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The remains of Sarpang town in the aftermath of monsoon floods in 2016 (Photo: Kuensel)
The remains of Sarpang town in the aftermath of monsoon floods in 2016 (Photo: Kuensel)

Flash floods: Bhutan’s biggest dilemma

As Bhutan braces for yet another torrential monsoon, Gopilal Acharya, explores the threats of water-induced disasters to the country

 In the evening of June 26 last week, Bhutan got its first warning sign of a potentially stormy summer once again. A couple of flash floods in the east of the country damaged public infrastructure and destroyed paddy fields.

Indeed, Bhutan’s vulnerability to water-induced disasters is well known.  Historically, rivers and streams have overflown their banks, causing destruction. Glacial lakes have burst because of moraine dam ruptures. Bhutan’s sloppy and mountainous terrain makes for easy surface runoff, and the rivers, running through deep gorges and ravines, receive huge volumes of surface runoff during monsoon. All these set up a perfect backdrop for water-induced disasters.

Warming trends and melting glaciers pose serious threats to the nation and its inhabitants. Research reveals that temperatures increase more dramatically in mountain areas, which translates into faster glacier retreat and more glacial lake outburst floods (GLOFs). Further, monsoon variability is now an established fact.

“Bhutan will see more water-induced disasters in the future,” says Karma Dupchu, chief of Hydrology and Water Resource Services Division of the National Centre for Hydrology and Meteorology. “Flash floods are our biggest threat.”

Records show that monsoon brings torrential rains from June to September. In fact, these monsoon rains account for 70 percent of the country’s annual rainfall.

Global warming is the bad guy

Experts say global warming is partly to blame for these heavy rainfalls. This is because warmer air can hold more moisture, which means heavier rains.

Putting global warming in a wider perspective, the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) estimates that by 2100, South Asian countries, including Bhutan, will experience increase in average temperatures, with increases in daily minimum and maximum temperatures, mostly taking place at higher altitudes. A 5 percent decrease in rainfall is expected during the dry season, and an 11 percent increase during the wet season is expected in the long term.

Bhutan does not have records of scientific climate-related data longer than 25 years. Therefore, establishing a mean temperature rise over the last century is impossible. However, the government claims that 2016 was the hottest year in the recent times.

According to a study of 638 years of summer temperature variability over the Bhutanese Himalayas, done by a group of scientists in 2014, the warmest period occurred within the most recent decade, 2004-2013. The scientists (from Bhutan, Sweden, Greece, and the US) warn that Bhutan faces two important and immediate challenges related to climate change.

“Foremost among these threats are altered precipitation patterns and accelerated glacial melt that together trigger mass-wasting events such as landslides, as well as glacial lake outburst floods, endangering life and cultural heritage. Second, increasing variability and unpredictability in stream discharge creates challenges for hydropower generation—which threatens the foundation of Bhutan’s economic security,” states the study.

The secretary of the National Environment Commission, Chencho Norbu, says the other important factor to consider is the loss of vegetation due to development activities. “This exposes our fragile ecosystem to more hazards,” he says, adding that any surface denuded of vegetation eases runoff during rainfall. “That’s why a lot of disasters are human-induced, mainly because of land-use change.”

Chencho Norbu feels field observations and stories from the farming communities are important to validate scientific predictions.

Recent disaster trends

The Asian Development Bank’s (ADB) climate change country risk assessment for Bhutan states that, based on the available evidence, Bhutan will experience more extreme weather events with increased frequency. The ADB identifies flood risk, and particularly flooding from heavy downpours and GLOFs (of 2,794 glacial lakes in the country, 22 are potentially dangerous) as one of the key climate threats for Bhutan. Extreme flood events such as the one in 2016 could become more frequent and severe, putting homes, businesses, and public infrastructure at greater risk.

Bhutan saw a number of significant water-induced disasters in the last 10 years. Three major events stand out: the 2009 Cyclone Aila-induced floods, the 2015 Lemthang Lake outburst flood, and the 2016 southern Bhutan monsoon floods. These disasters not only resulted in the loss of several human lives, but also displaced people and wiped out homes. They caused damage to major public infrastructures, including roads and bridges.

Preparedness, poor but improving

In its 2015 country ranking, the Global Adaptation Institute (GAIN) index places Bhutan at 113th out of 181 countries (with a score of 47.8). The GAIN index further shows that Bhutan ranks 134th (out of 182) in the vulnerability score (higher ranking means less vulnerable) and 91st (out of 185) in the readiness score (again, higher ranking means greater readiness to climate change). Contrast this to Denmark, ranked at number 1, with a score of 81.3, making it the most prepared country in tackling climate change and the least vulnerable to climate change impacts.

Bhutan’s low readiness score is attributed to the country’s “low financial and investment freedom”. Other factors considered in the vulnerability scoring include food capacity where Bhutan’s score reflects the fact that the country has low agricultural technological capacity and high import dependency. To augment this fact, officials from the Ministry of Agriculture say the growth of the agriculture sector has been slow. They attribute the slack to decreasing public investment in agriculture, lack of modern farming technologies, shortage of water for irrigation, and an increasing shortage of farmhands.

However, there is an increasing investment in the area of preparedness. The Bhutanese government is now laying emphasis on developing flood early warning systems along its rivers and building a robust national network of weather stations. Most weather stations have now been automated to provide near real-time information, and a few prediction models are being tested in the selected basins.

The National Centre for Hydrology and Meteorology has a 24/7 monitoring system in place. The centre’s capacity has vastly improved over the years. Some of its staff have been trained in satellite rainfall estimation methods.

“All this is expected to improve weather forecasting,” says Karma Dupchu, adding that flash flood forecasting could still be very difficult.

Accurate estimates of rainfall are needed to forecast floods. Moreover, flash floods are highly localised requiring a close network of monitoring stations. In Bhutan, measuring stations are few and far between, and the available rainfall information is inadequate for forecasting floods with certainty. Moreover, the past events show that flash floods in Bhutan happen mostly in the tributaries where a small babbling brook suddenly turns into a thundering monster sweeping huge boulders and other debris downstream.

For this monsoon, the centre predicts a fairly good amount of rain, mostly in the form of high-intensity short-duration showers.

“This kind of rainfall pattern is often responsible for flash floods, but we cannot say for certain if there will be flash floods this monsoon,” says Karma Dupchu. “We will stay alert and try our best to communicate to the public whatever information we can generate.”

Gopilal Acharya is an independent consultant and a freelance journalist. 

He can be contacted at

gopibhutanese@gmail.com

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