Past vs. modern flood risk: Impacts of rainfall, terrain and urban growth
A false sense of security can be dangerous. The "Safe Development Paradox" is a phenomenon in which flood-control infrastructure makes people feel safe, so communities subconsciously start building closer and closer to historically vulnerable lowlands.
Flood-risk assessment reveals complexities of modern infrastructure and its impact on safety. Researchers at IRIDeS, Tohoku University and Meijo University studied changes in Marumori Town, Japan, comparing historical Meiji-era landscapes with current conditions. They discovered that flood-control infrastructure designed to protect communities may paradoxically worsen flooding during lighter rain events.
While levees effectively reduce flood depths during heavy rainfall, they can trap rainwater, causing inland flooding to increase during lighter rains. This phenomenon, known as the Safe Development Paradox, suggests that the 110% growth in settlement area exposed to flooding may be due to communities feeling overconfident in the safety provided by modern infrastructure.
The study emphasizes the need for a better understanding of the tipping points at which levees shift from mitigating flood depths to worsening them. Despite the effectiveness of levees during extreme storms, such as the 2019 Typhoon Hagibis, researchers warn that they are not foolproof. The findings highlight the importance of considering the interplay between landform modifications, climate change, and urban growth in urban planning to reduce hazard exposure and ensure public safety.
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