Cloud Burst and Flash-Floods: A Climatic Threat in the Western Himalaya

Deliberations about mountains and climate change are characterized by a clear focus on the impacts of global warming on high altitude environments and on the respective adaptation strategies of mountain dwellers. In recent decades, rising temperatures, change in timing, location and amount of rain, increased frequency of cloud bursts and flash-floods, retreating glaciers, and reduced snow cover together indicate change in the natural climate of the western Himalaya. The impacts of climate change can be more severe in the Himalayas than other parts of the subcontinent because local climates in different elevations fluctuate between warm and cold regimes. Scientific predictions point out that the Himalayan region has been experiencing warming at a greater pace (almost three times) than the global average of 0.74°C over the last 100 years. IPCC predicts that average annual mean temperature over the Himalayas will increase by about 3 ⁰C by 2050 and about 5 ⁰C by 2080. The average rate of increase of temperature is higher in the eco-regions of the higher elevations. Overall annual temperatures in the Himalayas have recorded significant increase in the last century.

Flooded Srinagar town of Uttarakhand during 16 and 17 June, 2013, disaster 

Intense rainfall is the most common cause of flash-floods in the region. These events may last from several minutes to several days and may happen anywhere, but are more common in mountain catchments. The main meteorological phenomena causing intense rainfall are cloudbursts, a stationary monsoon through, and monsoon depressions. A flood regime is a historically experienced pattern of variability in onsets, durations, extents and frequencies. Flood regimes are affected by several factors including regulation of rivers, land, water uses and climate. Retreating glaciers often leave behind voids that are filled by melt water and are called glacial lakes. Glacial lakes can burst due to internal instabilities in the natural moraine dam retaining the lake (for example, collapse due to hydrostatic pressure, erosion, overtopping, internal structural failure) or due to external triggers such as rock/ice avalanche, earthquake, and so on. These catastrophic processes are known as glacial lake outburst floods (GLOFs). A GLOF can result in flow of water and debris several orders of magnitude greater than seasonal high flow. Western Himalaya has suffered a number of GLOFs in the past.

Flooded Srinagar town of Uttarakhand during 16 and 17 June, 2013 disaster

Threats from Cloud Burst and Flash-Floods

In connection with global climate change on the Earth the number of catastrophic floods has been enormously increased and caused great damages. Insurance against the impact of flooding would therefore benefit a significant proportion of the global population and yet much of the worldwide flood damage remains uninsured. Rising extensive impact on urban system associated with climate related disasters are particularly noticeable in the past 30 to 40 years. Losses of human life and properties are increasing, especially in vulnerable human habitats where different challenges coincide: limited insurance converge, inappropriate planning practice, rapid urbanization following population growth and migration leading to land scarcity and informal settlements. Extreme rain events during summer monsoon cause severe hydro meteorological disasters across western Himalaya. According to the National Commission on Floods, more than 40 million hectares of land in India (total geographical area, 329 million hectares) is prone to floods. Every year, more than 7.5 million hectares of land is affected, and 1,600 lives are lost. As urban population and infrastructure have increasingly expanded in river flood lands, losses and fatalities from cloud burst and flash-floods have become common occurrences.

Debris deposition inside the ITBP camp at Srinagar town  

Extreme rainfall events, landslides, debris flows, torrents and flash floods due to failure of natural dams and glacial lakes outburst are the main types of natural hazards in the Himalaya. In most cases, these natural disasters are triggered by extreme weather conditions (high or extreme rainfall events) during monsoon period. Mountain areas are early indicators of climate change. The Himalayan Mountain is particularly susceptible to impact of climate change because of their young and fragile nature coupled with sharp biophysical gradients.
   

Debris deposition inside the  Bhyundar village of Uttarakhand

Earth surface processes such as landslides, rock falls, debris flows, floods, and accelerated erosion and snow avalanches pose a risk to life and property in high mountain environments. Entire Himalayan region is vulnerable to torrential rainfall hazards in the form of flash flood, cloudburst or glacial lake outburst flood. Flash floods and cloudburst are generally caused by high intensity rainfall followed by debris flow or landslide often resulting into blockade of river channels.

Flash Floods and Cloud Burst on 16-17 June 2013

Uttarakhand and Himachal Pradesh, two hill states in the western Himalayan range, are so far the worst hit by the extreme rains that struck northern India in the wake of monsoons that set in June, 2013. Alaknanda and Bhagirathi basin of Uttarakhand, particular have experienced one of the worst forms of disaster at 16 and 17 June.  Disaster was a natural or man-made hazard resulting in an event of substantial extent causing significant physical damage or destruction, loss of life, or drastic change to the environment. The constant rains for 72 hours have endangered the normal life. Usual unprepared villages suddenly had to face the disaster; many were swept away in sleep. Most of the roads in the region are damaged. Various Government buildings and bridges along the riverside have been swept away with violent river flow.

Impact Highlights

People affected	Infrastructural Damage	Environmental Stress
Estimated death toll of 5000, and 4700 missing across Uttarakhand; Estimated 1, 10,000 people evacuated so far.	600 villages across Uttarkashi, Chamoli, Rudraprayag, Pithoragarh districts have had severe damage (washed away/submerged).	25-30 million tourists/pilgrims visit Uttarakhand each year, which is 2.5 times the population of the entire state.
Severe impact on livelihood; 19,590 business establishments devastated which translates to loss of over INR 5300 million.	760 villages were absolutely cut off. Limited/intermittent road connectivity to reach supplies to 13,600 villages. 1,000 Bridges damaged.	60 hrs of cloudburst & continuous rain, leading to 330 mm of rain.
16 lakh people affected. 30,000+ households in severely affected villages are in dire need of food, water, shelter, medicines. Several injured, and threat of epidemics.	37,000 sq. miles area affected. Loss to economy is INR.30, 000 million. 300+ villages face severe drinking water shortage; Primary Health Centres facing shortage of medicines.	70 Hydroelectric projects in worst affected Char Dham area; 505 dams in Uttarakhand state. 4,640 cases of illegal mining

Source: (Pragya 2013)

Climatic Intervention

Natural disasters in western Himalaya result from the combinaction of the following natural factors: continuous rainfall and cloud  bursts,  snowmelt and rainfall combine, galcial lake outburst and breaking of dam caused by lanslide falling directaly into the river. Flash-flood is a sudden, localized flood of great magnitude and short duration, typically caused by heavy rain. Most flash-floods are local events which are relatively independent of each other and scattered in time and space. Flash-foods are also severe flood events triggered by extreme cloudbursts; glacial lake outbursts; or the failure of artificial dams or dams caused by landslides, debris, ice, or snow. Rapid melting of snow accumulated during winter and heavy rainfall in high altitude are the main causes of flash floods and glacial lake outburst in the western Himalayas. Furthermore, the region is experiencing widespread deglaciation, most probably as a result of global climate change. Moreover, others hazards such as avalanches and landslides occur exclusively in the western Himalaya. There are numerous instances of recent disasters caused by heavy rainfall in the hilly terrains of the Himalayas.  In the western Himalaya, frequencies and intensity of flash floods and cloud burst events are found to be increasing continuously. 
    

Washed out road of  Govind Ghat during flood

The western Himalaya is prone to climatically induced hazards of various forms and nature, like cloud bursts and flash-floods. However,  there are sign that not only the frequency of such hazards is increasing with time but also their intensity and impact on lives and livelihood of people, living in the area, is incresing in severity. Over the years, incresed frequency and magnitude of flash-floods in the western Himalya is worrying the inhabitants.  In June, 2013, we witnessed the incidents of cloud bursts and flash-floods in the region (different places of Uttarakhand and Himachal Pradesh). Today, the western Himalaya; its mountains, rivers and people are in a state of crisis, being rapidly encroached upon in many ways. Climate change and the pressures on its resources for economic growth are challenges on a scale never seen before. As urban population and infrastructure have been increasingly expanded in river flood land areas, losses and fatalities from cloud burst and flash-floods have become common occurrences.  We have witnessed the Himalayan Tsunami which happened on 16th and 17th June, 2013, in Uttarakhand and Himachal Pradesh, which could be the sign of a greater ensuing climatic disaster.