The impacts of a tropical cyclone on people and property

Overview

Primary and the secondary impacts of a tropical cyclone, main impacts of a tropical cyclone on people and main impacts of a tropical cyclone on property and infrastructure.

What you need to know

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Questions from this subtopic

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1. 1

   Distinguish between the primary and the secondary impacts of a tropical cyclone.

   Model answer

   Primary impacts are the direct results of the storm's own physical forces as it strikes: buildings unroofed or flattened by wind, people killed or injured by flying debris or drowned in the surge, land and property inundated by seawater and floodwater, and crops and trees destroyed. Secondary impacts follow on afterwards from those primary effects: disease spread by contaminated water, homelessness and displacement, loss of livelihoods and income, food shortages and price rises, disrupted schooling and healthcare, and long-term economic damage. Primary impacts are measured in hours, secondary impacts in months and years.

2. 2

   What damage do the winds of a tropical cyclone do to people and property?

   Model answer

   Sustained winds above 118 kilometres per hour, gusting far higher, strip roofs, blow out windows and collapse walls, and in the strongest storms destroy poorly built housing completely. They uproot trees and bring down power lines and telephone masts, cutting electricity and communications for days or weeks and disabling hospitals and water pumps. Debris carried at speed becomes lethal, causing most wind-related deaths and injuries. Crops such as banana, sugar cane and rice are flattened, and shipping, aircraft and vehicles are damaged or overturned.

3. 3

   Why is the storm surge usually the deadliest part of a tropical cyclone?

   Model answer

   The surge raises the sea by several metres and drives it inland with great force, arriving quickly and often at night with little chance of escape on foot. It drowns people, sweeps away houses, boats and vehicles, and destroys coastal defences, roads and railways. Salt water contaminates farmland, groundwater and reservoirs, so land can be unusable for years and drinking water becomes unsafe. Because the world's tropical coasts are densely settled, and low-lying deltas especially so, the surge reaches enormous numbers of people at once, which is why it has caused the great majority of tropical cyclone deaths historically.

4. 4

   What impacts follow from the rainfall of a tropical cyclone?

   Model answer

   A tropical cyclone can deliver several hundred millimetres of rain in a day, and a slow-moving storm can exceed a metre. Rivers rise rapidly and burst their banks, flooding homes, farmland and towns far inland, sometimes days after the storm has passed and long after the wind has died. Saturated slopes fail as landslides and mudflows, which bury settlements and cut roads, and these are often the biggest killer where the affected land is steep and deforested. Flooding also mixes sewage with drinking water and destroys stored food and seed.

5. 5

   What are the main impacts of a tropical cyclone on people?

   Model answer

   Deaths and injuries occur from drowning, building collapse and flying debris. Large numbers are made homeless and displaced into shelters or camps, sometimes for years, and families are separated. Loss of clean water and sanitation leads to outbreaks of cholera, typhoid and diarrhoeal disease, while standing water breeds mosquitoes and raises malaria and dengue cases. Livelihoods disappear when fishing boats, crops, livestock and workplaces are destroyed, causing loss of income, malnutrition and debt. Bereavement and the loss of home and community leave lasting psychological effects, and schooling is interrupted, which harms children's prospects long after the buildings are repaired.

6. 6

   What are the main impacts of a tropical cyclone on property and infrastructure?

   Model answer

   Housing suffers most, with roofs lost, walls collapsed and informal or timber housing destroyed outright. Roads, bridges, ports and airports are damaged or blocked, which also hampers the relief effort. Electricity, water, sewerage and telecommunications networks fail, and hospitals, schools and public buildings are damaged at the moment they are most needed. Businesses, factories, tourist resorts and fishing fleets are destroyed, and agricultural land is ruined by salt or silt. Repair and replacement absorbs public money for years and diverts it from development.

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