LocationsThree decades after a sewerage overhaul reshaped the capital, Thimphu is again digging deep and this time to build a climate-resilient drainage system designed to withstand heavier rains, reduce flooding and prepare the city for a hotter, wetter future.
Thimphu upgrades its drainage system as climate risks rise
May 25, 2026
More than 30 kilometres of stormwater drainage in Thimphu city are being made climate resilient through the UNDP and GEF supported project aimed at enhancing resilience of Thimphu and Paro cities.
UNDP/Dechen Wangmo
Three decades ago, Thimphu’s streets were covered beneath clouds of dust. Roads were ripped open. Shops lost customers. Residents navigated trenches and daily inconvenience as the expanding capital was dug up in the early 1990s. Yet beneath that disruption lay the foundation of one of Thimphu’s most consequential urban transformations: the sewerage and drainage network built with support from the Danish International Development Agency (DANIDA).
At the time, many residents saw only disruption and uncertainty. In hindsight, the project arrived just as urbanisation was accelerating and helped equip the capital for decades of growth. Now, about 30 years later, Thimphu is once again under excavation.
From Motithang to Changangkha and through the city core, excavators and construction crews dominate the city landscape. Traffic diversions slow commuters, while shopkeepers and residents cope with mud, noise and temporary loss of access. But officials and engineers say the inconvenience is both necessary and temporary.
What Thimphu is witnessing is not just another round of roadworks. It is part of a broader effort to prepare the capital for intensifying climate risks and the pressures of a growing city.
With the launch of the Primary Drain II works, Thimphu Thromde (municipality) has begun redeveloping the drainage network across the central city area to strengthen flood resilience and improve long-term sustainability. “The works cover drains of different hierarchies in Motithang, Changangkha, and the city core as part of a wider push to build an integrated and resilient storm water drainage system for the capital,” a thromde focal official said.
Lyonpo Chandra Bdr Gurung, Minister for Infrastructure and Transport, Mohammad Younu,UNDP Resident Representative and Ugyen Dorji, Thimphu Mayor duriing a site visit carried out on 12 May 2026
UNDP/Dechen Wangmo
The stormwater drainage redevelopment work is supported through the "Enhancing Climate Resilience of the Urban Landscapes and Communities in Thimphu–Paro Region of Bhutan (ECRUL)" project. With US$20 million from the Global Environment Facility coupled with US$62 million from the Royal Government of Bhutan, the six-year project is being implemented by the Ministry of Infrastructure and Transport in partnership with the UNDP.
On 12 May, the Minister and Secretary of the Ministry of Infrastructure and Transport, the UNDP Resident Representative, and the Thrompon and Executive Secretary of Thimphu Thromde visited project sites, stretching from Sersang School in Motithang to the Kaja Throm area to review progress and discuss implementation challenges.
UNDP/Dechen Wangmo
A drainage system that can withstand the pressures of climate and a growing city for the next 25 years
In recent years, Thimphu has increasingly experienced flash floods, overflowing drains and inundated streets during intense rainfall.
The new stormwater drainage designs draw on historical climate data and align with the Integrated Storm Water Management Plan (2021–2030) and the Thimphu Structure Plan (2023–2047). Engineers have also incorporated records of extreme weather events from the past two decades.
According to Thimphu Thromde engineers, the redesigned drainage system is expected to meet the city’s needs for at least the next 25 years.
Unlike conventional systems designed simply to channel water away, the new infrastructure incorporates climate-resilient, nature-based solutions—including bio-swales, semi-permeable surfaces, and retention ponds—to slow runoff and temporarily store excess storm water during heavy rain.
Thromde officials say retention ponds will help slow water flow and reduce flash flooding downstream. The project also includes cascading ponds for waste filtration and greenery intended to soften the urban heat island effect that often accompanies rapid urban growth.
Some of the most important changes, however, will remain out of sight.
The drains are being built with reinforced rigid concrete structures instead of the traditional random rubble masonry, improving durability and extending their lifespan. Separate underground utility ducts are also being included to keep service lines from clogging drains—a recurring problem in many urban areas.
Officials say the project is about more than infrastructure. They see it as a model for how Bhutan’s cities may need to grow in an era of rising climate risk.
As climate threats intensify, climate-resilient infrastructure is no longer optional but essential to public safety and economic security. For now, Thimphu residents are still living with congestion, muddy roads, and the frustrations that come with construction. But, much like the sewerage works of the 1990s, today’s disruption may eventually be remembered not for the dust it raised, but for the city it helped protect.
****
Related
content
content
