Mitigating Cloudbursts Need Better Forecasting and Disaster Preparedness

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Cloudbursts in recent times

On July 19, 2017, a cloudburst in the Chenab Valley region of Doda district in Jammu and Kashmir led to 8 deaths and 11 people injured (The Hindu, 2017). Many of the casualties occurred due to running debris and silt that flowed through in the Chenab Valley as a result of the night-time cloudburst between July 19 to the 20. Flash floods hit Thathri town at 2 in the morning. The deaths mostly occurred as most people were asleep during the cloudburst. The Batote-Kishtwar highway was also struck by a flash flood due to the cloudburst where there was significant property damage. Earlier in the month on July 1, a cloudburst over Morbi district in Gujarat had led to floods that had displaced over 1,500 people (Indian Express, 2017). Uttarakhand, lashed by a cloudburst-induced landslide disaster in 2013, is on alert and tourists have been advised not to travel to Uttarakhand after spells of very heavy rainfall were recorded during the 2017 Monsoon.

Understanding Cloudbursts

The definition of a cloudburst is not ambiguous, and there is a proper method whereby very heavy rainfall that takes place over a short period of time and over a limited area is classified as a cloudburst. If the rainfall recorded over an area measuring approximately 20 to 30 sq km falls at a rate of 10 cm per hour (or above), the Indian Meteorological Department (IMD) defines the rainfall event as a cloudburst (IMD, 2017).

Cloudbursts are known to frequently trigger flash floods and landslides, making cloudbursts especially dangerous in mountainous regions. The flash floods triggered by cloudbursts are more difficult to mitigate due to their suddenness and can be especially dangerous in compact and enclosed spaces on slopes such as those of mountainous cities and towns. The leeward front presented by clusters of mountains make mountainous regions more susceptible to cloudbursts than plain areas.

Cloudbursts are usually made up of saturated clouds accompanied by the upward movement of warm currents of air. This causes large accumulations of heavy raindrops in the cloud that are bolstered by the updraft until they coalesce together and become too heavy for the cloud to hold. When this heavy accumulation of raindrops finally precipitate due to significant temperature differences, they suddenly fall in a bulk, and in such a case there is a chance of a cloudburst occurring. Mountainous terrain aids in the upward movement of warm air currents, and thus increases the likelihood of cloudbursts over these regions.

According to Dr Ajit Tyagi, former Director General of IMD, the “Only difference between heavy rainfall and cloudburst is intensity of vertical motion in a small area. This takes large water droplets and ice crystals upwards and the vertical motion is not able to keep the huge quantity of piled up hydro meteors afloat. Thus large droplets start falling in the form of very heavy rainfall within a short period of time resulting in cloudburst like situation.

“In Plains it occurs with intense meso-scale circulation and strong upper level divergence. Being a highly localized phenomenon,  it is difficult to forecast exact location and time of cloudburst occurrence. These generally occur during active  monsoon conditions and at best can be detected by Doppler Weather Radars. As there are no radars and denser Automatic Weather Stations in Himalayas, cloudburst events are generally reported based on loss of life and damage in a given small area and not based on Meteorological data” he adds.  “Cloudburst studies require high quality meso-scale meteorological/thermodynamical data which is not available at present to scientists. For this there is need to have special observation campaign”, Dr Tyagi opines.

The UN Global Environmental Outlook (GEO-6): Regional Assessments report (2016) places India as among the countries that might be most affected by the effects of climate change. The UN expects that about 40 million people in India in 2050 might be affected by rising sea levels.

The state of Jammu and Kashmir in India has witnessed several cloudburst events since the cloudburst in Leh in 2010. Dr Shakil Ahmad Romshoo, head of department of earth sciences, University of Kashmir  comments that “Cloudbursts are becoming highly localised. Conditions across the Himalayas, including in J&K, are changing and witnessing extreme weather events. Heavy rain, a rare phenomenon in Kashmir and Ladakh, is now a reality.” Also, as the region is a seismic zone, landslides triggered by earthquakes are an imminent threat (S. Hakhoo, 2015). Globally, monsoons have displayed diminishing intensity since 1950, as assessed in a paper by Chase et al. in 2003. Although there is no evidence to link global warming directly with variances in the monsoons overall (Chase et al, 2003), the most significant trend is the increasing incidence of local heavy rainfall, cloudbursts and floods while the overall monsoons are deficient in intensity.

Disasters due to Cloudbursts and its Mitigation

The most devastating disaster in India due to cloudbursts was the Uttarakhand floods and landslides of 2013, which were preceded by heavy rainfall before a cloudburst that triggered flash floods. The total death toll was about 5,700 deaths, making it the 5th deadliest global landslide event in terms of fatalities. Another significant cloudburst event was a cloudburst during the Monsoons on August 6, 2010, which triggered flooding and landslides in the Himalayan region of Ladakh in Jammu and Kashmir that claimed at least 257 lives (NDMA, 2015).

Other notable recent cloudburst incidents include the Shimla, Himachal Pradesh cloudburst (2016) where flash floods led to the disappearance of 4 youths; the Dharampur, Himachal Pradesh (2015) cloudburst causing 4 deaths; 8 cloudbursts in 3 weeks in the Kashmir Valley (2015) that left 10 people dead; and 1 death and 5 injured casualties in a cloudburst in Tehri district in Uttarakhand (2015) (Indian Express, 2016).

With cloudbursts occurring with greater frequency over certain regions of the country and the resulting flash floods and landslides sometimes leading to huge death tolls, making them national tragedies, we must offer cloudbursts greater space in our discourse. Rescue and relief and evacuations cannot be enough due to the sudden nature of the disaster. The best solution has to be a solution inbuilt into our habitations whereby the effects of cloudbursts can be mitigated therein. One such mechanism is being planned in the city of Copenhagen, Denmark.

A useful model in cloudburst mitigation is Copenhagen, whose municipal department has organized a cloudburst masterplan coupled with concretization plans. The plan is expected to be fully implementable in about 30 years time. The plan is envisioned with a view to cope with the effects of climate change and chiefly aims at fixing acceptable limits of flooding in the streets (tentatively fixed at 10 cm). The plan aims to decouple 30 to 40 per cent of the excess storm water from the combined sewer system to level out the expected 40 per cent excess rainfall due to climate change over a 100 year period. The plan incorporates both concretization, creation of canals and the greening of Copanhagen (M. Vilmhelmsen, 2016). Copenhagen represents the way forward in long term planning for some of the aberrations that might be caused by climate change. An inbuilt mechanism to combat a disaster is the best solution, provided it delivers.

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