Glacier Lake Outburst Floods in Reshun Valley of Pakistan

Fact or Fantasy

Glacier outburst floods may be broadly defined as the sudden release of water stored either within a glacier or dammed by a glacier (Fountain and Walder, 1998). Outburst floods have been reported in all glaciated regions of the world and may be triggered by:

  1. The sudden drainage of an ice-dammed lake below or through an ice dam;
  2. Lake water overflow and rapid fluvial incision of ice, bedrock or sediment barriers; or
  3. The growth and collapse of subsurface reservoirs (Benn and Evans, 1998).

Due to their high and rapid discharge, the outburst floods originating from high mountain/alpine glaciers have devastating impacts on downstream communities. Chitral is largest District of Khyberpukhtunkhwa Province of Pakistan and is located at about 365 Km in the north of provincial capital Peshawar at the foothills of Hindukush Mountain Range. The entire district is comprised of lofty mountains. The climate of Chitral is dry temperate and the bulk of precipitation is received during the winter. The months from June to the end of August are usually dry.

Chitral has a very long history of glacier outburst floods or glacial lake outburst floods (GLOF). The largest known glacier outburst flood within the now district Chitral of Khyberpukhtunkhwa occurred some 350 years back and originated from Chiantar Glacier in Broghil valley. But in present times with the onset of twenty first century both the intensity and frequency of GLOF events in Chitral have increased many folds.

The Chitral district is home to about 542 glaciers covering a total area of 1904 (nearly 13% of the total covered area of the district). Of these, 187 glaciers have developed glacial lakes. However, no substantial research has been undertaken to evaluate the exact status and number of potentially dangerous glacial lakes in the district. It is commonly believed that there are more than 20 potentially dangerous glacial lakes in different valleys of the district including the Golain, Laspoor, Yarkhoon, Terich, Reshun valleys. With the beginning of the 21st century the glacial outburst floods have gained momentum in District Chitral. Over a period of 12 years the district has experienced more than 8 glacial outburst floods in different valleys. The glacial outburst floods in Yarkhon Lasht (2003), Brep (2005), Sonoghor valley (2007), Bindo Gol (2010), Boni (2011) and recently in Reshun valley (2013) are recent examples. The village of Reshun was struck by a devastating flood in Reshun stream on July 31, 2013. Weather conditions prevalent in the area and other geo-climatic evidences substantiate that the flood was of glacial outburst origin. This outburst flood caused heavy damages to infrastructure and local livelihoods.

Glacier fed river systems are the life line of the Pakistani economy. The contribution of glaciers to fresh water system is more than 60% of the total in Pakistan. It is believed that glaciers have persisted in Hindu Kush-Himalayas of Pakistan since the last Ice Age, which occured about 15,000 years ago. Today most glaciers are found in Antarctica and Greenland. But outside the polar region, the Hindukush-Himalayas regions are the most heavily glaciated areas in the world. Hindukush-Himalayas region are an abode to some 15,000 glaciers, cradle to 9 major glacier-fed river systems and home to 1.9 billion people in the world.

The river systems originating from these glaciers provide life sustaining water and hydroelectricity to almost one-third of the world’s population. The Northern Areas of Pakistan including Gilgit-Baltistan province and Chitral host at least 5218 glaciers. These glaciers feed ice melt water to the Indus River System. Of these glaciers about 2420 have developed glacial lakes and nearly 52 glacial lakes in Northern Pakistan have been classified as potentially dangerous. Recent research reveals that glaciers in Pakistan are retreating at a rate of almost 40 to 60 meters per decade. This a very alarming situation and needs the immediate attention of researchers and Disaster Management authorities. This climate change induced melting of glaciers in mountainous areas like Chitral is not only leading to unprecedented disasters, damaging lives and livelihoods of local and downstream communities, but resulting in shrinkage of ice-stored reserves of drinking and irrigation in waters.

Case Study: (Glacier Outburst Flood in Reshun Valley, Chitral)

The historical village of Reshun is located in the north of main town Chitral at a distance of 55 km between 360 09′ 21.88″ N 720 06′ 03.16″ E. The village is comprised of 8 small and big hamlets. There are about 800 (estimated) households accommodating a population of about 7000 souls. The Reshun village is located on the western bank of River Chitral on main Chitral Mastuj Road. The average elevation of the village from sea level is about 6225FT. Reshun is famous for its nutritious fruits, cultural activities, Honey production and enchanting landscape. Orchard raising, livestock, agriculture supplemented by localized trade and employment in both public and private sectors are the main sources of livelihoods. One of the main land features in Reshun valley are “Glaciers” situated at an elevation of about 1400 ft above sea level.

1. Facts and Figures:

Above the Reshun village there are two main glaciers located some 14000 ft above sea level. Both are the glaciers are separated by a mountain ridge. The Glaciers are of D-type (debris covered). The glacier located on the eastern basin of the ridge (facing the sun) is about 4.6 km in length and its average width is nearly 0.8 km. Both glaciers are located in close proximity to each other between 360 08′ 52. 84″ N and 720 14′ 38. 86″ E. Aerial pictures of the glacier indicates the presence of at least seven supra glacial lakes of varying sizes on both glaciers. However, the eastern glaciers has developed more lakes as compared to western. The western glaciers is divided into two lobes. The average length and span of the western glacier is approximately 3 km and 0.5 km respectively. The terminal moraines of both glaciers shows breaches at many points. Presence of the surface lakes coupled with highly fragile terminal moraines make both the glaciers potentially dangerous source of outburst floods. Location of these glaciers at high elevation in relation to the downstream communities further make them even more dangerous. In times of outbursts floods and in absence of sophisticated early warning system, the downstream communities of Reshun village will have very little time to quickly respond to fast coming disaster. There is a hot debate among researchers and academics that whether, the floods in Reshun were GLOF in nature or not. In depth analysis of the physical aspects of Reshun Glaciers, weather conditions during the month of July, 2013, geological aspects of the Reshun valley and seismic activities, which Chitral district experienced, during the same month support the fact that the recent flood in the Reshun valley was GLOF in nature. Although as per preliminary assessment it is a mere assumption but this assumption is supported by following geo-climatic facts:

A. Physical Conditions of Reshun Glaciers:

Both the glaciers above Reshun valley seem to be highly unstable. This due to the facts that:

  1. The glaciers are located on steep slopes supported by fragile moraines.
  2. Aerial pictures of the glaciers indicate that the terminal moraines are breached at many points making the moraines even weak to sustain increasing hydraulic pressure from inside or exerted by the supra glacial/tarns lakes.
  3. Both glaciers, especially, the glacier on the eastern side contains number of supra glacial and tarns lakes.
  4. Reshun valley is located on Reshun Fault which furthers adds to the geological instability of the valley.

B. Weather Conditions during the month of July, 2013:

The weather conditions and trends for the month of July are given as below in tabulated form:

Month

Mean Minimum
Temperature

Mean Maximum
Temperature

Rain fall
(MM)

July 2010

35 0C

18 0C

63.2 MM

July 2011

20 0C

36.3 0C

Nil

July 2012

19 0C

37.4 0C

Nil

July 2013

21 0C

38 0C

4 MM

Source:
Pakistan MET office Chitral

The above data shows that July, 2013 remained slightly  hotter as compared to preceding years of 2010, 2012 and 2011. However the difference in daily range of temperature from July 19 to 31, 2013 was very significant as compared to previous years.  From July 19 to 31, 2013 the average minimum temperature in Chitral was recorded 23 0C while the mean maximum was 39 0C. On July 28 and 29, 2013 the minimum temperature was recorded 26 0C.

C. Seismic activities/earthquake events:

During the month of July, 2013 the Hindukush region in proximity of district Chitral also experienced multiple numbers of earthquakes and seismic activity of varying magnitude. The details are given as below:

S#

Date

Magnitude
on Richter Scale

Location

1

July 14, 2013

4.1

Hindukush

2

July 20, 2013

3.6

Hindukush

3

July 21

5.2

(HK) North West
of Chitral

4

July 26, 2013

4.5

HK

5

July 28, 2013

4.1

HK

6

July 29, 2013

5.3

HK

Source: http://www.pmd.gov.pk/

The entire month of July (2013) experienced earthquake events of different magnitude. In fragile mountain ecosystem earthquake/seismic
activities are considered as one of the potential reasons leading to Glacial Lake Outburst Floods.

The strong heat wave generated during the last two weeks of July coupled with physical vulnerable features of the glaciers, earthquake events during the same month supports the idea that the recent floods in Reshun valley were of GLOF origin.

However, over the past one decade the district of Chitral has been experiencing somewhat unusual weather conditions characterized by off-season rain, cloud bursts, thunderstorms etc. The second and last weeks of the month were full of extraordinary weather conditions. However, during the month of July, 2013 only 4 millimeter of rain was recorded in Chitral. Such a meager amount of rain fall is hardly sufficient to cause Glacial Lake Outburst Floods (GLOF) forcing moraine breach or overflow of glacial lake. This further supports the assumption that Glacier outburst flood in Reshun was probably triggered by strong heat wave, generated during the month of July, 2013.

Reshun valley, was hit by glacial outburst floods (GLOF) on July 31, 2013. The impacts of this flood was devastating. Nearly 40 houses, 20 shops, 30 animal corrals, standing crops and orchards were wiped away in a blink of eye by glacial outburst flood that may have originated from Reshun Glaciers located at an elevation of 13800 feet above sea level. Two ill-fated human lives also fell prey to the flood as well. One jeep-able and two pedestrian bridges were also completely destroyed and mobility of the up and downstream communities were badly impaired. Transmission lines and channel of the hydle power station were also badly damaged.

Irrigation channels and potable water supply schemes were also damaged. Heads of 3 main irrigation channels were completely destroyed. Standing crops and agriculture lands were also destroyed. A detail assessment of the damages will be undertaken after consulting district administration and other stakeholders.

Findings/Conclusion

Weather conditions for the past one decade indicates that temperature of the district has increased slightly. The district, during the year 2013 received nominal amount of precipitation in summer spell to trigger floods. This suggests that flood in the Reshun valley was of GLOF origin.

  1. Huge glaciers are present in Reshun that can trigger outburst floods with slight temperature increases.
  2. The location of Reshun on seismically active area further makes it vulnerable to glacier outburst floods.
  3. Over and uncontrolled grazing of livestock in pastures located in proximity to glaciers Extensive deforestation in forested areas in Reshun valley which is leading to reduced Sinks for Green House Gases.
  4. Based on the discussion and facts above it is irrefutable the glaciers outburst floods are facts not fantasy.

Hamid Ahmad Mir is the Manager of the Pakistan GLOF-Project, District Chitral, Pakistan. He can be reached at: hameedwwf@hotmail.com. Read other articles by Hamid.