Kathmandu: Much of Kathmandu stands underwater today and the capital’s main river, the Bagmati, is flowing above danger levels after incessant rain lashed much of eastern and central Nepal on Friday and Saturday.
After rainfall exceeding 340mm fell in under three days in many places across the Kathmandu Valley the Bagmati is flowing at 6.16 metres at Khokana: 2.16m above danger levels.
Rivers in eastern and central Nepal are also dangerously engorged: at the time of writing the Narayani River at Devghat is running at 11.5 metres: 2.5m above danger levels. Sunkoshi River in Khurkot also recorded 11.5 m, which is almost 3m higher than the danger threshold.
Rescue-workers have used boats and helicopters to evacuate affected citizens stranded in their homes as water levels rose.
The Government of Nepal states 66 people have been killed since early on Friday, with 60 injured and 69 missing, with floods and landslides closing major roads and disrupting domestic air travel.
“I’ve never before seen flooding on this scale in Kathmandu,” said Arun Bhakta Shrestha, Climate and Environmental Risks Lead at the Hindu Kush Himalayan knowledge centre, International Centre for Integrated Mountain Development (ICIMOD). Kumaltar, in the Kathmandu Valley, received 381.2 and Godavari received 346.6 mm in rains that set in early on Thursday. Large areas of Nepal were projected to see rainfall in the “extremely heavy rainfall” category (over 200mm) on both Friday and Saturday.
A low-pressure system in the Bay of Bengal and the more northerly than usual position of the monsoon trough is the reason for this weekend’s late, and exceptionally intense rain.
Contrary to earlier forecasts which showed another day of heavy rain, ICIMOD’s High-Impact Weather Assessment Toolkit (HIWAT) now shows rain subsiding tomorrow (Sunday).
Scientists say that while climate change is changing the amount and timing of rainfall across Asia, a key reason for the rise in the impact of floods is the built environment, including unplanned construction, especially on floodplains, which leaves insufficient area for water retention and drainage.
They recommend central governments and city planners urgently increase the investment in and planning of both ‘grey’ (engineered) and ‘green’ (nature-based) infrastructure: such as underground stormwater and sewage systems; and the restoration of wetlands or the introduction of permeable pavements and ‘rain gardens’ to increase cities’ capacity to absorb water and help communities adapt.
This unprecedented rain has fallen on soil already saturated following a more than 25% above normal rainfall this monsoon in Kathmandu. Its impact is aggravated by poor drainage due to unplanned settlement/haphazard urbanisation, construction on floodplains, and lack of areas for water retention, and encroachment on the Bagmati river.
Extreme floods from two consecutive heavy monsoon years have caused devastation in many parts of the Hindu Kush Himalaya region in 2023 and 2024, and recent analysis by climate scientists shows Asia’s exposure to extreme rain and flood risk growing by 2030.
The research shows the continent will face the greatest rainfall changes in the world by 2100, with ICIMOD regional member countries Bangladesh, China, and India among 10 Asian countries that have the highest risk of extreme rainfall by the end of the century.
XDI’s 2023 Gross Domestic Climate Risk Dataset, the expert group in physical climate risk, shows that 114 of the top 200 provinces with the highest aggregated damage ratio by 2050 will be in Asia.
Landmark research by Chinese researchers and the UK Met Office published in the journal Science this July showed that climate change is not only resulting in more extreme precipitation, but also greater variability in rainfall – with greater swings between intense rain events. The research used observational data since the 1900s to track already detectable changes – with the greater variability in rainfall posing challenges for weather and climate predictions, as well as for resilience and adaptation by societies and ecosystems.
ICIMOD’s 2023 assessment report, Water, Ice, Society, and Ecosystems in the Hindu Kush Himalaya suggests similar changes in the Hindu Kush Himalaya.
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