Hurricane theory, fieldwork and Katrina

1) Hurricane Theory

(i) What is a hurricane?

They are low pressure weather systems which have very strong sustained winds over 120km/h are bring torrential rainfall. Cyclones, typhoons and hurricanes are all names for the same weather event.

(ii) How do hurricanes form?

Firstly, for hurricane to develop certain conditions are needed e.g. sea temperatures over 27°, wind speeds need to be constant at ground level and at 12km above ground level and it needs to be in the trade wind belt between latitudes of 5° and 20°.

In low pressure conditions, the air draws in the water vapour from sea. As the air rises, it spirals up. By the time the hurricane gets to land there is air still spiralling upwards. However, the air which has already reached the top has cooled and condensed and this is what causes the torrential rainfall.

Further, for hurricanes to occur wind speed is already relatively medium to high and the upward spirally of unstable warm air causes the wind speed to increase.

(iii) Why do hurricanes form

They form because during spring and summer there is an imbalance between atmospheric heat and the Earth’s heat energy. They form because the sun heats the upper portion of the ocean and a lot of heat energy builds up as a result of it. To remove this amount of heat energy, condensation takes place in the atmosphere.

(iv) Where are hurricanes usually found?

They occur around equatorial countries and are created in oceans in the equatorial region for example; the Gulf of Mexico, the Bay of Bengal and the Indian Ocean.

2. Hurricane fieldwork

(i) How can we measure the magnitude of a hurricane?

They are measured through a Saffir-Simpson scale where the rating of a hurricanes is based on wind speed, storm surge (rise in sea level because of low pressure and strong winds) and damage. See table above.

(ii) How can we predict hurricanes?

Wind speed and temperature across hurrricane forming regions are measured with satellites.On these satellites we can even see the cloud formation and swirling winds. From these meterologists can predict hurricanes. Hurricane Katrina was predicted accurately 6 days before. The official huricane forecasting organisation is the ‘National Hurricane Centre’. (Link: )

3. Hurricane Katrina

(i) What is the location, date and any crucial facts of the hurricane?

Location: New Orleans
Date: 29th August 2005
Rating: Category 5
Wind speed: 175 mph
Rainfall: up to 16 inches in some areas

(ii) What were the causes?

(a)Hurricanes have always occurred and are a way of nature balancing heat.
(b)The city of New Orleans is below sea level; it survives by having levees and flood walls at each side of the city.

(a) Well global warming is causing sea levels to rise which makes it easier for hurricanes to form and reach high intensities is one theoretical cause.
(b) Due to the construction of levees wetlands which were one form of natural defence against hurricanes are disappearing at 25 square miles per year!

Something to think about: should the New Orleans have grown to the size it did in such a perilous location.  Added to that the fact that the levees have not been maintained properly.

(iii)What were the impacts?


(a) 1464 people died.
(b) 80% of the people managed to evacuate but 20% who remained were frightened and traumatised (this 20% consisted of particularly poor people)
(c)Every aspect of life was disrupted; people lost jobs, financial securities, families and health.
(d)Many residents moved to other parts of of the U.S.A – in particular Housten (Texas)
(e) There were many health concerns due to lack of clean water, food and toilet facilities.
(f) 600,000 pets were either killed or stranded in the disaster.


(a)Everyone became unemployed; people lost so much of  their financial stability that the government wasn’t able to collect taxes.
(b)In 2006, it was calculated that the cost of repair and reconstruction was $10.5bn.
(c)Total economic impact was over $150bn.
(d) Oil and gas production was affected hence prices of these resources and joint goods e.g. petrol rose in price too.


(a)There was a significant damage to forestry.
(b) The city incurred severe flooding; it was so bad that by the 31st August 80% of the city was underwater.
(c)Almost all infrastructure was destroyed.
(d)Levees and flood-walls protecting the New Orleans breached.

(iv) How was the hurricane managed: what were the responses?

(a) People were instructed to evacuate.
(b) Within a year levees were repaired.
(c) Temporary floodgates and pumps were put around four main canal entrances to prevent further flooding and damage.
(d) Weirs (low-head dams) were put in place to regulate the flow of the Mississippi River Gulf Outlet (which is a river which comes from the Gulf of Mexico).
(e)Wetlands are being restored as a natural form of protection from future hurricanes.
(f) Improvements are continually being made to preparation plans e.g. more education is given in schools, awareness weeks happen once a year etc.

The lack of a decent local and national government response to evacuating people who could not get out themselves in personal transport which made it seem more like an LEDC disaster

Coast 2050 is a $14bn , 30-year scheme to help protect the area. It includes flood controls, water diversion and coastal restoration. Through this the government will create more marsh land and set up many other defence systems.

(v) Who were the key players involved?

(a) the National Hurricane Centre
(b) Local authority
(c) Central government
(d) Local residents
(e) Emergency services
(f) Engineers

Contending with Extreme Weather

How can we best respond to and cope with the impacts of extreme weather?

Key idea: Adaptation vs. Mitigation 

Extreme weather can bring some very adverse impacts onto area socially, economically and environmentally. So there are ways of dealing with it. We can either adapt to the situation or mitigate. Adaptation is usually used in  these event because these event are either caused by complex human causes such as climate change or natural such as the Milankovitch cycles which are hard to mitigate. Below I have defined each term as it is important to  understand them:

Adaptation: Any change in the structure or functioning of an organism or system that makes it better suited to the environment. For example; Boscastle is a flood prone village thus they have changed the shape of the river so it can hold of more water and cutting the impacts of flooding – not causes.

Mitigation: The process by which you make something less harmful or serious. For example; it is claimed the European heatwave in 2003 was caused by climate change. So people governments have got together like in the Copenhagen  treaty to discuss how we can cut carbon emission to mitigate climate change.

Key concept: Short-term strategies vs. long-term strategies 

Short-term strategies used to contending with difficulties with extreme weather can include increasing the number of medical staff around or evacuating people from a certain area. LEDCs tend to rely ons short-term strategies as they cannot around long-term strategies and they also rely on foreign aid for the short-term strategies.

Long-term strategies tend to be hard engineering and quite costly. The work in reducing the impacts in the long term. So for example to reduce the impact of cars being swept away by floods, Boscastle raised the level of the car park and added extra barriers to it.

How was Hurricane Katrina predicted?

Wind speed and temperature across hurricane forming regions are measured with satellites.On these satellites we can even see the cloud formation and swirling winds. From these meteorologists can predict hurricanes. Hurricane Katrina was predicted accurately 6 days before. The official hurricane forecasting organisation is the ‘National Hurricane Centre’.(Link: )
The hurricane was so violent that people were commanded to evacuate. However, 20% of the population (low income groups) didn’t have their own private transport or due to financial reasons were not able to evacuate and were left stranded in the disaster.

What did strategies did the environmental agency take in Boscastle?

They went for 4 long-term hard engineering strategies to reduce the impacts of flooding. 
  1. The environmental agency made a decision to lay a large relief culvert that would carry excess rainwater. It is twice the size of the old one. 
  2. The River Valency is being widened and lowered from the lower bridge to the car park, so that it has a bigger capacity and can carry more water.
  3. The height of the car park is being raised using stone removed from the river bed. Also barriers are being made for the car park so that if it floods it takes much longer for the cars to be swept away.
  4. There are plans to demolish the lower bridge near the harbour and replace it with a higher bridge further downstream. This will give the river more capacity and help to reduce flooding.

Risk assessment 
Risk assessment is way in which organisations such as the environmental agency can decide whether certain solutions are suitable to the particular hazards.
Boscastle flood risk assessment is done by a method called recurrence interval. It is a graph which displays the probability of floods of different levels occurring. The 2004 flash flood had a 1 in 400 years chance of coming. This does not mean the next one this big will happen after 400 years it could happy after a month and then not happen for 800years. Therefore, it isn’t particularly accurate.

Role of Technology 

As technology advances we are able to predict events faster and more accurately and we are able to find solutions which are more smart and suited to our environments.
So for example in the case of Hurricane Katrina the National Hurricane Centre were able to use new satellites to predicted accurately the hurricane would come in 6 days and help the resident of the New orleans prepare for it.

The met office use technology to forecast weather and throughout time the technology has become more efficient and accurate. For example, the snow we experienced in December 2009 and January 2010 the met office were able to give severe warnings about.

Technology is also used to reduce the impacts if disaster. River Flooding can be a great disaster and in a city like London if there was a big flood so much would be destroyed. With technology engineers were able to create the Thames Barrier which has helped reduce the risk of flooding.

GIS (geographical information systems) is a complex computer system which will show you the geography of an area including demo-graph, physical landscape and buildings in an area. They can be used for flood monitoring because they can monitor flood levels and with the weather forecast; meteorologists can put 2 and 2 together to prepare for a flood.

In extreme heat event like drought technology has been useful here as well because through genetic modification we have been able to create drought resistant crops which means that even in the worst conditions farmers will still have agricultural goods to distribute.

National Oceanic and Atmospheric Administration

NOAA is a similar organisation to the met office and national hurricane centre. They forecast weather, give warning and advice people of coping methods. They use the latest technology and produce some very accurate results. Check their about me section out: