Factors Influencing Vulnerability to Tropical Cyclones

Social Factors: Density, Housing, and Education

A category 5 cyclone hitting an uninhabited island causes zero human disaster. But when it strikes a crowded city, the social characteristics of the population act as an impact multiplier.

• Population Density: High concentration of people in coastal urban areas increases human exposure. When Typhoon Haiyan struck Tacloban City (density of 1,200 people per km²), over 6,000 deaths occurred because residents were tightly packed into a funnel-shaped bay.
• Housing Quality: In Low-Income Countries (LICs) and Newly Emerging Economies (NEEs), millions live in informal settlements built on high-risk marginal land like floodplains. "Kucha" houses made of mud, straw, or corrugated iron cannot withstand wind speeds exceeding 119 km/h. During Typhoon Haiyan, 90% of Tacloban was destroyed because 4.1 million people lived in poorly constructed coastal housing.
• Education and Warnings: Low literacy rates and language barriers can be fatal. In the Philippines, multiple regional dialects meant some communities failed to understand 48-hour "storm surge" warnings, leading to low evacuation rates.
• Demographic Vulnerability: The elderly, children, and people with disabilities have limited mobility. In Hurricane Katrina (2005) and Hurricane Milton (2024), fatalities were concentrated among the elderly and urban poor who lacked private transport to evacuate.

Economic Factors: Wealth and Preparedness

Why does a massive storm in the USA cause fewer deaths than a weaker storm in Bangladesh? Financial resources determine a country's ability to fund infrastructure and execute The 4 Ps (Prediction, Preparation, Protection, and Planning).

• Infrastructure and Hard Engineering: High-Income Countries (HICs) can afford expensive physical defences. The USA spent US$14 billion on levees in New Orleans. In contrast, LICs rely on low-tech community solutions. Bangladesh has built 3,500 cyclone shelters (which double as schools) and uses 45,000 village volunteers with megaphones.
• Forecasting Costs: Predictive technology is expensive. The USA uses 20 dedicated weather satellites. Bangladesh must pay US$12 million annually to access satellite data from other nations.
• The Insurance Gap: In HICs, insured losses allow for rapid private rebuilding (e.g., Hurricane Katrina had US$40–US$55 billion in insured losses). In LICs like the Philippines, US$12 billion in Typhoon Haiyan damages had to be met by government debt and international aid.
• The Vulnerability Paradox: HICs suffer higher absolute economic losses (Katrina cost US$100–US$145 billion), but LICs suffer far higher human costs (Haiyan caused 6,190 deaths and left 4.1 million homeless).

Comparing The 4 Ps in HICs vs LICs

Worked Example: Calculating Cyclone Frequency

Examiners often ask you to interpret data regarding the frequency of natural hazards.

A coastal country records 140 major storm events over a decade. If 98 of these were tropical cyclones, what percentage of the storms were tropical cyclones?

Step 1: Write down the given values.

• Total storms = 140
• Tropical cyclones = 98

Step 2: Set up the percentage calculation.

• $Percentage = \frac{Tropical\ Cyclones}{Total\ Storms} \times 100$

Step 3: Substitute the values and calculate.

• $(98 \div 140) \times 100 = 70\%$

Answer: 70% of the storm events were tropical cyclones.