Flooding After a Factory Closure
A city neighborhood had a textile factory that closed in 1998. Between 1990 and 2010, the population rose from 18,000 to 22,000. After the closure, a bus terminal opened in 2005 and small shops filled the empty factory building. Since 2015, residents have reported more flooding on Rua das Acácias after heavy rain. The city plans to pave the street and build a concrete wall along the stream. A community group proposes a small park with trees along the stream instead. A council member says: 'The factory closure caused the flooding; paving will solve it.'
1. The council member says the factory closure caused the flooding. Using the timeline, explain why this claim is not well supported. Identify one alternative factor that could better explain more flooding after 2015.
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The timeline does not support the claim. The factory closed in 1998, but increased flooding is reported only since 2015-17 years later. The neighborhood also gained a bus terminal in 2005 and shops in the old factory, and the population grew from 18,000 to 22,000. Those changes can increase paved surfaces and runoff. The closure and the flooding may be correlated in time, but the claim of cause needs evidence linking the closure to drainage changes. A better candidate is urban growth and impermeable surfaces.
2. Compare paving plus a concrete wall with the park and trees. Explain one likely effect of each on rainwater infiltration and runoff, and state one trade-off.
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Paving reduces infiltration and increases runoff; a concrete wall may speed water downstream and protect one street while worsening flooding elsewhere. The park and trees increase infiltration, slow runoff, and can reduce peak flow, but they need space and may not protect quickly in an extreme storm. Trade-off: the wall may give faster local protection, while the park may give broader, longer-term water management and other benefits. The choice depends on whether the priority is immediate protection or reducing the cause.
3. What evidence should the council collect before choosing? Name one source and explain how it would help distinguish the explanations.
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Collect rainfall and flood-level records for at least 10–15 years, plus drainage and land-use maps. Compare flood frequency before and after paving, the bus terminal, and new shops. If flooding rises mainly with impermeable area or with short intense storms, that supports a runoff explanation rather than the factory closure. Soil permeability tests and stream-flow measurements would further show whether water can infiltrate or is being channeled.