Community early warning systems:
A strategy for the local management of disaster reduction
in Central America
Juan Carlos Villagrán De León, Ph.D., Director, Department of Applied Physics FISICC,
Francisco Marroquín University, Scientific Advisor, National Coordination Office for Disaster
Reduction (CONRED),
Guatemala
In recent years, Central America’s government
agencies in charge of civil defense have started to
engage in a transition from disaster response
approach towards a new concept of risk reduction.
This transition was first made possible by the passing
of laws broadening the mandate of these agencies to
include not just emergency management but also
disaster preparedness and risk migation. However,
this has led to discussions about which would be the
best strategies, institutional coordination and
participation mechanisms, and conceptual models of
risk reduction and management.
A volunteer observes the rain
accumulated in a pluviometer.
One strategy that has been accepted and adopted by several Central American countries to
consolidate this transition is the implementation of early warning systems. The purpose of early
warning systems is to warn the population about a natural phenomenon of such severity that it
might cause death, injury or damage to property, housing, or infrastructure. These systems are a
key component of disaster preparedness, and therefore of risk management.
All early warning systems must satisfy the operational criterion of warning the population
sufficiently ahead of time to let people take at least minimum precautions. They include three
components: monitoring the natural conditions related to the hazard in question, forecasting
events, and warning the population. The operational integration of these components, in the case
of floods, is outlined in fig. 1 below.
Monitoring is carried out in two ways. The more sophisticated approach uses automatic
measuring equipment connected to a telemetric radio communications device. Local conditions
are measured in real time and transmitted automatically to a national observatory in order to be
analyzed at any time. This approach is commonly used in Central America by national
seismology and vulcanology institutes. However, the use of sophisticated equipment requires
highly qualified staff, as well as substantial funds for the acquisition and operation of these
systems.
An alternative and much less complicated approach involves the direct participation of community
members using very simple monitoring equipment. Station operators report the information by
radio to a local forecasting center where the data can be analyzed employing simple routines.
The Central American experience with community
early warning systems has basically focused on flood
warnings. In 1997, I designed and supported the
implementation of a flood forecasting system for the
Coyolate river basin in Guatemala, a project financed
by the Swedish International Development Agency
(SIDA).
In Honduras, similar systems were installed in La
Masica and Arizona with European Union funding and
the coordination of the Organization of American
States (OAS) and COPECO.
In 1999, the RELSAT project, financed by the
European Union and coordinated by the regional
FEMID program, established systems in every
country in Central America that follow the design of
the system that was implemented at the Coyolate
river.
Currently, the demand for implementing community
early warning systems is growing due to the need to
forecast floods locally in many places. CONRED in
Guatemala is implementing this type of system in four
additional basins, and the Costa Rican Risk Prevention and Emergency Management
Commission is preparing a national early warning project to deal with a variety of hazards. At the
regional level, the success of these systems has encouraged the Central American Natural
Disaster Prevention Center (CEPREDENAC) to incorporate the issue as one of the key points of
its Strategic Framework for Vulnerability and Disaster Reduction in Central America.
Fig. 1
Operational scheme for early warning
systems developed to detect floods.
The advantages of using community early warning systems include the following:
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These systems help national civil defense authorities to raise the awareness of rural
communities concerning the need to launch local risk reduction activities.
They establish a radio communications network that allows community members to
exchange social or legal information, in addition to the data on natural hazards.
They have very low operational costs, since the monitoring equipment is very simple and
volunteers operate the system. Recent emergencies such as Hurricane Mitch showed
that volunteers are ready to operate such systems around the clock to reduce the risk of
a natural disaster.
Community early warning systems must be designed
on the basis of the conditions in which they will
typically operate. Factors to bear in mind when
implementing such systems in rural communities
include the following:
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The capacity of the population to operate and
maintain the equipment.
The economic capacity of the community to
acquire spare parts and other items needed
to keep the equipment in operation.
The will of the population to operate the
A member of the local emergency committee directing
an emergency simulation in Guatemala.
system.
In this sense, the equipment may be accepted or rejected based on how complex it is to operate.
With this in mind, a basic infrastructure for community early warning systems for flood mitigation
has been designed to meet the following requirements:
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Low cost and local or regional availability.
Simplicity of use.
Modular integration to facilitate maintenance.
Cost and availability are essential if the system is to be maintained economically by the
community with the technical advice of a national entity. Simplicity ensures that any member of
the community can use the system, a key consideration in the event of an emergency.
Flood forecasting requires a hydrological assessment
of the basin, as well as an analysis of historical data
related to meteorological conditions. The analysis
makes it possible to define which months are more
hazardous, how many floods can be expected on
average each year, and the effect of non-cyclical
phenomena such as hurricanes on coastal areas.
Forecasting center in Zacatecoluca, El Salvador, part of
the RELSAT project. On the wall, to the right, a simple
meteorological station..
The hydrological analysis of the basin helps to
choose the best sites to place sensors, particularly in
terms of their vertical placement, which helps to
determine critical levels that will lead to a flood
downstream. Finally, the integration of
hydrometeorological data and local experience is
valuable in determining how the warning system
should be designed so that it can be operated by
community members.
Typical forecasting procedures begin with the information provided by a simple electronic
meteorological station. The station can forecast rain and takes into account changes in
atmospheric pressure, temperature and wind strength. When risk levels increase, observers in
the higher reaches of the basin are asked to measure rainfall and report the results every hour to
the forecasting center. Once rainfall exceeds a critical level in the space of one to three hours, the
level of the river and its tributaries is measured. Since rainfall is measured consistently, a rise in
the river level helps to confirm the geographic extension and the magnitude of the precipitation.
When the river surpasses its critical flooding level, the forecasting center notifies the local
emergency committee, which issues a public warning and activates its emergency plan.
In the case of floods in coastal areas, where the tides are a key factor, forecasts are based on
data concerning both the expected tide levels and the volume of precipitation. INETER in
Nicaragua and other oceanographic centers publish tide tables for each quarter, or the entire
year, that can easily be checked by date. In the case of ports, the hydrological analysis is limited
to the assessment of sewers and their ability to handle rainwater both at high tide and low tide.
The Local Emergency Committee
As part of the early warning system, one or more local
or community emergency committees must be
appointed to carry out the various activities outlined in
the local emergency plan. These activities include the
following:
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Issuing public warnings.
Carrying out search and rescue operations.
Providing first aid.
Establishing and managing shelters
Coordinating the various institutions involved
in the crisis.
Generally, civil protection institutions establish these
committees and train them for the activities they must
carry out in their communities, including the following:
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Equipment designed by the author to measure river
levels. It includes a sensor with electrodes (the long
tube), an interconnection cable, and an electronic
measuring device. The sensor, placed on the
riverbanks, sends the information to the house of the
operator through a cable. In this way, the operator can
measure and report the river level at any time and in all
kinds of weather without having to leave his or her
home.
Disseminating information throughout the
community about existing hazards and
disaster preparedness and mitigation.
Engaging in risk mapping.
Developing emergency plans.
Defining and properly identifying evacuation routes.
Carrying out drills and simulations.
Conclusions
Community early warning systems are operational structures that enable the population to adopt
measures to minimize the impact of natural disasters. In Central America, these systems are
helping civil protection organizations to move away from the old-fashioned emergency response
paradigm towards local risk reduction and preparedness. Implementing community early warning
systems serves as an alternative to the use of expensive centralized telemetric systems, and
encourage communities to play a much more active role in their own protection.