In August, images of a devastating flash flood in Nepal shocked the world. More than 6,000 people were killed or remain missing, adding more fuel to the conversation about the preparedness for intensifying flood-related disasters in South Asia. 

Across the region, climate change is "supercharging" extreme rainfall and flooding. Monsoons have always been part of life in South Asia, but their growing intensity is affecting millions of people and claiming an increasing number of lives every year. 

Rapid urbanisation is compounding the risk, fundamentally changing how cities cope with heavy rainfall. Wetlands are disappearing, permeable land is being paved over, and drainage systems are coming under growing pressure. In the process, many cities are losing the very systems that once helped them live with water.

In Bangladesh, nearly 60% of the population is exposed to high flood risk. This year alone, heavy rains and flash floods have killed at least  51 people. In Sylhet, the largest city in north-eastern Bangladesh, the challenge is acute. In 2024, floods affected nearly one million people across the district, exposing the vulnerability of a fast-growing city struggling to manage intense rainfall.

In 2025, we worked with SCC officials to assess the city’s sponginess. The aim was to understand how effectively different parts of Sylhet manage water and where efforts are most needed. The assessment found that nearly 70% of the city has moderate sponginess, 20% has high sponginess, and 10% has low sponginess. But the city-wide figures tell only part of the story.

The results revealed a clear urban divide. Sylhet’s densely built core performed significantly worse, reflecting more hard surfaces and fewer natural water systems. The analysis also points to an important social dimension. Low-income and informal communities can face greater exposure to flooding because of poorer drainage, less resilient housing, and more limited access to services and information. 

Yet 90% of Sylhet retains moderate to high sponginess, creating an opportunity to protect what remains and restore what has been lost.

Before investing in more infrastructure, cities need to better understand where water goes, what prevents it from flowing, and which natural systems are already helping to manage it. Using drone imagery and GIS (Geographic Information System) data, SCC officials mapped the city's chora network, the natural drainage channels that carry water through the city, pinpointing blockages, waste accumulation points, and informal waste dumping hotspots.

Two hotspots were Moin Master Colony and Ahad Miyar Colony, where residents reported that a lack of regular waste collection had led households to dump waste in nearby choras, obstructing water flow, and contributing to waterlogging. 

In response, SCC cleaned the choras, introduced home waste collection, and worked with communities to encourage formal waste disposal. 

In Moin Master Colony, residents described a chora once clogged with waste and marked by foul smells. Today, they say dumping has stopped, water flows more freely and there has been no major waterlogging or overflow this year.

The experience shows what better urban water data can make possible. Rather than treating flooding, drainage and waste as separate problems, cities can identify where they intersect—and target solutions accordingly.

The lesson is clear. Do not wait until flooding becomes an infrastructure emergency to invest in resilience. Protecting the city’s natural drainage corridors can preserve the capacity to manage rainfall, while Sylhet’s choras show that nature-based solutions must work alongside services such as waste management. 

Climate resilience may be the long-term goal, but it is built through the decisions cities make today. So where to begin? At World Water Week, we asked water experts to name one priority for making cities more water-sensitive over the next year. Their answer focused on a need to build awareness and the case for action, from conversations with communities to advocacy for sponge-city approaches in public policy. This involves adapting the message of water-sensitive approaches to the language and needs closest to communities and decision-makers. 

From Nepal to Bangladesh, recent floods have made the stakes increasingly difficult to ignore. For Sylhet, the task now is to turn evidence into momentum: protect the remaining natural systems, test combinations of nature-based and conventional solutions, demonstrate what works, and use the results to make the case for larger investments. The best time to build resilience is before the next flood puts it to the test.