Climate Change to Increase Urban Flooding Despite Lower Rainfall
Translated & summarized from NEWSru Israel by baba
A Hebrew University of Jerusalem study warns that climate change will cause more intense, shorter rainstorms, increasing urban flood risks globally despite overall rainfall reduction. Analyzing 32 climate models, researchers found that by the end of the century, 26% of urban areas housing 1.5 billion people could face intensified extreme downpours. Urban development worsens the problem by increasing runoff into overwhelmed drainage systems. The study calls for rebuilding urban flood defenses to cope with these changes.
The story in 5 lines · by baba
- Urban areas worldwide face increased flood risk from intense downpours, despite overall rainfall reduction.
- By 2100, 26% of cities, home to 1.5 billion people, may see reduced rain but intensified extreme storms.
- Storm intensity in the Eastern Mediterranean could increase by 20% in 10-minute intervals.
- Urban development and impervious surfaces worsen flood risks by increasing runoff.
- Researchers call for rebuilding urban flood defenses to address intensified extreme floods.
A new study by researchers at the Hebrew University of Jerusalem indicates that even as global rainfall decreases, cities face a heightened risk of severe flooding due to more intense, shorter downpours. The research, published in the Journal of Hydrology, analyzed 32 global climate models. It projects that under a high-emissions scenario, by the end of the 21st century, 26% of urban areas worldwide, home to approximately 1.5 billion people, will experience reduced overall precipitation alongside intensified extreme rainfall events.
The study combined detailed precipitation modeling with an analysis of urban drainage systems in central Israel, conducting over 5,300 simulations of heavy rainfall. Findings suggest that rising global temperatures will cause storms in the Eastern Mediterranean to become more concentrated in both space and time. While total annual rainfall may decrease, the maximum rainfall intensity over a 10-minute interval is expected to increase by about 20%. Light, drizzly rains will become less frequent, but the most intense downpours will strengthen.
Urban development exacerbates this effect, as surfaces like roads and roofs prevent water absorption, leading to rapid runoff into drainage systems that can be overwhelmed by short, intense storms. The researchers highlight that the increase in impervious surfaces amplifies extreme runoff. "Climate change is fundamentally changing how rain falls," stated co-author Raza Nussbaum. "Our results show that the most extreme floods will intensify. Flood defenses for cities will need to be rebuilt."
Similar trends are anticipated not only in the Mediterranean but also in parts of Africa, southeastern Australia, and the Americas. The scientists emphasize the need to prepare for both arid futures and increased urban flooding.