Strategies to
manage the hazards associated with TROPICAL low pressure systems
(especially tropical cyclones).
"Storm surges cause 90% of
deaths resulting from tropical cyclones and they cause extensive damage
to agricultural land by salt contamination from the inflowing sea water"
When discussing the strategies taken to reduce the
impacts of hazards associated with low-pressure and high pressure
systems, students may present logically sequenced points progressing
from monitoring, prediction and warning of future hazards, immediate
response to lessen the impact once it has occurred to long-term
planning. Students should display a grasp of a number of these, but do
not expect all to be considered as students may choose to use examples
that enable only a limited number of strategies to be discussed.
Management of the tropical cyclone hazard and drought is
covered effectively in Chapter 5 of ‘Hazards and Responses’ by Victoria
Bishop, Collins Educational on which these notes are based. Strategies
available to address the impact of human activity on climate have been
implemented at international level, by government action and by pressure
groups and individuals. Students should re-visit relevant material
covered at AS level.
Management at different tine scales
(perhaps focussed after disaster have occurred in particular
locations)
Short Term - e.g. prediction,
warning, evacuation
Medium Term
- e.g. relief efforts, initial recovery aiming for
normality
Longer Term - e.g. revised management
plans aiming to prevent repetition, rebuilding and improving systems of
prediction and protection, investment to restore / improve normality
Prevent or Modify the Event
(hazard prevention and protection by hazard resistant design)
Modify Vulnerability (by
prediction and warning, by community preparedness (e.g. public
education schemes) and by land-use planning
Modify the Loss (by Aid or by
insurance)
Prevent or Modify the Event
Environmental Control - hurricanes
are powered by the condensation and precipitation process, and it was
hoped that they could be weakened by seeding clouds with dry ice or
silver iodide crystals acting as condensation nuclei. The unpredictable
consequences on global energy transfer and the inconclusive results led
to the research being abandoned.
Hurricanes are predicted to increase in severity and frequency as Global
warming proceeds so management can also be at the the international
scale by concerted government action such as meeting targets for
reducing carbon dioxide emissions.
Hazard Resistant Design - this
focuses on protection against both the storm surge and wind hazards. The
storm surge hazard can be reduced by engineering structures such as sea
walls, breakwaters, flood barriers and levees. Levee failure was a major
cause of the flooding in New Orleans during Hurricane Katrina.
Building design can protect against the storm surge by raising the
building on stilts, and by using concrete or brick rather than wood or
straw which can be more easily swept away. Building design can do
to much to reduce the wind hazard.
Modify Vulnerability
Prediction and warning - coastal
areas at risk of flooding are protected by warning systems. These aim to
monitor tropical cyclone development and forecast their intensity and
tracks so that the population can prepare themselves by moving to
shelters or by evacuating their property and moving away from the danger
area temporarily. (Why is this easier for an
average citizen in Florida, USA than for one in coastal Bangladesh or
one living on a tiny Caribbean island?) The MEDCs are most
protected because of the availability of financial, technological and
communication resources.
One of the most developed warning services is the US government funded
National Hurricane Centre in Miami, Florida. Data from satellites helps
meteorologists look for developing Tropical Easterly Wave circulations.
If a storm develops more detail is collected by reconnaissance flights.
The data is beamed to the NHC for analyse by computer.
Predictions are based on models of atmospheric circulation and tracks of
previous hurricanes. The difficult part of the process is interpreting
the data for warning purposes. If the population at risk are warned and
evacuated then lives may be saved. However, if warnings prove wrong
there are high economic losses from evacuation and therefore lost
production. There is also the impact on the population in terms of their
reaction to future warnings. too many wrong warnings may produce
complacency, and warnings must be issued in a way which will not cause
panic.
A key element is time - as population densities in coastal areas
increase it takes longer for an evacuation to be implemented and exit
roads may be congested. The Lower Florida Keys are 100km from the
closest mainland. Estimates suggest it could take 31 hours to evacuate
the area along the only highway. This is longer than forecasters need to
accurately predict the landfall of an approaching hurricane.
Once the forecast has been made it has to be disseminated to a wider
audience which is harder in an LEDC where many lack radio and TVs - see
Bangladesh case study. also in New Orleans the poorest in society were
less able to respond to the warnings..
Community Preparedness - If warnings
are to be effective, the authorities and public must be aware of the
specific actions to take. Dissemination of information to the public and
evacuation procedures need to be planned in advance. the public needs to
know how to prepare themselves and their property. People may still not
evacuate the area or move to shelters due to personal perceptions,
cultural or economic factors. (Women in Bangladesh
and resistance to storm shelters).
The Pan-Caribbean Disaster Preparedness and Prevention Project
established in 1980 concentrated on technical help, the training of
local people in emergency health care and preparing training materials.
The scheme has had some success regarding the potential loss of life
though the economic losses remain large.
Land-Use Planning - is most effective
in the coastal zone most at risk from storm surges. Past topical cyclone
data and coastal topography can be used to identify areas at high
risk. The aim is to limit development in these areas to uses more
compatible with flooding such as beaches and parkland. This is a
difficult aim to achieve. In LEDCs the need for land, and in MEDCs the
desire for a beach-front location are likely to outweigh the risks
involved, even if people are aware of them. The US Growth Management Act
of 1985 requires local governments to address natural hazards by
limiting public expenditure on developments in high-risk areas,
directing population away from these areas, maintaining or reducing
evacuation times, and having post-disaster redevelopment plans.
Modifying the Loss
Aid - Hurricanes often result in
state and international aid provision in terms of cash and technical
help, for example to restore power supplies.
Insurance - is an important
management strategy especially in MEDCs. The availability of insurance
cover may also encourage people to locate in high-risk areas and the
refusal to offer insurance at a reasonable premium would assist land-use
planning approaches to reducing the risk.
Case Studies:
Bangladesh is one of the world's
poorest nations with GNI PPP per capita income of $US 1440 (2008 Source:
PRB) and it is frequently afflicted by natural disasters. The coastline
is funnel-shaped and vulnerable to cyclones moving over the Bay of
Bengal. About 5 cyclones a year affect the area before and after the
Monsoon season (April - November). The country has to continually deal
with the effects of these disasters on its economy. Money is used for
disaster relief and rebuilding, thus reducing spending on development
projects which would help to raise the general standard of living.
The greatest hazard is the storm surge since
most of the country is low-lying delta and flood-plain. This is densely
populated agricultural land. Most of the coastal land is under 3m and
large numbers of people live on unstable sandbanks called chars in the
delta.
The country has suffered several
disasters. In November 1970 a cyclone produced a 7m storm surge and
winds of 225kph killing 225,000 people and 125,000 livestock. In 1985
10,000 were killed and in 1991 140,000 were killed.
Bangladesh (LEDC) Cyclone management
strategies
Since 1985 management strategies have
concentrated on improved warning systems and building more concrete
storm shelters, rather than hard engineering solutions. However, more
shelters are needed and international aid has helped to fund them. There
were 300 in 1995 and in 2007 the number had reached about 2000.
2008 after Cyclone Sidr the government planned to build 2000 in that
year alone which would give a total of about 4000. An estimated 10,000
are needed. The country has been spending more resources on funding
schemes to prevent river flooding.
'Bangladesh Cyclone' DEC Appeal , Gloria
Hunniford, 1991 What
were the main hazards? What were the main effects? What actions were
planned to react to the problems.
