KATHMANDU, July 15: It no longer takes a torrential downpour to bring Kathmandu to a standstill. A few hours of steady rainfall is often enough to turn busy intersections into temporary lakes, leaving vehicles stranded, commuters wading through knee-deep water and exposing the capital's chronic drainage crisis.
From Tinkune and Koteshwor to Maitighar Mandala, waterlogging has become an almost inevitable feature of the monsoon. While heavy rainfall intensifies the problem, officials and experts say the root causes lie beneath the roads — in an overstretched drainage network, unchecked urban expansion and rivers that have steadily lost their capacity to carry floodwaters.
According to officials at the Department of Roads (DoR), Kathmandu's drainage system is no longer able to cope even with moderate rainfall.
One major reason, they say, is the widespread and unplanned connection of sewer lines to stormwater drains by local governments, ward offices and the Department of Water Supply and Sewerage Management. "Stormwater drains were designed after studying rainwater flow patterns. But when sewage lines are connected randomly to these drains, their carrying capacity declines, causing rainwater to accumulate on roads," a DoR official said.
A city covered in concrete
Urban planners say Kathmandu Valley's rapid transformation into a concrete landscape has drastically reduced its natural ability to absorb rainwater.
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Open fields, ponds and permeable land that once allowed water to seep underground have largely disappeared, replaced by roads, buildings and paved surfaces. As a result, rainwater now rushes directly onto streets instead of being absorbed into the ground, overwhelming drainage systems within a short time.
The consequences are visible every monsoon, when low-lying areas across the city are inundated after relatively brief spells of rain.
Rivers that can no longer cope
Kathmandu's rivers, once the Valley's natural drainage channels, are also struggling to perform that role.
Experts say the Bagmati, Bishnumati and other tributaries have been narrowed over the years by encroachment and unplanned development, reducing their capacity to carry stormwater during periods of intense rainfall.
The problem has been compounded by the accumulation of sand, gravel and solid waste, which has raised riverbeds and caused water levels to rise much more rapidly than before.
When rivers cannot accommodate the increased flow, excess water spills into nearby roads and settlements, worsening urban flooding.
Shrinking river corridors
In 2012, the High Powered Committee for Integrated Development of Bagmati Civilization and the Bagmati River Basin Improvement Project delineated the flow areas of the Bagmati and its tributaries.
However, experts argue that those boundaries were determined largely by the land left after years of encroachment rather than by scientific hydrological assessments.
Studies show that several stretches of the Bagmati and its tributaries remain significantly narrower than what is required for safe water flow. For example, the river corridor between Sundarijal and the Gokarna Barrage should measure about 35.18 meters in width but is currently only around 20 meters. Similar reductions have been recorded along other sections of the river system.
DoR technicians say the blockage of natural streams and traditional drainage channels has further aggravated the problem, forcing rainwater from surrounding settlements onto major roads.
As a result, areas including Tinkune, Koteshwor Bus Station, Maitighar, Anamnagar, Hanumansthan and Mitrapark continue to experience severe waterlogging almost every time the Valley receives prolonged rainfall.
For many Kathmandu residents, the annual monsoon has become a familiar cycle of flooded streets, traffic paralysis and disrupted daily life. Unless the city restores its natural drainage channels, protects river corridors and modernizes its stormwater infrastructure, experts warn that even ordinary rainfall will continue to trigger extraordinary flooding.
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