1. What determines the severity of a hazard?

1. Duration:

   1. The length of time that a hazard lasts.

   2. As a general rule the longer the hazard the more severe it is likely to be.

      1. Example: an earthquake that lasts 1 minute is likely more severe than one that lasts two seconds and a drought that lasts ten years is likely more severe than one that lasts three months.

2. Magnitude:

   1. This is the strength of a hazard.

   2. Most hazards are measured on a scale

      1. Example: the Richter scale or the volcanic explosivity index (VEI).

      2. Generally speaking, the stronger the hazard the more severe the hazard is.

3. Predictability:

   1. Some hazards are easier to predict than others.

      1. Example, volcanoes normally give warning signs before they erupt and tropical storms can be tracked from development to landfall.

   2. However, others like earthquakes are much harder to predict.

      1. Generally speaking, hazards that hit with no warning will be more serious.

4. Regularity:

   1. If hazards happen often and in quick succession

      1. Example: an earthquake followed by multiple aftershocks then the severity is likely to be greater.

   2. During hurricane seasons, countries can be hit by repeated storms each causing greater damage because it has not been possible to recover from previous damage.

5. Frequency:

   1. The return interval of hazards of certain sizes.

      1. Example, earthquakes with a magnitude of over 8.0 happen on average once

   2. If the hazard is a less frequent strong event, then it is going to have a bigger impact.

6. Speed of onset:

   1. If the peak of the hazard arrives first or arrives quickly

      1. Example: an earthquake, then the affects are likely to be worse than one that arrives slowly

         1. Example: a drought.

7. Spatial concentration:

   1. Where hazards are located or centred.

      1. Example: earthquakes tend to be focused along plate boundaries, whereas tropical storms tend to be located in coastal areas in the tropics.

   2. Hazards that are located in known areas can be better prepared for and managed better.

8. Areal extent:

   1. If a hazard covers a large area

      1. Example: a drought covering the whole of East Africa, then the severity of the hazard is likely to be more severe, than a flood hitting just one village.

9. The number of hazards:

   1. If multiple hazards hit a location the effects can be more severe.

      1. Example: hazard hotspots like Indonesia can be hit by earthquakes, volcanoes, landslides and flooding all simultaneously.

2. Predicting Earthquakes

1. Scientists can attempt to predict by looking at:

   1. Microearthquakes

   2. Changes in rock stress

   3. Ground subsidence, uplift or tilt

   4. Changes in magnetic field and electrical resistivity of rocks

   5. Animal behavior

   6. Seismic history

3. Factors Affecting the Impact of Earthquakes:

1. Depth: If the hypocentre of an earthquake is close to the surface then it is more likely to cause greater damage than a deep earthquake.

2. Duration: A longer earthquake is likely to cause greater damage than an earthquake that lasts only a few seconds.

3. Magnitude: A stronger earthquake is going to have a greater impact than a weaker one.

4. Time of Day: Time of day can be important. If people are sleeping and get trapped in their beds more people can be killed. In Japan, an earthquake that struck while people were cooking their evening dinner caused widespread secondary hazards (fire) that caused more deaths.

5. Epicentre Location: If the epicentre of an earthquake is an uninhabited region it is going to have a lesser effect than one under a densely populated city.

6. Geology: If an earthquake occurs in solid bedrock it is likely to cause less damage than one centred below an alluvial floodplain which may lead to liquefaction.

7. Economic Development (buildings, planning, preparedness): Generally more developed countries have better zonal planning, building codes and preparedness meaning the effects of the earthquake are less.

4. Hurricanes

1. Hurricanes are normally measured by using the Saffir-Simpson Hurricane Scale developed by the National Oceanic and Atmospheric Administration.

2. Hurricanes are measured on a scale of 1-5 depending on their wind speed and storm surge.

3. Category five storms only sometimes cause the most damage.

   1. The amount of damage caused by hurricanes can depend on several factors including:

      1. Where landfall is (populated or non-populated area)

      2. The development of the country

      3. The warning given to residents and the preparedness of residents.

      4. The existing conditions (saturated ground or not)

5. Drought

1. Studies conducted over the past century have shown that meteorological drought is never the result of a single cause.

   1. It is the result of many causes.

2. Scientists don’t know how to predict drought a month or more in advance for most locations.

   1. Predicting drought depends on the ability to forecast two fundamental meteorological surface parameters, precipitation and temperature.

   2. From the historical record, we know that climate is inherently variable.

   3. We also know that anomalies of precipitation and temperature may last from several months to several decades.

   4. How long they last depends on air–sea interactions, soil moisture and land surface processes, topography, internal dynamics, and the accumulated influence of dynamically unstable synoptic weather systems at the global scale.

3. Meteorologists have made significant advances in understanding the climate system.

   1. It may now be possible to predict certain climatic conditions associated with ENSO (El Nino) events more than a year in advance.

   2. For those regions whose climate is greatly influenced by ENSO events meteorological forecasts can reduce risks in those economic sectors (mainly agriculture) most sensitive to climate variability and, particularly, extreme events such as drought.

4. Droughts endanger lives and livelihoods through thirst, hunger (due to crops dying from lack of water) and the spread of disease.

5. Millions of people died in the 20th century due to severe drought and famines.

   1. One of the worst hit areas was the Sahel region of Africa, which covers parts of Eritrea, Ethiopia and the Sudan.

6. Droughts and famines can have other geographical impacts.

   1. If drought forces people to migrate to a new home it could put pressure on resources in neighbouring countries.

7. Droughts can have a severe impact on MEDCs as well as LEDCs.

   1. Droughts have caused deaths in Europe in recent years - especially among the elderly.

   2. In the UK in the summer of 2006, there were hose-pipe bans and campaigns to make people save water.

6. What factors influence our risk perception?

1. Is the risk voluntary? Professional soldiers for example will perceive the risk of being shot differently from a civilian.

2. Time scale: people perceive immediate impacts of a hazard as more severe and 'real' than long-term ones. In an earthquake for example the risk of a building falling on you is more feared than the long-term risk to your health.

3. Psychological perception: certain hazards create a very intense fear response in humans for example the fear of fire and any hazard that might cause this will be perceived as worse than an avalanche.

4. Understanding/Knowledge: We fear what we do not know much about or we fear it less due to a limited understanding of the true risk.

5. Media: Certain hazards are widely publicised and covered in the international media. This can colour our perception of risk.

6. For a disaster to be entered into the database of the UN's ISDR (International Strategy for Disaster Reduction), at least one of the following criteria must be met:

   1. A report of 10 or more people killed

   2. A report of 100 people affected

   3. A declaration of a state of emergency by the relevant government

   4. A request by the national government for international assistance

7. Methods available to dealing with hazards:

1. Preparation:

   1. Governments might consider how they can educate and prepare their populations for a disaster so that they know what to do in a hazardous event.

      1. Also, governments can put into place laws and building codes to govern what can be built and to what standard, so that hazard impacts from hurricanes, earthquakes etc can be reduced.

2. Prediction:

   1. This is the mechanism by which we try to forecast when and where a hazard will occur.

      1. There are a huge range of prediction methods now for a huge range of hazards, think about the Avalanche risk charts you may have seen whilst skiing.

      2. We can use satellites, river flow meters, sulphur dioxide meters, tilt meters etc to predict different hazards.

      3. We are better at predicting some hazards such as flooding, than we are others, such as earthquakes, because some of the warning signs are clearer and because of the amount of response time to each hazard.

3. Prevention:

   1. These are the methods that we can put into place as human beings to either prevent the hazard entirely or prevent some of the negative impacts of a hazard.

      1. Some hazards such as forest fires can be prevented, by using fire breaks and prescribed (deliberate fires) major forest fires can be stopped.

      2. Other hazards cannot be prevented, such as Hurricanes.

      3. However, we can prevent some of the flooding during hurricanes by having correct drainage systems and coastal defences.

8. Reducing Vulnerability - Preparation

1. Aid:

   1. Aid can be used as an adjustment before potential hazards strike or after hazards strike.

   2. Aid before hazards strike will take the form of development aid and may include:

      1. The building of wells to reduce drought and disease

      2. The improvement of irrigation and the introduction of GM crops to reduce famine

      3. The building of dams to reduce the risk of flooding and droughts

      4. The building of roads and mobile networks to improve transport and communication throughout a country

      5. The building of schools to improve education about hazards

      6. The building of hospitals to reduce hazards like disease and treat people injured in hazards

   3. Aid given after a hazard or during a hazard is more emergency aid. Emergency aid may include:

      1. The sending of rescue teams to search for victims

      2. The provision of medicine or doctors to help injured

      3. The provision of food and clean water

      4. The provision of tents and blankets, etc.

   4. Aid may also be given later to help rebuild after a disaster

      1. Example: rebuilding homes, roads, schools, hospitals and electricity supply.

2. Insurance:

   1. Insurance is the act of insuring (protecting) property, people, businesses, etc. against the risk of something happening.

      1. Example: a person dying or being injured, or property being flooded or burnt down

   2. To insure something it is necessary to pay a premium appropriate to the likelihood of something happening

      1. Example: an 80-year-old person is likely to die fairly soon, so any premium will be high, but the likelihood of a 25-year-old dying shortly is much less so the insurance premium will be much less

   3. Normally insurance policies are taken out with private companies, but if the risk of insuring is too high, then private companies may refuse insurance.

      1. In these circumstances, governments will sometimes offer insurance.

   4. Hazard Mapping (Land use planning or zoning)

      1. Hazard maps are created by calculating the vulnerability of different areas to natural hazards.

      2. Hazard maps are often made to calculate populations’ vulnerability to hazards like earthquakes, hurricanes, volcanoes and floods.

      3. Once potential hazards are known then appropriate adjustments can be taken.

      4. Adjustments may include:

         1. Creating zones where building is not permitted because it is too dangerous

         2. Creating zones where only low-value uses are permitted

            1. Example: farming

         3. Protecting areas that are vulnerable to hazards with the use of defences

         4. Evacuating vulnerable areas (and possibly allowing managed retreat in coastal areas)

         5. Rebuilding vulnerable areas to new building standards

      5. When creating a hazard map several variables will be considered.

         1. Example: scientists creating an earthquake hazard map will look at the following:

      6. Proximity to plate boundary or known fault

      7. Seismic history (frequency and magnitude)

      8. Geology (bedrock is much more stable than alluvial deposits which are vulnerable to liquefaction)

      9. Gradient (flatter ground is generally more stable than steep land)

      10. Possible secondary hazards (proximity to the coast for things like tsunamis, but also hills for landslides (forested/deforested))

9. Responses to a Hazard:

1. Short-term response:

   1. A response in the days and weeks immediately after a disaster.

   2. Short-term responses mainly involve search and rescue and helping the injured.

2. Mid-term response:

   1. Responses in the weeks and months following a disaster.

   2. Mid-term responses involve re-opening transport links and getting electricity and water supplies operational again.

   3. It might also involve establishing longer-term refugee camps where there has been large-scale destruction.

3. Long-term response:

   1. Responses that go on for months and years after a disaster.

   2. It involves rebuilding destroyed houses, schools, hospitals, etc.

   3. It also involves kick-starting the local economy.