Attabad Landslide Disaster
Visual Observations and Estimations
Attabad Landslide Disaster Visual Observations and Estimations
Submitted to
FOCUS HUMANITARIAN ASSISTANCE PAKISTAN
BY EJAZ KARIM Geologist (Ex-Programme Officer FHAP)
Dated: January 4, 2010
First Draft Report
Attabad Landslide Disaster
Visual Observations and Estimations
Background
Attabad (Ghariat) is a remote village located (E74.80 , N 36.20) about 20 kilometers upstream of Aliabad, high up on west side of valley, just beyond the great mid-nineteenth century landslide dam (below salamanabad). This was a phenomenal event creating a blockage about 300meters high and with remnants still to be seen today, forming a significant topographic feature (by S. Jalal Ud Din shah, Ejaz karim and Hadi Husseini). The village was inhabited over a 15 meters thick (overburdened material Farooq & Ejaz) underlain by jointed granite rock outcrop. The overburden slope (Scree slope) is of colluvial nature comprising of sub-angular to subrounded boulders , cobbles and gravels with sand and silt matrix. The village was constituted with 80 houses, two middle schools, 1 AKES and Govt. middle school and 1 dispensary. Settlements were scattered towards eastern part while clustered towards western side. Construction types of the settlements was adobe type while some un engineered concrete type. Economically the villagers are poor. Village was accessible through an unpaved jeepable road linked with KKH (Karakuram High Way) Red line :Extent of slide through a suspension bridge over the Hunza River. Inhabitants were usually using unconsolidated patches of the scree slopes for agriculture making small terraces. According to the notables and other local population, in 1993 and 1996 long-lasting rains triggered intensive boulders fall along the slopes, affecting the land property with out any human loss. Just after rains and boulders fall, locals observed some displacement adjacent to contact between rocky slope and soft material and remained dormant till 2002. During the 2002 earthquake in Astore valley again activated the moving mass and local leadership intimated the FOCUS Pakistan Head Office Islamabad and a team of technical professional (FHAP Geologist) visited the site and developed monitoring mechanism and trained the local CERTs ( Cluster emergency response teams). However the probable impact was forecasted and intimated to relevant authorities and Institutions. (Ref. Reports: Preliminary field assessment of the Active Landslide at Attabad September 22, 2002 & Reconnaissance of Attabad village Landslide Hunza valley January 2007)
First Draft Report
Attabad Landslide Disaster
Visual Observations and Estimations
A regular and coordinated monitoring system by FOCUS, AKCSP and local community members was established. On January 2007 FOCUS head office Islamabad was again informed about the enhanced movement. Team of technical experts (Prof. Dr. Saeed farooq and Ejaz Karim Geologist) visited the site and thoroughly assessed the entire problematic area and declared for evacuation. Current Situation On January 4, (Monday at 11:30 AM), 2010, landslide incident occurred and whole river valley has been blocked. Information received till January 6, 17 dead bodies were recovered, 3 were injured and 550 population was directly affected while 1687 population displaced from three villages i.e. Ghariat, Ghmaey Sarat , Sarat). Similalry 20 to 30 bodies are still missing. 1 camp is also established in near by village Altit where 559 IDPs are registered. Needs Assessment FOCUS Pakistan has mobilized its DAR team (Disaster Assessment and Response Team). Their reports are awaited but from the short meeting with locals and responsible people of the response management committees, there is a need of food, winterized shelter, medicines and fuel. Upper Hunza i.e.Upper Hunza main valley, Shimshal valley and Chapursan valley are cut-off from the district headquarter Aliabad and 23000 population stuck due to KKH blockage. Prices of available daily use items are increasing rapidly. Health crisis seems an increasing challenge.
Valley Blockage (technical aspect)
Slide materials are comprised of huge rock boulder with dominant fine sand and silt matrix. The slip plan developed through a joint set dipping almost vertically toward the slope. The overburden pressure on the joint plans was exceeded gradually with passage of time. Before the slide there were partial plane failures along the front of the rock strata and openings were clearly visible with in the slope. The rapid downward moment of the bulk mass of displaced sediments into the gorge not only displaced the river bed material (marshy point bars) on either sides (up and down stream) but also created a tremendous thunder (air pressure) that caused the superficial destructions, while due to back bounce of the slide bulk mass from the front rock wall and splashed material of the river bed caused the burial of the houses settled at foot-hills down stream. Due to mixing of fine matrix fed by slide mass and silt deposits in river bed created a sludge and gushed 1.5 Km down stream while 700 meter upstream. Main front of the slide mass deposited on KKH (southern side).
First Draft Report
Attabad Landslide Disaster
Visual Observations and Estimations
The dimensions of the barrier are estimated below;
Total length of the barrier: 3000 m (Approx) Total length of main deposit: 1000m Total width of the barrier at apex: 550m (approx) Maximum height of the barrier at apex: 95 m (Approx) Minimum height of the barrier at apex: 85 m Volume of slide mass: 52250,000 m3
Profile of the barrier
1KM –Valley walls apart
KKH
(Approx) ☼☼At least two months are required to clear the road accesses.
Dimension of water Lake: (as recorded on January 4, 2010)
Length: 1Km Width: 180 m Depth: 25m Approx Volume of water in reservoir : 49,50,000 m3 Estimated peak flood discharge a 4 Km down stream: 6350 m3/sec Carrying capacity of river section at 4 Km down stream: 2700 m3/sec (during peak flow) Elevation of River bed at Multansa Spring): 2324 m Elevation at KKH on same spot: 2363m Height of KKH from river bed: 37 m Current upper water level of the lake from river bed: 29m (this thickness includes sludge and sediments with water) Rate of water level rise per hour: .6ft /hr (.19m/hr) Rate of water level rise per 24 hours: 14.5ft -(4 meters) Rate of water level rise in 7 days: 30 m
Important Note: The above calculations have been carried out on the basis of unit information provided by non professional field staff. The exact location of the reading point is not very much clear. However the other desired information has been extracted from Google Earth Satellite image and its interpretation. This data should not be used for site specific engineering measures. First Draft Report
Attabad Landslide Disaster
Visual Observations and Estimations
Potential Impacts and Protective Measures
• • In view of estimations there is potential threat for gradual inundation of Ayeenabad village. Early warning -first alert should be disseminated to susceptible population of the village Concentration should be on the clearance of the barrier. Prolong and late intervention may create following problem down stream; • Incase of late breach when water will strike the toe of slopes at Salman abad, it will trigger erosion at toe of the ancient landslide which is more susceptible resulting land sliding phenomenon which will create further damming issue on site. Similarly the reclaimed areas of flood plain with in the river section will be eroded inundated and cover with silt, sand and debris. According to estimated flow attenuation of the existing volume (till first week Jan); following locations are more at risk and need to intimate with early warning alerts well before time;
narrow valleys flow % 100.0 98.1 95.7 94.8 93.7 93.0 91.2 88.6 86.5 85.3 84.8 Locations Main blockage site Salmanabad Ahmed abad Faizabad Ganish Bridg Ganish flood plain Opposite Ghulkhan (Nager side) Faker(Nager side ) Miacher Minapin Pain Pissan (lower) Highly susceptible Highly susceptible Highly susceptible Highly susceptible Highly susceptible Highly susceptible Highly susceptible possible to activate the major landslide from opposite Along the stretch the river valley is narrow , due to toe cutting bank collapses can may happen Highly susceptible Remarks
•
• •
Distance from origin (barrier) 0 4 9 11 13.5 15 19 25 30 33 34
38 41 50 55 64 72 77 80 92 97
83.2 82.0 78.5 76.6 73.4 70.6 68.9 67.9 64.1 62.6
Ghulmet Thole and Hussainabad Khizerabad-Skanderabad Chalt Upstream Jaglot (ghur) along river Rahimabad Nomal Jotal Sultanabad Danyor
Highly susceptible
Highly susceptible Highly susceptible Highly susceptible Highly susceptible Highly susceptible
Above forecast is totally on estimated values, no field measurement and instrumentation data used
First Draft Report
Attabad Landslide Disaster
Visual Observations and Estimations
•
In case of late intervention in removal of the barrier, the impact on down stream low laying areas will be higher. Settled areas can be damaged due to bank collapse and slope failure.
•
As a lesson learnt there are three other main landslides indicated in below write-up need close monitoring through locals. Proper monitoring mechanism should be established in the following villages to avoid possible human and economical losses. In surrounding periphery of the problematic areas new habitation should be strictly discouraged.
First Draft Report
Attabad Landslide Disaster
Visual Observations and Estimations
Conclusion
Power crisis in country due to sacristy of water is common. Hunza River is one of the main tributary which is feeding to Indus River and ultimately accumulates in Terbela reservoir. Similarly Karakuram High Way (KKH) has its own strategic importance. Keeping in mind the current strategic situation of the country and requirement of the water for power generation are of prime importance. Similarly the population became isolated upstream due to road blockage have no alternate source for communication. Sorties by army and AKF Choppers can not meet the immediate and long term needs of the area. Early interventions for dame breach and road clearance not only benefit the population stuck upstream but also save the expected loss of lives and properties down stream. Rehabilitation of the victim in the same periphery of the site should strongly avoid and alternate safe site should be identified for future settlements.
Acknowledgement
Thanks to FOCUS Humanitarian Assistance Pakistan’s management and technical team members for providing support and making possible for aerial reconnaissance of the site. Author is always available for any kind of input related to disaster risk management.
First Draft Report