Cyclone Shelter Siting: Reading a Union Map Against Hazard and Access
A coastal union has three villages: Charpara (population 2,400, 1.5 km from the embankment, road floods at high tide), Middlevillage (population 1,800, 4 km inland on a raised road), and Naptapara (population 900, 0.8 km from the shore behind a low mud embankment). There is one existing cyclone shelter at Middlevillage with capacity 1,200 people. A new shelter can be built at only one site. The union is told to expect a storm surge of 2 to 3 m above normal tide, with landfall possible within 18 hours of a warning. The road to Charpara becomes impassable to buses about 6 hours before landfall, but remains passable on foot and by motorcycle. Naptapara has no raised road. The committee must choose a site and a warning-to-evacuation plan.
1. Compare the three villages for shelter need using distance from hazard, access, and existing capacity. Which village has the strongest case for the new shelter, and why?
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Comparison:
- Naptapara: 900 people, 0.8 km from shore, protected only by a low mud embankment that a 2–3 m surge would likely overtop, and no raised road, so evacuation is slowest and most dangerous. Highest hazard exposure, worst access, no nearby capacity.
- Charpara: 2,400 people, 1.5 km from the embankment, road floods and becomes bus-impassable about 6 hours before landfall but stays usable on foot and by motorcycle. High population, moderate hazard, degrading access.
- Middlevillage: 1,800 people, 4 km inland on a raised road, and already has a 1,200-capacity shelter. Lowest hazard, best access, some existing capacity.
Strongest case: Naptapara. The deciding factors are that it combines the highest physical exposure with the worst evacuation route. A shelter's value is greatest where people cannot outrun the hazard. Charpara is a close second on population, but its people can still reach Middlevillage's shelter on foot or by motorcycle if warned early. Middlevillage is already served and least exposed.
2. The committee proposes building at Middlevillage to enlarge the existing shelter. Evaluate this against the constraints and state the condition under which it would be acceptable.
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Evaluation: building at Middlevillage enlarges capacity where the hazard is lowest and access is best - the place that needs it least. With an 18-hour warning and a surge of 2–3 m, the people at greatest risk are in Naptapara, who have no raised road. Enlarging Middlevillage does nothing for them unless they can travel 4 km inland before the surge, which is unrealistic for 900 people with no raised route, especially the elderly and children.
It would be acceptable only if all of the following held:
- A feasible, tested evacuation route from Naptapara to Middlevillage exists, with transport assigned and time to complete it inside the warning window.
- The enlarged capacity covers the combined at-risk population, not just Middlevillage's own.
- The route stays passable in the worst forecast surge, which the setup suggests it does not.
Since condition 3 fails on the given facts, Middlevillage is the weaker choice. A committee should state the failing condition explicitly rather than reject the option vaguely.
3. Assume the shelter is built at Naptapara with capacity 1,000. Draft the sequence of actions from warning to landfall, naming the decision point at which evacuation must stop.
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Sequence:
- Hour 18 (warning received): activate the committee, alert all three villages by megaphone, mosque announcement and mobile message. Confirm transport for Charpara's elderly and disabled.
- Hours 18–12: move Naptapara residents to the new shelter first, since they have the shortest distance but the worst route; move Charpara's vulnerable groups toward Middlevillage while the road still takes vehicles.
- Hour 12 (decision point): this is the stop-evacuation threshold. After this point, buses to Charpara are unreliable because the road floods about 6 hours before landfall, and people on foot risk being caught by the surge. From hour 12, remaining Charpara residents should be advised to move to the nearest vertical refuge or raised structure rather than attempt the full route.
- Hours 12–6: fill shelters, verify headcounts, secure water, dry food, and lighting; confirm the shelter's own roof and shutters.
- Hour 6 to landfall: lock down, no outdoor movement, shelter-in-place.
The threshold matters because a plan without a stop point invites last-minute movement that kills people. The 12-hour mark is chosen to leave a margin before the road fails at about 6 hours.