3.2 - Hazard vulnerability and contrasting impacts

Why people live in hazardous places

A hazard is a potentially damaging process or event. Exposure concerns the people, assets and environments in its path. Vulnerability concerns how susceptible they are to harm and their ability to cope and recover. A powerful event in an uninhabited area can have fewer human impacts than a smaller event affecting fragile homes and essential services.

People may accept risk because a place offers employment, family networks, fertile volcanic soils, tourism or access to fisheries and transport. Some believe protection and warning make the risk manageable. Others lack affordable land, jobs or the money to move. A rare event may be outweighed by daily needs; familiarity with smaller events can also lead people to underestimate an extreme one.

Remaining at risk is therefore not automatically ignorance. Moving can separate a household from work, land, cultural ties and support. Understanding those constraints helps explain why a technically safer relocation site may be rejected or fail.

Physical, social and economic vulnerability

Physical conditions include event magnitude, duration, depth, terrain and secondary hazards. Loose sediment can amplify earthquake shaking; steep slopes can fail; a shallow coastal bay can worsen storm-surge exposure. Location changes what a community must cope with.

Social conditions include housing quality, age, disability, health, education, communication, social networks and trust. A warning in the wrong language or an evacuation route inaccessible to a wheelchair user can leave danger unchanged. Economic conditions include savings, insurance, employment, infrastructure and resources for public services. Losing one boat can be catastrophic for a household even if its monetary value is small nationally.

National development measures provide context but hide inequalities. For example, UNDP's 2025 report using 2023 data records HDI 0.925 for Japan and 0.622 for Nepal. These support the specification's developed/emerging categories, not a claim that every Japanese resident is secure or that Nepal has no capacity. They are also later observations, not the HDIs at the 2011 and 2015 earthquake dates.

Eyjafjallajökull 2010: local and distant impacts

Eyjafjallajökull in southern Iceland erupted beneath glacier ice in April 2010, producing ash and glacier-outburst floods, or jökulhlaups. The Icelandic Met Office's January 2011 account records fast floods containing volcanic debris and ice, with inhabited areas potentially reached quickly. Local impacts therefore included threats to farms, roads and communities as well as ash falling on the landscape.

Ash transported into busy European air routes produced a much wider economic and social impact. A November 2010 USGS account records more than 100,000 scheduled flights grounded during six days. The eruption did not physically destroy distant airports; airborne ash created engine and flight-safety risks, and airspace restrictions interrupted travel and supply chains.