water

Question 24

Environmental impacts - Nargis

Answer 24

380km^2 of mangrove forests were destroyed
Flooding caused erosion and salinisation of the land
14,000km^2 of land was flooded.

Question 25

Hurricane Katrina - Key facts

Answer 25

Hit the south east USA on the 29th of August 2005.
It moved North west and strengthened as it passed over the warm water of the Gulf of Mexico.
It brought winds of around 200kmh and 200-250mm of rainfall to Louisiana, and a storm surge of up to 8.5m to Mississippi

Question 26

Cyclone Nargis - Key facts

Answer 26

It hit Myanmar on the 2nd of May 2008.
It was category 4 as it reached the coast.
It hit with wind speeds of 215kmh and a storm surge of 5m.

Question 27

Prevention

Answer 27

Future development plans can avoid high risk areas.

Question 28

Preparedness

Answer 28

Emergency services can train and prepare for disasters.

Governments can educate people (stockpiling water and food and boarding up windows)

Question 29

Adaptation

Answer 29

Buildings are made up from reinforced concrete or by fixing roofs securely.
They can be built on stilts so that they are above flood water
Flood defences can be built along rivers (levees) and coasts (sea walls)

Question 30

Responses to Katrina - Before

Answer 30

On the 26/08/05 the National Huricane Centre issued a hurricane warning, meaning preparations could begin.
The US coast guard positioned helicopters and boats in high risk areas.
The federal emergency management agency organised teams and supplies.
New Orleans ordered mandatory evacuation - 80% were evacuated before the hurricane reached land.

Question 31

Responses to Katrina - After

Answer 31

The Louisiana superdome in NO sheltered 26,000 people
50,000 were rescued
$5 billion pounds in charity donations was collected.

Question 32

Responses to Nargis - Before

Answer 32

No dedicated cyclone monitoring centre
Indian weather agencies warned Myanmars government 48 hours before the storm hit.
Myanmars weather forecasters issued warnings via TV and radio but didn’t say how severe it was going to be or give any advice on how to prepare.
There was no emergency preparation or evacuation plans.

Question 33

Responses to Nargis - After

Answer 33

The government initially refused to accept foreign aid.
On the 9th of May they decide to accept aid donations such a food and tents.
The UN refugee agency sent shelters, water purification tablets and blankets.
Aid workers weren’t allowed into the country until the 19th of May
Military ruled Myanmar and seized and turned away some aid.