Natural disasters are sudden unexpected events that cause environmental, financial and human loss. These events include avalanches, blizzards, drought, earthquakes, extreme heat or cold, hurricanes, landslides, tornadoes, volcano eruptions, and wildfires. Their detrimental effects can be thwarted or minimized if the public is sufficiently prepared. GIS offer valuable spatial data to emergency management response units during and following natural disasters. GIS is a valuable tool in addressing natural disaster management processes. GIS can alleviate some of the surprise and fear associated with sudden natural disasters by combining today’s technology with emergency management knowledge.
GIS can alleviate some of the surprise and fear associated with sudden natural disasters by combining today’s technology with emergency management knowledge. Since there are often several agencies or organizations working together during emergencies, using GIS allows trained responders to quickly upload and share information between command centers across town or across the world. When a disaster hits, time means lives. Having access to valuable information instantly is what will provide the basis for future GIS processes.
In the planning stage, GIS can be used to identify future hazards in the event of a natural disaster such as a potential flood zone. Areas that are highly vulnerable during an emergency can be identified through GIS data and proper mitigation proceedings can take place to ensure safety.
Disaster prevention Disaster prevention is the planned reduction of risk to human health and safety. This may involve modifying the causes or consequences of the hazard, the vulnerability of the population or the distribution of the losses. The following activities form part of disaster prevention:
- Hazard assessment: determining the type of hazardous phenomena that may affect the area, their frequency and magnitude, and representing on a map which areas are likely to be affected.
- Vulnerability assessment: assessing the degree of loss that these events will cause to population, buildings, infrastructure, economic activities, etc.
- Risk assessment: quantifying the numbers of lives likely to be lost, the number of persons injured the cost of damage to property and disruption of economic activities caused by the events, and preparation of maps indicating the risk areas.
- Restrictive zoning: implementation of the risk maps in development plans, and development of laws to enforce these plans. Public acquisitions of hazardous areas; alternative land use designation for hazardous areas; removal of unsafe structures; obligatory informing potential buyers of real estate on hazardness of the site; include hazardness in insurance policies of real estate.
- Protective engineering solutions: the construction of engineering works to protect the elements at risk from a potentially disastrous event. For example: dikes, floodwalls, slope stabilization works, erosion control works, cyclone shelters, etc.
- Building codes: the definition of standards for the construction of buildings and infrastructure, so that they are able to withstand a disastrous event of a certain magnitude/intensity. For example: earthquake resistant building codes.
- Informing population: public information and education on hazards and risks in the area. Involvement of communities, schools, offices in disaster management.
Mitigation of natural disasters can be successful only when detailed knowledge is obtained about the expected frequency, character, and magnitude of hazardous events in an area. Many types of information that are needed in natural disaster management have an important spatial component. Spatial data are data with a geographic component, such as maps, aerial photography, satellite imagery, GPS data, rainfall data, borehole data etc. Many of these data will have a different projection and co-ordinate system, and need to be brought to a common map-basis, in order to superimpose them.
We now have access to information gathering and organizing technologies like remote sensing and geographic information systems (GIS), which have proven their usefulness in disaster management.
- First of all, remote sensing and GIS provides a data base from which the evidence left behind by disasters that have occurred before can be interpreted, and combined with other information to arrive at hazard maps, indicating which areas are potentially dangerous. The zonation of hazard must be the basis for any disaster management project and should supply planners and decision-makers with adequate and understandable information. Remote sensing data, such as satellite images and aerial photos allow us to map the variability of terrain properties, such as vegetation, water, and geology, both in space and time. Satellite images give a synoptic overview and provide very useful environmental information, for a wide range of scales, from entire continents to details of a few meters. Secondly, many types of disasters, such as floods, drought, cyclones, volcanic eruptions, etc. will have certain precursors. The satellites can detect the early stages of these events as anomalies in a time series. Images are available at regular short time intervals, and can be used for the prediction of both rapid and slow disasters.
- Then, when a disaster occurs, the speed of information collection from air and space borne platforms and the possibility of information dissemination with a matching swiftness make it possible to monitor the occurrence of the disaster. Many disasters may affect large areas and no other tool than remote sensing would provide a matching spatial coverage. Remote sensing also allows monitoring the event during the time of occurrence while the forces are in full swing. The vantage position of satellites makes it ideal for us to think of, plan for and operationally monitor the event. GIS is used as a tool for the planning of evacuation routes, for the design of centers for emergency operations, and for integration of satellite data with other relevant data in the design of disaster warning systems
- In the disaster relief phase, GIS is extremely useful in combination with Global Positioning Systems (GPS) in search and rescue operations in areas that have been devastated and where it is difficult to orientate. The impact and departure of the disaster event leaves behind an area of immense devastation. Remote sensing can assist in damage assessment and aftermath monitoring, providing a quantitative base for relief operations.
- In the disaster rehabilitation phase GIS is used to organize the damage information and the post –disaster census information, and in the evaluation of sites for reconstruction. Remote sensing is used to map the new situation and update the databases used for the reconstruction of an area, and can help to prevent that such a disaster occurs again.
The volume of data needed for disaster management, particularly in the context of integrated development planning, clearly is too much to be handled by manual methods in a timely and effective way. For example, the post disaster damage reports on buildings in an earthquake stricken city may be thousands. Each one will need to be evaluated separately in order to decide if the building has suffered irreparable damage or not. After that all reports should be combined to derive at a reconstruction zoning within a relatively small period of time. One of the main advantages of the use of the powerful combination techniques of a GIS is the evaluation of several hazard and risk scenarios that can be used in the decision-making about the future development of an area, and the optimum way to protect it from natural disasters.
Remote sensing data derived from satellites are excellent tools in the mapping of the spatial distribution of disaster related data within a relatively short period of time. Many different satellite based systems exist nowadays, with different characteristics related to their spatial-, temporal- and spectral resolution. Remote sensing data should generally be linked or calibrated with other types of data, derived from mapping, measurement networks or sampling points, to derive at parameters, which are useful in the study of disasters. The linkage is done in two ways, either via visual interpretation of the image or via classification. The data required for disaster management is coming from different scientific disciplines, and should be integrated. Data integration is one of the strongest points of GIS. In general the following types of data are required:
- Data on the disastrous phenomena (floods, earthquakes), their location, frequency, magnitude etc.
- Data on the environment in which the disastrous events might take place: topography, geology, geomorphology, soils, hydrology, land use, vegetation etc.
- Data on the elements that might be destroyed if the event takes place: infrastructure, settlements, population, socio-economic data etc.
- Data on the emergency relief resources, such as hospitals, fire brigades, police stations, warehouses etc.
The use of remote sensing and GIS has become an integrated, well-developed and successful tool in disaster management in various countries and regions.
REMOTE SENSING OF ENVIRONMENT