**4.2 GLOF events associated with surging of glaciers**

*Glaciers and the Polar Environment*

Kunming, China, and ICIMOD. The remote sensing and field observations

**Year Event date Glacier River Influencing factors**

1999 6 August Khalti/Gupis Gilgit Moonsoon rainfall 2000 10 June Shimshal Hunza High temperature 2000 27 July Kand/Hushe Indus Moonsoon rainfall

 5 April Ghulkin Hunza Western disturbance 6 January Passu Hunza Western disturbance 2 April Ghulkin Hunza Western disturbance 22 May Ghulkin Hunza Persistent rainfall 24 May Ghulkin Hunza Persistent rainfall 14/15 June Ghulkin Hunza Heat wave

2009 26 March Ghulkin Hunza Western disturbance

2018 17 July Barsuwat glacier Immit Heat wave 2019 23 June Shishper Hunza High temperature 2020 29 May Shishper Hunza High temperature

 — Batura Hunza — — Batura Hunza — — Balt Bare Hunza — September Darkot/Barados Gilgit — July Sosot/Gupis lake Gilgit —

2005 July Sosot/Gupis lake Gilgit

analysis of Khurdopin glacier provides up to date evidence about glacier surge and its possible impacts on the downstream populations because of the newly devel-

Glacial lakes formation depends on the type of glacier, its slope, and geological settings. For example, a supraglacial lake creates on the surface of glaciers when its slope is less than 2%. Similarly, surging glaciers block the river valley and cause the formation of the lake. Moreover, moraine-dammed lakes develop due to the advancement or recession of valley glaciers. Overall, these GLOF events depend on the physical and topographical conditions and the nature of damming materials. The severity of damages increases as the elevation and the volume of the glacial lakes increases. The type of moraine-dammed and the surging glaciers are the most dangerous types that block the valleys and cause GLOF events in the basin. In this regard, the type of GLOF event for the glaciers in the Hunza Basin is also not the same for example; Passu glacier caused damage due to outbursts of the end-moraine dammed lake, supra-glacial lake outburst occurred from Ghulkin and Hispar glaciers, valley blocked by Khurdopin glacier. GLOF from these glaciers bring rocks and the mudflows in the glacial streams,

for example, significant mudflows released from Batura glacier.

**110**

oped lake.

**Table 2.**

**4. Results and discussion**

**4.1 GLOF events in Hunza basin**

*History of major GLOF events in CPEC region.*

The surging activities of the glaciers in the Hunza Basin have also been interpreted by earlier studies [14, 32, 33] from a stable or slightly increasing trend of snow cover for the Hunza River basin [1, 25]. It has been reported recurrent surges for several glaciers of the Hunza Basin [6]. For example, Bolch et al. [20] and Quincy and Luckman [34] have comprehensively reported the surge history of Khurdopin glacier. The glaciated area of Khurdopin glacier is 115 km<sup>2</sup> which is situated in Shimshal River, a tributary of the Hunza River. The first surge has been reported in 1979 and the second surge event occurred in 1999 and both surge events occurred in the summer season. The latest surge was observed during the summer season of 2017 [35]. These events suggest the return period of the surge event for Khurdopin glacier is about 20 years. No significant change has been observed in the debris cover Hispar and Shimshal glaciers of the Hunza basin for the period of 1977–2014 [36]. It was determined that this might be due to balanced glacier budgets during this period. Type of glaciers and their areas are given in **Table 1**.

The surging of Khurdopin glacier has resulted in the formation of the mediumsized ice-dammed lake at an elevation of 3454 m a.s.l and it lies at latitude-longitude of 36°21′007″ N and 75°27′51.2″ in the Shimshal River valley of the Hunza basin. Khurdopin lake started to surge in the first week of May 2017 and it has been greatly expanded in terms of size and depth and it became vulnerable to breach as witnessed by the local people. Due to the short distance between the glacier and opposite hard mountain resulted in the rise of river bed and glacier as well as triggering the creation of Khurdopin lake. The velocity of the flow was reduced by the damming of water behind the barrier and this phenomenon also raised the river bed and blocked the river (**Figures 2** and **3**).

**Figure 2.** *Comparison of different glaciers area loss during the period of 1977–2014.*

#### **Figure 3.**

The glacier areas of different glaciers were compared, which mostly thinned in terms of area or remain constant during the different periods. The area of Batura glacier was 380 km<sup>2</sup> in 1977 as compared to 351 km<sup>2</sup> in 2014, respectively. The loss of the area was 7.63% during this period. However, the glacier area loss was observed about 4.69% between 1999 and 2014. The glacier area was reduced to 369 km<sup>2</sup> till 1999 and lost 2.89% of the glacier area as compared to 1977. The loss in glacier area was increased by up to 7% in 2014 as compared to 1999. The increment of a 4% loss in glacier area was due to an increase in temperature. During 2001 and 2007, the loss of glacier area was consistent, but it was observed 4.2% in 2009 as compared to 1977. Passu glacier area loss observed 10% from 1977 to 2014. The loss of the area was less than 1% for 1999 as compared to 1977. The rate of loss of the glacier area increased in 2001 and reached up to 3% but this rate reached up to 7% in 2007. The lake formation also fluctuated during this period. The number of GLOF and historical events was also observed during this period. Ghulkin glacier also lost its area up to 4% due to global warming from 1977 to 2014. Earlier 2000, Ghulkin glacier lost the area less than 1.5%. After 2 years, the loss of the glacier area was 6%. From 2001 to 2007, the melting of glacier and loss of its area remained constant but the rate of glacier area loss was reduced up to 4% in 2009. Ghulmit glacier lost its area about less than 2% before 2000. The loss of the glacier area in 2001 was 4% but it increased up to 5% in 2007. This glacier area was reduced to 3% in 2009 as compared to 2007 (**Table 3**).

#### **4.3 Drifting mechanism of glaciers**

Due to differential movement of glaciers, crack or rift is produced in the glaciers having connected snout. A rift was formed along the left part of the Khurdopin glacier due to collapsing and crushing of glacier all together. The Yukshin Girdan glacier played a role of strong obstruction, produced massive frictional forces, and initiated the glacier ice to break down at the rift area into pieces of ice bergs that were seen floating on the newly formed lake. During this process, the Khurdopin glacier was forced by the Yukshin Girdan glacier to move toward the right side because of the unavailability of an obstacle to the opposite mountain. The elevation of the glacier at the rift area was about 3558 m a.s.l. The glacier was covered by a huge amount of debris during 2015, and after this surge, the debris began to falling

**113**

*Risks of Glaciers Lakes Outburst Flood along China Pakistan Economic Corridor*

4 Hispar Surge type

6 Khurdopin Debris cover

7 Vijerab Debris cover

*List of selected glaciers and their types in Hunza basin [20].*

**Sr.# Glacier name Glacier type Area (km2**

Debris cover

Surge type

Surge type

1 Batura Debris cover 236 2 Passu Debris free 51 3 Barpu Surge type 90

5 Yazghil Debris cover 99

**)**

345

115

113

and sliding into the crevasses and impacted the sub-glacial water movement and that may further result in the formulation of a new sub-glacial lake [25, 34].

Whole region 2868

The meltwater released from the Vijerab glacier was blocked by the Khurdopin glacier and it was muddy because of high sediment load coming from the glaciated area. A large amount of water was flowing through the newly developed crevasses due to the presence of barriers and ultimately outflowing through the cave type snout of Khurdopin glacier. The phenomenon of ice block falling in the stream of Vijerab glacier and on the supra-glacial lakes was also perceived. Because of surging effects, glacier deforms and results in the formation of huge crevasses. Three main types of crevasses developed in Khurdopin glacier are listed below: irregular crevasses, longitudinal crevasses, and transverse crevasses. Due to the demolishing action of glaciers, most of the crevasses were found to be irregular in shapes. Due to glacier advancement, large numbers of crevasses were developed all over the glacier. The width of the crevasses was variable at different locations and mostly, it ranged

The heterogeneous behavior and close-to balanced budgets are not a recent phenomenon in Hunza Valley (Karakoram). We have observed that the geodetic mass budgets computed from the 1973 KH-9 and 2009 ASTER DTMs are in covenant with the results of the individual periods 1973–1999 and 1999–2009 without indefinite radar penetration correction: since the 1970s, the glaciers in this region underwent slight and insignificant mass loss. Though, the differences may exist in individual glaciers for the two studied periods. Overall, we can confirm that the surge-type and non-surge-type glaciers are not significantly different with respect to mass change inferred from the 40 years observations of glaciers in the

One can easily assess the flood damages from recently developed lakes if it bursts based on watermarks of previous flood events. Besides, the bursting mechanism and the volume of flood events can give us an insight into the damages in the downstream areas. The water level in the lake can provide us information about the GLOF impacts on downstream infrastructure. The GLOF will have devastating impacts on the infrastructure including homes, lands, schools, etc. The settlement along the

river site could be adversely affected as a result of GLOF (**Figure 5**).

*DOI: http://dx.doi.org/10.5772/intechopen.93459*

between 1 and 2.0 m [20, 35].

**Table 3.**

Karakoram (**Figure 4**).

**4.4 Geodetic mass balance of surging glaciers**

*Risks of Glaciers Lakes Outburst Flood along China Pakistan Economic Corridor DOI: http://dx.doi.org/10.5772/intechopen.93459*


#### **Table 3.**

*Glaciers and the Polar Environment*

glacier was 380 km<sup>2</sup>

in 2009 as compared to 2007 (**Table 3**).

**4.3 Drifting mechanism of glaciers**

369 km<sup>2</sup>

**Figure 3.**

The glacier areas of different glaciers were compared, which mostly thinned in terms of area or remain constant during the different periods. The area of Batura

till 1999 and lost 2.89% of the glacier area as compared to 1977. The loss in

loss of the area was 7.63% during this period. However, the glacier area loss was observed about 4.69% between 1999 and 2014. The glacier area was reduced to

glacier area was increased by up to 7% in 2014 as compared to 1999. The increment of a 4% loss in glacier area was due to an increase in temperature. During 2001 and 2007, the loss of glacier area was consistent, but it was observed 4.2% in 2009 as compared to 1977. Passu glacier area loss observed 10% from 1977 to 2014. The loss of the area was less than 1% for 1999 as compared to 1977. The rate of loss of the glacier area increased in 2001 and reached up to 3% but this rate reached up to 7% in 2007. The lake formation also fluctuated during this period. The number of GLOF and historical events was also observed during this period. Ghulkin glacier also lost its area up to 4% due to global warming from 1977 to 2014. Earlier 2000, Ghulkin glacier lost the area less than 1.5%. After 2 years, the loss of the glacier area was 6%. From 2001 to 2007, the melting of glacier and loss of its area remained constant but the rate of glacier area loss was reduced up to 4% in 2009. Ghulmit glacier lost its area about less than 2% before 2000. The loss of the glacier area in 2001 was 4% but it increased up to 5% in 2007. This glacier area was reduced to 3%

Due to differential movement of glaciers, crack or rift is produced in the glaciers having connected snout. A rift was formed along the left part of the Khurdopin glacier due to collapsing and crushing of glacier all together. The Yukshin Girdan glacier played a role of strong obstruction, produced massive frictional forces, and initiated the glacier ice to break down at the rift area into pieces of ice bergs that were seen floating on the newly formed lake. During this process, the Khurdopin glacier was forced by the Yukshin Girdan glacier to move toward the right side because of the unavailability of an obstacle to the opposite mountain. The elevation of the glacier at the rift area was about 3558 m a.s.l. The glacier was covered by a huge amount of debris during 2015, and after this surge, the debris began to falling

in 2014, respectively. The

in 1977 as compared to 351 km<sup>2</sup>

*Temporal variation in areas of different glaciers along CPEC.*

**112**

*List of selected glaciers and their types in Hunza basin [20].*

and sliding into the crevasses and impacted the sub-glacial water movement and that may further result in the formulation of a new sub-glacial lake [25, 34].

The meltwater released from the Vijerab glacier was blocked by the Khurdopin glacier and it was muddy because of high sediment load coming from the glaciated area. A large amount of water was flowing through the newly developed crevasses due to the presence of barriers and ultimately outflowing through the cave type snout of Khurdopin glacier. The phenomenon of ice block falling in the stream of Vijerab glacier and on the supra-glacial lakes was also perceived. Because of surging effects, glacier deforms and results in the formation of huge crevasses. Three main types of crevasses developed in Khurdopin glacier are listed below: irregular crevasses, longitudinal crevasses, and transverse crevasses. Due to the demolishing action of glaciers, most of the crevasses were found to be irregular in shapes. Due to glacier advancement, large numbers of crevasses were developed all over the glacier. The width of the crevasses was variable at different locations and mostly, it ranged between 1 and 2.0 m [20, 35].

#### **4.4 Geodetic mass balance of surging glaciers**

The heterogeneous behavior and close-to balanced budgets are not a recent phenomenon in Hunza Valley (Karakoram). We have observed that the geodetic mass budgets computed from the 1973 KH-9 and 2009 ASTER DTMs are in covenant with the results of the individual periods 1973–1999 and 1999–2009 without indefinite radar penetration correction: since the 1970s, the glaciers in this region underwent slight and insignificant mass loss. Though, the differences may exist in individual glaciers for the two studied periods. Overall, we can confirm that the surge-type and non-surge-type glaciers are not significantly different with respect to mass change inferred from the 40 years observations of glaciers in the Karakoram (**Figure 4**).

One can easily assess the flood damages from recently developed lakes if it bursts based on watermarks of previous flood events. Besides, the bursting mechanism and the volume of flood events can give us an insight into the damages in the downstream areas. The water level in the lake can provide us information about the GLOF impacts on downstream infrastructure. The GLOF will have devastating impacts on the infrastructure including homes, lands, schools, etc. The settlement along the river site could be adversely affected as a result of GLOF (**Figure 5**).

**Figure 4.** *Khurdopin Glacial Lake formation.*

**Figure 5.**

*Contribution of hazardous share in different glaciers along CPEC.*
