Across Nepal, thousands will be skipping this year's Dashain festivities in honour of loved ones lost after floods and landslides devastated the country and took over more than 200 lives.
With Nepal receiving 80% of its annual precipitation during the monsoon season, the country's citizens are no strangers to rainfall-driven disasters.
But even before last week's exceptional rain, it was clear that 2024 was a particularly heavy monsoon, with rainfall records broken across the Hindu Kush Himalayan region.
Nepal's Department of Hydrology and Meteorology confirmed that 2024's monsoon had registered 25% above normal rainfall, with the rain that fell on 27th and 28th September pushing that figure to 32% above.
Such rainfall is likely part of a wider change in rainfall patterns: and of a monsoon that we can be confident will hit our region with ever greater force and intensity in the years to come.
While the impacts of last month's rain were not limited to cities, Kathmandu Valley was an epicentre: receiving a record-breaking one fifth of the total annual average rain of Nepal in the space of just two days, recording the highest number of deaths.
The floods were a stark reminder that, given the high population sizes involved, it's particularly urgent that city-planners, disaster risk reduction officials and practitioners, and development officials take urgent steps to both protect their populations, and adapt.
A CLIMATE INJUSTICE
The scientific links between a warming planet and more frequent and more intense rainfall events are well evidenced. While Nepal's share of global emissions from the burning of fossil fuels is 0.1%, the country is the fourth most climate-vulnerable in the world.
As we move towards the annual UN global climate change talks, which open next month (Nov 11) in Azerbaijan, ICIMOD will be supporting negotiators from Nepal, and the other countries of the Hindu Kush Himalaya region, to push for the fastest possible phase-out of planet-warming fossil fuel energy.
We'll also continue to argue for those in this region to be prioritised for urgent adaption investment as well as helping demonstrate where compensation under the new global 'Loss and Damage' fund is truly justified.
But we know too that thanks to the length of time greenhouse gases remain in the atmosphere, even if we cut our ties with dirty fossil energy tomorrow, Asia's exposure to rain and flood risk is set to continue to grow in the very near-term. According to the International Finance Corporation, in Nepal alone, over a third of a million people could be affected by river floods from climate change each year by 2030.
With the percentage of people worldwide who live in urban areas expected to increase by 68% by 2050 (Manandhar et al., 2023), cities cannot afford to stand by and wait for emissions cuts. Planners, officials and development partners have a moral imperative to act fast and lead on both effective planning and expansion together with adaptation.
CITIES MUST CHANGE COURSE
Current practices are in fact having the reverse effect. So-called 'pluvial floods' occur when heavy rains overwhelm drainage systems and natural waterways. To mitigate risks of rain and river flooding, city planners in South Asia have long prioritized grey infrastructure such as stormwater drainage systems.
It is now clear that, while well intended, in the teeth of such fast-increasing rain events, these approaches are having the reverse effect and are in some cases actually exacerbating urban floods.
This is particularly the case when combined with other development practices: especially poor solid waste management which clog drainage systems; the increase in impervious pavement that prevents rainwater from infiltrating into the soil, and obstruct flows in waterways; and floodplain encroachment, including unplanned settlements, which encase land, particularly along the banks of major rivers, in concrete, or other impermeable material, in our rapidly urbanizing cities. Poverty is an important feature of this encroachment: with the poorest and most marginalized often settling in the poorest, most hazard-prone land such as that on riverbanks. Solutions to this are not cheap but must be found.
With flash floods causing 220,000 deaths and $1trillion in damages worldwide since 1980, there has been a global scramble for ways to transform cities' capacity to absorb and manage stormwater.
The good news is that not only does this mean that viable solutions to pluvial floods exist, many of these are sustainable, low-cost, and bring other co-benefits to nature and human health.
Most of the best solutions are found in, or mimic, nature: with rain gardens, green roofs, recharge ponds, wetland diversity including marshes and permeable pavements all shown to reduce the impact of heavy rainfall by increasing water infiltration.
Many such "green infrastructure" approaches are already being deployed in other cities across South Asia, in combination with other locally appropriate "grey infrastructure" investments, where they hold the potential to alleviate urban flooding and resolve a host of other urban issues, including municipal solid waste management, spatial planning and risk zonation.
Hyderabad has introduced 'rain gardens', landscapes that are purposefully built in a shallow area of ground or dip which receives water run-off from impervious areas like roofs, paths, carparks and compacted lawns, and planted with plants that can stand waterlogging for up to 48 hours at a time.
Urban green and open spaces have been shown to have tremendous absorptive capacity: soaking up to 50% of rain after one hour of precipitation.
Large detention ponds are also extremely effective at holding water during storm events: while flood embankments along the right bank of the Jamuna River are providing protection at Sirajganj in Bangladesh.
A blended flood mitigation approach, of low-impact development, which mimics natural processes to allow water infiltration, protect water quality and aquatic habitat, and rainwater harvesting, in an urbanised area of Chattogram in Bangladesh has cut flood extent by over a quarter.
China, meanwhile, has led the field with its 'sponge city' initiative: rolling out new canals and ponds and restoring wetlands – easing waterlogging and improving the urban environment.
For a city such as Kathmandu to get on the front foot with a rapidly changing climate, we need the political will, bold regulation and enforcement, and faster flows of finance to deploy and scale such approaches up.
With a flagship programme in Zhengzhou designed to soak up 200mm of rain per day overwhelmed when the city saw that much rainfall in just one hour in 2021 (many places in Kathmandu received over 250mm of rain on 28th September), it's clear that even the most proactive mitigation measures have limits.
So while we set about this urgent work of transforming our cities, it remains equally vital for all of us to push with ever more vigour for faster emissions cuts, especially among G20 economies, to ensure those of us in the global south that have contributed the least to causing such extreme rain events can keep our heads above water.
Prasesh Pote Shrestha is a Civil and Environmental Engineer and Research Associate in Sustainable Mountain Settlements at the International Centre for Integrated Mountain Development. The views expressed are his own.
