From deep in the Himalayas to the rough, hilly terrain of central Texas, regions around the world have seen a raft of flash floods this past week that have left death and destruction in their wake.
Flash floods in Nepal’s Rasuagadi—located 120 kilometers north of capital city Kathmandu—swept away a key bridge over Bhotekoshi river that separates China and Nepal, on Tuesday morning, while killing eight and sweeping away 19 others.
The flash floods started upstream on the Bhotekoshi river in China earlier, on July 8.
According to China Daily and Xinhua, China’s north and west regions experienced flash floods and landslides last week as annual ‘Plum Rains’ left a trail of destruction and prompted the mobilisation of rescue workers to pull people from floodwaters with red alerts issued for the region.
Unfortunately, officials at Nepal's Flood Forecasting Division under the Department of Hydrology and Meteorology didn’t see the flood coming in the Bhotekoshi river until 6 am on the morning of July 8. As reported by The Kathmandu Post, Trishuli river basin underwent devastation due to this lack of cross-border communication mechanism for climate events. The Flood Forecasting Division came to know about the flood only after it reached Betrawati,the border between Rasuwa and Nuwakot districts.
Till July 9, the floods in Nepal have claimed at least 8 lives, while 19 have reportedly been missing (11 Nepali nationals, including two police and six Chinese nationals) in the flood, Nepal Police told The Kathmandu Post.
Halfway around the world, on July 4, flash floods inundated large parts of central Texas to claim at least 110 lives, while more than 160 people went missing after the devastating floods, according to NBC News.
Closer home in India, Himachal Pradesh, too, has been reeling under the wrath of endless heavy rainfall and cloudbursts that has caused about 85 deaths so far since June 20. 54 people have lost their lives due to rain-related disasters like cloudbursts, flash floods and drowning incidents, according to ANI. The state has also witnessed consequent damage to life, property, livestock and infrastructure.
The disaster, though separated by time and space, points to a few common underlying factors that include extreme and erratic rainfall patterns, unique geographical features, and the devastating effects of climate change on vulnerable regions. From Texas to Nepal, a lack of proper weather monitoring and information sharing systems indicate the heightened need for robust preparation from the government apart from highlighting the critical need for early warning systems.
Considering the devastative floods in Texas, climate change has once again become the centre of conversations. According to ClimaMeter, the extreme weather conditions preceding the floods, delivering more than double the typical monthly rainfall in just one day, indicated a cause beyond natural climate fluctuations.
Located in one of the world’s most vulnerable regions to climate crisis, Nepal had witnessed extreme weather events over the past decade and a half. However, experts say that extreme weather events such as dry spells, droughts, below average precipitation, heavy rainfall in a short period, rains beyond the monsoon season, above-normal winter temperatures, have become more frequent in the country.
The Himalayan region, where Himachal Pradesh also lies, is particularly vulnerable because of its complex topography. According to a 2021 study published by the University of Leeds, Himalayan glaciers are melting rapidly—losing up to 40% of their area, and shrinking from a peak of 28,000 km2 to around 19,600 km2 in 2021.
The immense destruction caused by these events emphasises the need to understand the underlying factors behind their increasing frequency and severity.
What are Flash Floods?
According to US National Weather Service, a flash flood is caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours. Flash floods are usually characterised by violent torrents followed by heavy rains that rip through river beds, urban streets or mountain canyons.
They are expected to occur within minutes or a few hours of excessive rainfall. They can also occur even if no rain has fallen for instance after a levee breaks or a dam has failed, or after a sudden release of water by a debris or ice jam.
Contributing Factors
Extreme rainfall and severe flooding caused due to climate change pose challenges for policymakers as they threaten to overwhelm flood defences.
According to Down to Earth, this year’s monsoon rains have caused deadly damage on the Indian side of Himalayas, with Himachal Pradesh witnessing the worst impacts over the past few weeks.
Scientists have long attributed soaring temperatures as the cause of more extreme events such as torrential rainfall and floods across the world, including Texas Hill Country.
According to The World Meteorological Organization, warmer air can hold more water vapour—for every one degree Celsius rise in average temperature, the atmosphere can hold about 7% more moisture. This makes storms more likely to produce higher intensity, frequent and long-lasting precipitation, which eventually causes severe flooding.
According to The Indian Express, the Texas flash floods likely unleashed due to a warmer than usual water of the Gulf of Mexico that could have contributed to extreme rainfall. Higher sea surface temperatures lead to more evaporation and moisture transport to the atmosphere, which ultimately results in an increase in rainfall.
Meanwhile, the flash flood in Nepal’s Bhotekoshi River along its border with China is attributed to heavy rainfall on the Chinese side and extensive damaged infrastructure in the Timure area on the Nepali side. According to Mint, the cause of the flash flood is still under investigation. However, the heavy rainfall in the Tibetan region may have triggered the surge but the exact reason has not yet been confirmed. The News Himachal too underscored that experts attribute Himachal Pradesh’s increasing instances of such events to both climate change and unregulated construction in ecologically fragile zones, resulting in more intense, unmanageable cloudbursts and other extreme weather events.
According to a study published in the journal Nature, flooding causes devastating impacts worldwide. The report states that global damages from such natural disasters amounted to an estimated $651 billion and affected 1.6 billion people between 2000 and 2019 alone. The report indicated that the losses from these events could increase by a factor of 20 by the end of the 21st century.
Understanding and mitigating future natural hazards is a critical imperative given the erratic nature of weather patterns due to climate change.
