Why Kathmandu keeps flooding

KATHMANDU, July 15: As soon as the monsoon arrives, Kathmandu slips into a familiar crisis. Just a few hours of rain are enough to flood roads in Tinkune, Koteshwor, Maitighar, Teku, Anamnagar, Balaju, Samakhusi, Kalanki, and many other parts of the city. Vehicles stall, shops and ground floors fill with water, and thousands of commuters remain stranded for hours. The usual question is whether the city received unusually heavy rainfall. A more relevant one is why Kathmandu can no longer cope with even ordinary rain.

Blaming rainfall is easy, but global research on urban flooding tells a different story. Rain may trigger flooding, but city planning, land use, drainage systems, and governance determine whether it becomes a disaster. Rain is a natural event. Urban flooding is largely a human made problem.

Most flooding seen in Kathmandu today is not caused by rivers overflowing. It is pluvial flooding, which occurs when rainwater cannot soak into the ground or drain away quickly enough. Roads turn into temporary streams because the city has lost its ability to absorb water.

Kathmandu was once covered with paddy fields, ponds, wetlands, open spaces, and small streams. Together, they acted like a natural sponge, storing rainwater, allowing it to seep underground, and releasing it gradually into rivers. This process reduced flood risks while replenishing groundwater.

That natural system has steadily disappeared in the name of development. Fertile farmland has been replaced by concrete, ponds have been filled, wetlands have been converted into settlements, and open land has given way to buildings and parking lots. Rainwater now lands on asphalt, concrete, and tiles instead of soil. Rather than soaking into the ground, it rushes into drains within minutes, often overwhelming them and flooding streets and homes.

Urban planners describe this as a city that has lost its sponge. A city is not just roads and buildings. It is a living system where soil, vegetation, rivers, wetlands, and people work together. By removing the natural features that absorb water, Kathmandu has also stripped away its resilience.

Many assume larger drains would solve the problem. They would help, but drainage capacity is only one part of the solution. Much of Kathmandu's drainage network was built for a smaller population, less concrete, and different rainfall patterns. Illegal sewer connections, plastic waste, construction debris, and the filling of natural streams have further weakened the system. Water always finds a path. When its natural course is blocked, it creates a new one, often through roads and neighborhoods.

The problem extends beyond drains. Rivers have lost their natural floodplains because of encroachment and unplanned construction. Sand and waste have raised riverbeds, reducing their capacity. When rivers cannot spread into their natural channels, they overflow into surrounding communities. In many places, the city has been built where rivers once flowed. Now, the rivers are reclaiming that space.

Climate change is making matters worse. Rainfall is becoming shorter, heavier, and more intense. Without natural absorption areas, even a few hours of heavy rain can overwhelm the city. Climate change is a factor, but poor urbanization has multiplied the risks.

The crisis also reflects fragmented governance. Different agencies oversee roads, drainage, drinking water, rivers, and urban planning, while Kathmandu, Lalitpur, and Bhaktapur often pursue separate strategies. Water does not recognize municipal boundaries. It follows watersheds and natural terrain, making coordinated planning essential.

Many cities have already adopted this approach. China's Sponge City program restores natural water absorption. Singapore integrates canals with parks and green spaces. Rotterdam uses water squares that store rainwater during storms and serve as public spaces at other times. Copenhagen redesigns streets and parks to channel excess rainwater safely. Their shared principle is simple: cities should make room for water rather than fight it.

Kathmandu must embrace the same thinking. Experts recommend restoring ponds and streams, protecting wetlands, reclaiming river floodplains, separating stormwater from sewage, expanding green spaces, requiring rainwater harvesting in new buildings, promoting groundwater recharge, and creating integrated watershed management across the valley.

Kathmandu's flooding is not just a seasonal problem. It is the result of decades of urban planning that treated concrete as progress while pushing nature aside. The city cannot remove nature's laws. Its future depends on learning to live with water, not against it.