PKU - Peking University
PKU - Peking University
07/29/2026 | Press release | Distributed by Public on 07/28/2026 23:26
Smarter Flood Planning Could Protect Millions as Cities Face Rising Climate Risk
Peking University, Jul 29, 2026: Extreme urban flooding is a growing challenge under climate change, threatening residents, infrastructure, and urban systems. However, traditional emergency planning often relies on static population data and fixed facilities, failing to capture how people move during disasters. A research team led by Professor Zhao Pengjun from Peking University's School of Urban Planning and Design has developed a new approach that integrates human mobility dynamics into flood emergency planning. Their study, titled "Human mobility dynamics for cost-effective flood emergency resource allocation," was published online in Nature Sustainability.
Why it matters
Urban flooding is a complex disaster involving interactions between people, cities, and natural hazards. During extreme events, residents adjust their movements based on flood risks, shelter availability, and surrounding conditions. However, conventional emergency planning often relies on long-term population patterns and overlooks these dynamic changes, leading to mismatches between evacuation needs and available resources.
Key Findings
To address this challenge, the research team developed the PKU-FIM agent-based model, which simulates large-scale population movement during extreme floods through a "perception-decision-action" framework. Using publicly available population, building, and hydrological data, the model reproduces dynamic population distributions at a 1-kilometer scale. The team validated the model using real flood events, including the 2021 Zhengzhou "7.20" extreme flood and Typhoon Mangkhut-related flooding in Shenzhen in 2018. Comparisons with 1.56 billion mobile phone signaling records showed that the model effectively reproduced major human mobility patterns during disasters.
The researchers applied the model to 21 large cities in China with populations exceeding 5 million to evaluate whether emergency shelters could meet dynamic evacuation needs during extreme floods. The results show that approximately 43% of cities experience severe spatial mismatches between evacuation demand and shelter resources under a once-in-a-century flood scenario. In some cities, mismatched areas exceed 2,000 square kilometers, affecting up to 16.76 million people.
Future projections under the SSP5-8.5 high-emission climate scenario show that by 2050, potential flood-affected areas could expand by more than five times. Although population decline may reduce overall evacuation demand, climate change could continue to create significant shelter shortages, leaving approximately 11.75 million people exposed to evacuation risks.
Cost-effective optimization
The research team proposed retrofitting shelters in the top 30% of areas with the largest resource gaps. This strategy achieves a benefit-cost ratio exceeding 28, with an average investment of only $1.39 per person, while significantly reducing disaster-related losses.
Future Implications
The study provides a new framework for climate-resilient urban planning by considering both population distribution and movement during disasters. The PKU-FIM model can help cities identify vulnerable areas, optimize emergency shelter placement, and improve disaster preparedness through targeted, data-driven resource allocation.
*This article is featured in PKU News "Why It Matters" series. More from this series.
Read more: https://www.nature.com/articles/s41893-026-01886-9
Written by: Akaash Babar
Edited by: Chen Shizhuo
Source: PKU News (Chinese)
Why it matters
Urban flooding is a complex disaster involving interactions between people, cities, and natural hazards. During extreme events, residents adjust their movements based on flood risks, shelter availability, and surrounding conditions. However, conventional emergency planning often relies on long-term population patterns and overlooks these dynamic changes, leading to mismatches between evacuation needs and available resources.
Key Findings
To address this challenge, the research team developed the PKU-FIM agent-based model, which simulates large-scale population movement during extreme floods through a "perception-decision-action" framework. Using publicly available population, building, and hydrological data, the model reproduces dynamic population distributions at a 1-kilometer scale. The team validated the model using real flood events, including the 2021 Zhengzhou "7.20" extreme flood and Typhoon Mangkhut-related flooding in Shenzhen in 2018. Comparisons with 1.56 billion mobile phone signaling records showed that the model effectively reproduced major human mobility patterns during disasters.
The researchers applied the model to 21 large cities in China with populations exceeding 5 million to evaluate whether emergency shelters could meet dynamic evacuation needs during extreme floods. The results show that approximately 43% of cities experience severe spatial mismatches between evacuation demand and shelter resources under a once-in-a-century flood scenario. In some cities, mismatched areas exceed 2,000 square kilometers, affecting up to 16.76 million people.
Future projections under the SSP5-8.5 high-emission climate scenario show that by 2050, potential flood-affected areas could expand by more than five times. Although population decline may reduce overall evacuation demand, climate change could continue to create significant shelter shortages, leaving approximately 11.75 million people exposed to evacuation risks.
Cost-effective optimization
The research team proposed retrofitting shelters in the top 30% of areas with the largest resource gaps. This strategy achieves a benefit-cost ratio exceeding 28, with an average investment of only $1.39 per person, while significantly reducing disaster-related losses.
Figure 1. Schematic overview of the developed ABM.
Figure 2. Demand-supply analysis of emergency shelters in China's large cities.
Future Implications
The study provides a new framework for climate-resilient urban planning by considering both population distribution and movement during disasters. The PKU-FIM model can help cities identify vulnerable areas, optimize emergency shelter placement, and improve disaster preparedness through targeted, data-driven resource allocation.
*This article is featured in PKU News "Why It Matters" series. More from this series.
Read more: https://www.nature.com/articles/s41893-026-01886-9
Written by: Akaash Babar
Edited by: Chen Shizhuo
Source: PKU News (Chinese)
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