The word disaster implies a sudden overwhelming and unforeseen event. At the household level, a disaster could result in a major illness, death, a substantial economic or social misfortune. At the community level, it could be a flood, a fire, a collapse of buildings in an earthquake, the destruction of livelihoods, an epidemic or displacement through conflict. When occurring at district or provincial level, a large number of people can be affected. Most disasters result in the inability of those affected to cope with outside assistance. At the household level, this could mean dealing with the help from neighbours; at the national level, assistance from organizations such as the International Federation of Red Cross and Red Crescent Societies, the United Nations, various nongovernmental organizations (NGOs) and government agencies themselves. As the limiting factor in disaster response is often the coping capacity of those affected, improving their resilience when responding to disasters is a key approach to lessening the consequence of a disaster.
A vulnerability map gives the precise location of sites where people, the natural environment or property are at risk due to a potentially catastrophic event that could result in death, injury, pollution or other destruction. Such maps are made in conjunction with information about different types of risks. A vulnerability map can show the housing areas that are vulnerable to a chemical spill at a nearly factory. But it just as likely, could delineate the commercial, tourist, and residential zones that would be damaged in case of a 100-year flood or, more devastation, a tsunami.
Vulnerability maps are most often created with the assistance of computer technology called geographic information systems (GIS) and digital land survey equipment designed for use in the field. However, vulnerability maps can also be created manually using background maps such as satellite imagery, property boundaries, road maps, or topographic maps. In such cases the municipality’s planning office should be involved in order to take advantage of the base maps that have already been made for other purposes.
Benefits of vulnerability mapping
Vulnerability mapping can allow for improved communication about risks and what is threatened. It allows for better visual presentations and understanding of the risks and vulnerabilities so that decision -makers can see where resources are needed for protection of these areas. The vulnerability maps will allow them to decide on mitigating measures to prevent or reduce loss of life, injury and environmental consequences before a disaster occurs. An interdisciplinary risk group considers where mitigating measures should be taken before, for example, a flood occurs. Those preparing the maps can overlap flood inundation and slope stability zones with property maps in order to determine which properties and buildings are at risk. They can then notify the landowners and inform them of government subsidies or other support available for undertaking a measure that would protect their homes from potential damage by, for example, water inundation or slope failure.
Vulnerability maps can be of use in all phases of disaster management: Prevention, mitigation, preparedness, operations, relief, recovery and lessons-learned. In the prevention stage planners can use vulnerability maps to avoid high risk zones when developing areas for housing, commercial or industrial use. Technical experts can be alerted about places where the infrastructure can be affected in case of a disaster. Fire departments can plan for rescues before a potentially dangerous event is at hand. During an exercise where a predetermined scenario takes place, the rescue crews may use the map to determine where to respond first to save human lives, the environment or property. They can also be used to evacuation routes to test the effectiveness of these routes for saving large numbers of residents and tourists and moving special groups such as senior citizens, children and those with handicaps. The operations officer can be updated about the disaster situation and the need for and the location of sensitive areas. The vulnerability map can also include evacuation routes to test their effectiveness for saving lives.
After the disaster the vulnerability map and a new map showing the extent of the damage, can assist in assessing how well the emergency was managed. During a post disaster review, the consequences of the disaster can be easily assessed with the help of field data. The evaluators can see if an accurate assessment of vulnerable areas was made and if they were adequately protected. It will also be apparent how effective the mitigation measures were.
Planning the vulnerability map
Collecting information for a vulnerability map
As with any risk management endeavour, a group of experts that are familiar with the risks are an asset for creating a vulnerability map. Working together in an interdisciplinary risk group, will provide comprehensive information about risks and vulnerable sites. The members of the group will increase their knowledge about hazards and the type and extent of disasters that can be expected. Risk groups are most effective when they include an assortment of experts at the municipal level. The group preparing the vulnerability map needs to select those risks that are found in the area to be mapped and decide which risks will be addressed.
Once the risks have been selected, the group then discusses types of scenarios where one of these risks becomes an actual event. The scenarios will describe the date, the day of the week, the time of day, the intensity of the event, the weather conditions, season etc. in order to determine an adequate picture of how the natural or human-caused event will take shape and what will be affected by its impact at the particular time and place that it occurs. A cyclone with a certain speed can hit a particular area with specified impact. A domino-effect scenario can also be written for an event when one of these risks, a natural event or human-caused, can trigger another making the disaster even more devastating. A major flood might be severe enough to encroach upon developed areas. An industrial storage tank containing dangerous goods could be damaged by the rushing waters, causing chemicals to spill into the environment.
Whatever the scenario will be, it needs to be written with enough detailed to provide information about the boundaries of the risk zones. Risk zones should be estimated with the best available knowledge and techniques. With expert help, more accurate risk zones can be calculated for high tides, floods, tsunamis, landslides etc.
The next stage is to determine the objects within the risk zones that will be considered vulnerable and therefore, will be mapped. Vulnerable sites are those where people live, work and visit. They can also be areas where farming, forestry, grazing or industry prevail. Or they can be sites that are difficult to replace or rebuild or which possess historical or cultural values. Habitats with biodiversity or with rare or endemic species preferably require environmental protection. Some sites determined to be high priority for protection, can be classified as such based on the consequences that can incur during or after an unwelcome event.
The baseline data collected for the vulnerability map should be the basis for decisions taken about where prevention and mitigation work needs to be accomplished. Here is an example checklist of objects that could be threatened by a risk. The user can fill in the municipal or regional office that could take responsibility for locating the threatened objects to be mapped.
The office responsible for determining what is vulnerable may vary depending on how the municipal offices are organised. Such offices can be an environmental protection office, technical office, planning office, health care services, education department, culture and recreation department, social services department, agricultural department, forestry department, fire and rescue service department or police station.
Define the area that will be mapped
An important part of the vulnerability map is defining and limiting the area affected by one or more risks. Use the scenarios that the risk group has decided upon to determine the extent of the affected zone. The area to be mapped needs to encompass the entire area where a risk can affect the natural environment to be protected or developed sites whether it be a city infrastructure, houses and apartments, or commercial sites and public facilities. Consider also the resources available to do the field mapping. If resources are not adequate, choose the area where vulnerability is likely to be the highest.
Maps made after a disaster can assist in defining risk areas that were not fully understood or defined prior to the disaster. When mapping the vulnerability to tsunamis, the geographical extent of the initial withdrawal of the sea as well as the maximum horizontal inundation on land, provide valuable lessons learned. Historical information is important for determining the extent of the area to be mapped.
Determine the greatest risks in the area and the potential consequences
The municipal risk group can use a risk and vulnerability table to assure that all risks and threatened objects are identified and classified and that the consequences to life, environment and property are noted. In order to assure that the greatest threats in the area are all mapped, use a table to register the risk group and the objects that are vulnerable.
Consequences can be estimated on a scale of three where 1 = low 2= moderate, and 3 = severe, If a scale of five is used, then 1 = unimportant, 2=limited, 3=serious, 4= very serious and 5= catastrophic. 1= Unimportant temporary slight discomfort, 2= Limited a few injuries, long-lasting discomfort, 3= Serious a few serious injuries, serious discomfort, 4= Very serious several deaths (define how many), several serious injuries and many evacuated (define how many), and 5= Catastrophic several deaths (define how many), thousands of serious injuries and many evacuated (define how many). 1= Unimportant no contamination, localised effects 2= Limited simple contamination, localised effects 3= Serious simple contamination, widespread effects 4= Very serious heavy contamination, localized effects 5= Catastrophic very heavy contamination, widespread effects.
Factors that affect the severity of the consequences are population density, building structures, the duration of the event, whether it was expected or unexpected, and the number and type of incidents that preceded it. Humanmade conditions can also increase the vulnerability of objects such as the way the threatened buildings where made and the construction materials that were used. Consider combustibility and the toxicity when the structure burns. Buildings without proper fire extinguishing equipment mean increased vulnerability. If accident statistics show that a certain type of object is often damaged (for example hotels) as a result of a known hazard (fires), then that object type needs to be specifically marked on the vulnerability map with its own symbol or at least colour. Vulnerability also increases with certain conditions, for example, those in the natural environment such as severity of the weather, topography, and hydrology.
Maps distinguish themselves from sketches or drawings because they have a scale which shows how one unit of measure on the map corresponds to kilometres in the field. Maps also have a directional arrow showing north, and symbols or patterns and a corresponding legend. If analogue maps are the only option, then transparent overlays can be made each plastic transparency with a unique map theme such as hotels or ferry routes.
Although analogue vulnerability maps can be made, there is clearly an advantage to creating the map in a geographic information system (GIS). Several vulnerability maps can easily be made using the same base maps and the same threatened objects but with different risk profiles. Risk zones might look completely different based on the risk type and the actual scenario. In addition the maps can be easily laid upon each other so that any overlapping between risk areas and threatened objects is clearly shown. GIS maps can more easily be updated and printed.
Creating the vulnerability map
Describe what is vulnerable and why
After the risks have been identified, and one or more scenarios have been made and the risk and vulnerability table has been created, the field work can begin. Vulnerability mapping efforts for an environmental disaster begin with an accurate representation of natural features such as rivers, lakes, landforms, topography, and vegetation type.
Man-made features can then be transposed on the natural landscape. The map will then include such information as land use, road and railway systems, power stations, industrial sites, official buildings, business areas, housing areas, schools, and hospitals. Refer to the list of threatened objects presented earlier. Define what is unique about the areas in order to protect biodiversity and cultural integrity for future generations. In addition, any objects that are essential to the emergency operations should be added to the map.
The risk group needs to check with the municipality’s planning office to determine what other maps have been made and which can be useful when creating the vulnerability maps. In some municipalities where a certain risk is very high, specialised risk maps might be available. For example, general flood risk maps on a scale of 1:50 000 or 1:100 000 can give a general overview the risk zone, even if the vulnerability map might be created on a larger scale such as 1:10 000 or 1:5 000. Slope stability maps are generally created in a larger scale such as 1:5 000. They might also be available for the area.
Human-caused risks such as industries, railways, can be pinpointed on a map. When a risk object has been created on the map, the mapmaker assigns the exact coordinates for the object and gives the object an ID-number. Risk objects can be grouped into classes with each class having its own symbol. For large-scale maps, for example, 1:5 000, a symbol which represents the object type can be placed on the building or site. This gives a better overview of vulnerability for those using the map. Objects requiring special protection can also have unique symbols. In order for the map to be complete, risk objects and, where possible, the source of the risk, can also be mapped. If the risk be a natural event such as a cyclone, then the risk is represented as a large area instead of an object.
When creating the vulnerability map, consider the type of information that will be needed in case a disaster occurs so that lives, property and the environment can be saved. In order to use the vulnerability map in a useful way, estimate the area in meters or hectares that would be affected by the specific risk and the number and type of objects within the zone that need protection. Consider transport route and obtain statistics about ferry trips and the number of passengers. Estimate the population that will need to be evacuated. Estimate the total number of villages and if resources allow it, even the total number of houses. If a GIS system with data on the number of inhabitants is not available, then an estimation of population density for areas within any risk zone might be made.
List the environmentally sensitive areas as well as the land uses that are important for the local economy and livelihoods of the residents in the area. If mapping vulnerability to a tsunami, consider what crops are sensitive to salt that is deposited after the tidal wave. Reclaimed fields can grow salt-tolerant crops as a mitigating measure for areas that might frequently be inundated with sea water. Information in the recovery phase of a disaster is useful for improving vulnerability maps by making them more precise. Map the location and extent of the damage that is incurred during the event. Describe and photograph the damage. Show where environmental recovery work was done and describe the work achieved. Hand- held digital equipment can be used for retrieving and recording the data that will be added to a geographic information system if such a system is available.
The vulnerability map is only part of the effort to protect the natural and man-made environment. There also needs to be a willingness on the part of managers and politicians to plan for, finance and complete actions that will reduce the vulnerability of areas and their inhabitants to natural and human-induced hazards. The visual representation that a vulnerability map offers and the discussions that ensue after a presentation can be a major contribution to disaster reduction.