Strategy for Disaster Reduction
Latin America and the Caribbean
Newsletter ISDR Inform - Latin America and the Caribbean
early warning systems:
In recent years, Central Americas 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.
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.
The advantages of using community early warning systems include the following:
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:
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:
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.
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:
Generally, civil protection institutions establish these committees and train them for the activities they must carry out in their communities, including the following:
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.
For more information,