Mapping Social Vulnerability to Natural Hazards

Mark Altaweel

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Recently, we have witnessed how natural disasters can take a toll on people’s lives and their ability to make a living. Although some natural hazards like earthquakes are tough to predict, we can still lower the risk by mapping out regions that are at risk and taking precautions before the events occur.

It’s important to note that not every community can manage or recover from these disasters equally. To understand how well a region can bounce back from a major disaster, we need to examine social vulnerability.

Creating a social vulnerability index

The UN-supported Sendai Framework for Disaster Reduction identifies that knowing the locations vulnerable to major natural disasters is a high priority for mitigation and planning for natural disasters.

This is especially true in our world today, where inequality is on the rise, and some regions are at a higher risk for certain disasters while lacking the resources to recover easily. 


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A picture of a town with a tsunami route sign in blue.
Some communities are more vulnerable than others to natural disasters. A tsunami evacuation route sign at an intersection in Nehalem, Oregon. Photo: Nathan J Wood, USGS, public domain.

Recently, researchers have created a high resolution (sub-municipal level) social vulnerability index which can be mapped to regions where natural disasters could occur. This helps to determine not only the potential for a given population to be affected by natural disasters or hazards, but it also allows one to measure the potential impact to that population when disaster does strike.

Mapping social vulnerability in Japan

Researchers collected demographic, economic, medical access, access to emergency shelter, and related data for populations across Japan. Applying principal component analysis and Kaiser criterion allowed select and most impactful variables to be chosen with a Varimax rotation also applied on the data.

The results are then mapped to occurrences of natural hazards, namely earthquakes, tsunamis, storm surges, flooding, and landslides. Using open data, this resulted in the creation of the first detailed map at a country level that shows which regions and areas are most susceptible to natural hazards.

A photo showing a damaged building from a tsunami in Japan.
Damage from the 2011 tsunami in Natori, south of Sendai, in Japan. Photo: Bruce Jaffe, USGS, public domain.

The northern part of Japan, including the Tohoku and Hokkaido regions, were the most socially vulnerable to natural hazards, while rural areas are also generally more vulnerable than urban regions. The results indicate that these regions are least likely to cope and recover on their own from major disasters and would require a lot outside help if disasters did occur.

Using census data to map future social vulnerability during a natural disaster

What the work also demonstrates is that one can create useful social vulnerability maps to help plan for future disasters using open census data so that prior to any disasters occurring disaster relief resources could placed nearby even before disasters strike.

For the long-term, it also means that planners should consider enabling vulnerable regions to better cope for future natural hazards by mitigating socio-economic factors.[1]

The research for Japan shows that we can begin to use census data to better prepare for future disasters and aid.

A similar study was done in Morocco for the Souss basin, which is a region susceptible to flooding. Using similar techniques, mainly principal component analysis on social data, including poverty, ethnicity, gender, disability, education, and age from census information, researchers determined the most impactful variables that show social vulnerability.

That result could then be compared to rainfall and flood data to show which regions are most susceptible to flooding and being less able to recover from flooding events. Similar to the Japan study, rural regions were shown to be the most vulnerable and less able to have needed resources to recover from major flood hazards.[2]

Mapping social vulnerability in the United States

In the United States, the Federal Emergency Management Agency (FEMA) has also created a social vulnerability index at the county level across the United States using research by the University of South Carolina’s Hazards Vulnerability and Resilience Institute.

The scoring system ranges from 0-100, with 100 being the highest exposure to hazards. The data are used to also create a risk index that measures overall vulnerability, with data based on social vulnerability, community resilience, and hazard exposure.

A green choropleth map of the United States showing social vulnerability to natural hazards.
Map of the United States showing FEMA’s index of social vulnerability. Map: FEMA.

The hazard exposure measure includes frequency and historical records of events. Hazards include tornados, floods, earthquakes, wildfires, and other events. Similar to results in Morocco and Japan, rural areas in the United States are the most vulnerable, particularly in Arizona, New Mexico, and South Dakota.[3]

Our exposure to risk and hazards is not equal and some of us are far more vulnerable during our lifetimes to be exposed to natural hazards. Furthermore, our ability to recover from major hazards is not equal, where the region you live in often determines how well your community might recover.

New research is now using multivariate spatial statistics mapped against natural disasters to show regions most at risk. For planners, the results enable better preparation, while also providing  individuals with more information about the communities they live in and how well prepared they are for natural disasters. 

References

[1]    For more on measuring social vulnerability in Japan relative to natural hazards, see:  Raduszynski T and Numada M (2023) Measure and spatial identification of social vulnerability, exposure and risk to natural hazards in Japan using open data. Scientific Reports 13(1): 664. DOI: 10.1038/s41598-023-27831-w.

[2]    For more on the Moroccan study on flooding hazards and social vulnerability, see:  Bouaakkaz B, El Morjani ZEA and Bouchaou L (2023) Social vulnerability assessment to flood hazard in Souss basin, Morocco. Journal of African Earth Sciences 198: 104774. DOI: 10.1016/j.jafrearsci.2022.104774.

[3]    For more on the FEMA social vulnerability map for the United States, see:  https://hazards.fema.gov/nri/social-vulnerability.

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About the author
Mark Altaweel
Mark Altaweel is a Reader in Near Eastern Archaeology at the Institute of Archaeology, University College London, having held previous appointments and joint appointments at the University of Chicago, University of Alaska, and Argonne National Laboratory. Mark has an undergraduate degree in Anthropology and Masters and PhD degrees from the University of Chicago’s Department of Near Eastern Languages and Civilizations.