Three landslide-induced railway incidents in a single day

News today of three different incidents from around the world:
1. New Zealand
NZ Herald reports that a milk train hit a landslide in Manawatu Gorge.  Fortunately there were no injuries, or even a need to cry over spilt milk...



2. India
Bangalore Mirror reports that three coaches of the Thiruvananthapuram-Mangalore Express train were buried by a landslide in a narrow cutting at Mulunthurthy.  Three people were injured, plus there were some minor injuries during the evacuation.

3. Canada
Various Canadian newspapers report that there was a serious landslide-induced derailment of a freight train at St-Lazare in western Quebec.  The accident trapped the injured train crew in their cab, requiring that they were rescued by firefighters.  Heavy rainfall was reported to be the trigger.  The images of the site, from the Montreal Gazette, are impressive:

 

 Landslides represent  an important risk to railways in upland areas, and where extensive earthworks have been used.  Railway companies expend huge amounts of resource mitigating the threat, usually with success.  Incidents are quite rare, but previous examples described on this site include:
May 2010: 19 killed when a train struck a landslide in China;
April 2010: Nine people killed when a train was struck by a landslide in northern Italy;
July 2009: Four people killed when a train struck a landslide from a cutting in China;
Dec 2008: A train was struck by a flowslide formed from power station ash in Tennessee, USA;

Updates for Pakistan, China and India flood and landslide crises, 10th August

As yesterday, this is a brief review of the state of play with the three substantial landslide and flood crises in Asia.

1. Pakistan
The flood wave continues to work its way down the Indus, and is now in the Province of Sindh.   As forecast, heavy rainfall exacerbated the situation yesterday, with totals of over 100 mm in some areas of the province. Kyber-Pakhtunkhwa also saw falls of 30 mm or more in some areas.  Whilst not enough to cause the sort of devastation that we have seen of late, this is sufficient to keep river levels topped up.

 Working our way down the Indus, the second flood at Besham has now peaked and the hydrograph is showing a rapid decline. 

The peak flow in this econd flood was lower than in the first , but was still substantial.  This water will of course have to work its way down the Indus over the next ten days.  It will be interesting to see how this flood looks when it reaches Taunsa.

Moving down to Guddu, the peak discharge appears finally to have passed, meaning that water levels will be slowly falling.  Note however that if the flow behaviour at Taunsa is a guide, the rate at which the water levels fall will be quite slow, meaning that the people have several more days before they will be able to start rebuilding their lives.  Note also that the flood level is still above the exceptionally high level.  The flat peak component of the flood record causes me to reiterate my suggestion yesterday that the hydrograph shown below has not accurately captured the peak flow:

Going south again, and the main concern is now at Sukkur, where the hydrograph appears to be suffering the same problems of saturation at the peak:

Some media reports have suggested that the peak flow here is actually 1.2 million cubic feet per second.  The media are also reporting concerns about the safety of the Sukkur barrage, with several reports suggesting that deliberate breaches of levees are being considered to try to reduce the peak flow.  It seems that a similar exercise was undertaken upstream at Ghouspur, with the inevitable destruction that followed.  However, it is important to understand that these barrages provide irrigation for vast areas of productive agricultural land that is vital for the sustenance of the population of Pakistan.  Deciding on how to protect them is not an easy task.

However, as at Attabad the apparently poor communications strategy of the authorities is unfortunate.  Whilst putting the hydrographs online is a good step, it would be sensible to accompany this with a decent explanation of what is happening, where the threats lie, and the action that might be needed to mitigate them.  Whilst this would not prevent the destruction, at least people might understand why particular courses of action are being followed.

Finally, for northern Pakistan the Pamir Times has provided two updates in the last 24 hours on the Attabad situation.  Most importantly, the water level is now falling, having apparently risen by 6 feet (about 1.8 metres) at the peak of the floods, which caused further widespread destruction. Meanwhile, they continue to note that other landslides have caused severe hardship, and that the Hunza was blocked at Rahimabad to the north of Gilgit.  As far as I can tell Rahimabad is in the valley shown in the Google Earth image below:

Meanwhile, the Pamir Times has also provided some new images of the state of the Attabad barrier itself:

These appear to indicate little change in the state of the dam over the last couple of weeks.  Operations to lower the spillway level have yet to start, but it is heartening to see in some of the images that a monitoring team appears to still be on the site.

2. China
Rescue operations continue at the Zhouqu landslide site, where the number of known fatalities is now 337.  The reported number of missing people is 1,148.  There can be little chance of recovering many further survivors, although one victim was recovered alive today.  The state media are reporting some tales of real anguish in the aftermath of the disaster, exacerbated of course by the "one child" policy in China.  The government is attributing the disaster to the normal villains - poor geological conditions, the recent drought, the heavy rainfall, and the aftermath of the 2008 earthquake.  This is all likely to be true to at least some degree, but there may be other factors as well, most notably deforestation and the legacy of mining activities.  The internet age has spawned a wave of amateur investigative journalism in China.  This All Voices page reviews recent postings of Chinese documents about the landslide hazard in Zhouqu.  Whilst I am naturally sceptical of some of this material, it does appear that the risks to communities posed by landslides in these mountains is well-documented.  In particular, this newspaper article, from 2008, identifies that the slope problems at Zhouqu are sufficiently serious that they have been the location of various studies by Japanese landslide scientists.  However, to be fair to the government, the range of landslide problems in the aftermath of the 2008 earthquake is so serious that prioritising and finding resource to mitigate appropriately is impossible.  Expect more landslide disasters in central China in the coming years.

Two images have appeared in the last 24 hours that demonstrate the magnitude of this slide.  This AP image shows the landslide from the opposite bank:

I would really like to see the source of this huge debris flow - has anyone seen an aerial image of the upper reaches of the track as yet?

And this AP image illustrates the likely velocity of the movement, given away by the mud deposit on, and indeed in, the upper part of the building:

Finally, unfortunately tropical storm Dianmu is moving northwards off the east coast of China.  Although it is unlikely to landfall in China itself, expect heavy rainfall across eastern and central China.  Given the intensity and magnitude of the recent rainfall, this is potentially deeply problematic.

3. The Ladakh debris flows in India
The forgotten disaster amongst everything else that is going on is the Ladakh debris flows that occurred on Friday.  To date the number of known victims is reported to be 165 people, with a further 500 thought to be missing (with very little chance of survival now).  However, Save the Children is reported to believe that the true toll is likely to be in excess of 1,000 because several affected villages have yet to be accessed.  Localised heavy rainfall continues in the area, disrupting relief operations and causing further damage.

One of the most seriously affected towns was Choglamsar.  This is the settlement in the foreground of the perspective Google Earth image below - the presence of the huge debris fan in the background is a clear sign of the processes that have allows the formation of the comparatively flat areas upon which the town is built:

Protecting the town against repeats of this event is not going to be an easy task, but debris flows must be expected on a fan such as this.

I will try to provide further updates tomorrow morning, or sooner if events require.

Updates on landslides and floods in Pakistan, China and India

It is rather difficult to keep up with all the landslides occurring in Asia at present, so for now I'll provide a brief review of the current situation across the three major areas affected:

1. Pakistan
The situation in Pakistan becomes increasingly desperate.  Further heavy rainfall in the mountains in the northwest has meant increased landslide and flood occurrence, and a huge reduction in the aid effort.  The FFD hydrographs in the mountain areas are steadily rising again.  For example, this hydrograph is for Skardu shows that flow is greater now than it was in the heavy rainfall of ten days ago:

Downstream at Besham (close to the mountain front) the discharge is not as high as it was in the first set of floods, but it is rising and the level is undoubtedly high:

The area under the curve is the total volume of water that has been involved in the flood.  This suggests that in terms of overall volume this flood is larger than that of the events last week, even though the peak flow is (so far) lower.

Downstream at Sukkur and Guddu the flow remains exceptionally high.  At Guddu the hydrograph suggests that the peak flow has now been maintained for over 24 hours.  This looks odd - I wonder whether the discharge has exceeded the capacity of the measurement system. 

However, according to the FFD a larger discharge has been measured at Guddu before - in 1986 a discharge of 1,200,000 cusecs (cubic feet per second) was measured at this point.

At Sukkur the discharge is continuing to rise, and based upon the Guddu hydrograph may have some time to go before the peak is reached.  The maximum recorded flood at this point is 1,170,000 cusecs in 1986.

GEO News is reporting that the city of Muzaffargarh is now being evacuated.  Given that this is a city of 165,000 people, the severity of the situation is clear.

2. China
Xinhua continues to provide full coverage of the desperate attempts to save people trapped by the landslide in Zhouqu, Gansu Province yesterday.   The magnitude of the slide is clear from the story of the survivor rescued this morning - she was recovered from a an apartment that had been inundated by debris.  The rescuers had to break through a wall to reach her - even though her apartment was on the fourth floor of the building.  Meanwhile the landslide dam has been successfully breached, which at least deals with one key issue.

3. India
The debris flow at Ladakh is now known to have killed 132 people, but a further 500 people are reported to be missing.  The level of damage is really very high indeed, as this AP image shows:

A fascinating insight into the process that occurred at Leh is provided by this commentary from geologist Ritesh Arya, who was in the head scar area when the failures developed:

"Speaking to TOI on phone from Leh, Arya, who was sleeping in a house in Choglamsar village when the entire area abruptly began to move, said: "This village is 6km from Leh on a hillock formed by mud itself. I woke up when I felt massive vibrations and found that the whole hill-side was moving." The loose soil had softened further due to torrential rains. "This is a rare geological phenomenon, and though landslides are common, mud creeps like this are unheard of," said Arya, who holds a Guinness Book of World Record for discovering ground water at an altitude of 11,000 ft in Ladakh.

Describing the sheer size of the mudslide, Arya said: "Its dimensions make it so scary: it was about 20meter high and several kilometers wide." All the houses coming in its way appeared to just dissolve into it as it roared on, destroying the Leh bus stand and the BSNL exchange, said Arya. The mudslide is believed to have travelled 6km, bulldozing the Choglamsar village. Arya said most roads have disappeared under the debris. The worst-hit are the heritage buildings and old houses, traditionally made of mud.

"'People were completely caught unawares. Then suddenly, everyone started scrambling as the enormous amount of loose mud and debris was unleashed. Those who survived in the Choglamsar village had to waded through five-ft high mudflow," said Arya. "There are bodies still buried in the debris and I found arms and legs sticking out at several places," he said."

Whilst elements of this are over-hyped (for example this is far from "unprecedented"), the observations are very helpful and interesting.

Debris flow disaster in Leh, Indian Kashmir

Thanks to several people for the heads up on this.  Various Indian news agencies are reporting that the town of Leh in Ladakh, Indian controlled Kashmir was hit by a series of debris flows / flas floods triggered by a cloudburst.  The reported death toll is currently reported to be at least 50, and may increase substantially.

This Panoramio image gives a fairly good idea of what Leh is like:

New rockfall video from India

A good new rockfall video has been posted on Youtube, collected in the Pangi Valley of Himachal Pradesh in India:

Presentation of lanslides caused by Tropical Cyclone Aila in Darjeeling

The Savethehills blog has an interesting presentation on their website focusing on the landslides caused by Tropical Cyclone Aila in Northern India in May this year. It can be accessed here:

http://savethehills.blogspot.com/2009/12/cyclone-aila-in-photographs.html

A surprising spell of landslides

In most years in which I have been collecting landslide fatality statistics (since 2002) November has been a month with quite low landslide occurrence. Not this year though - in fact the last few days have been more like the summer monsoon season, with fatal landslides occurring in a wide range of places. Examples include:

• El Salvador on 6th November, in which the volcanic lahars triggered by Hurricane Ida appear to have killed over 100 people, with a few (very speculative) reports of rather more;
• South Sulawesi in Indonesia, when 13 people were killed in a slide Palopo;
• Tamil Nadu on 9th and 10th November, when a number of landslides killed at least 30 people;
• Casamicciola on Ischia in Italy on 9th November, when a 15 year old girl was killed by a slide that carried her out to sea in a bus;
• Bukittinggi in West Sumatra on 10th November, when two people were killed;
• Wassa-Akropong in Ghana on 10th November, when up to 30 people were killed in a landslide in an illegal mine;
• Goha village in Tanzania on 10th November, when 20 people were killed in a landslide.

In addition there have been reports of non-fatal landslides in the USA, Serbia, Vietnam, etc. I cannot tell at the moment whether this is just coincidence or something more significant, perhaps due to the El Nino conditions. With Cyclone Phyan currently bringing heavy rainfall to central western India, an area that is landslide-prone, there could be further events in the next few days.

Reported landslide accident in SW India

AP is reporting that a landslide in S India has killed 39 people. The landslide occurred in the Ooty and Coonoor region of Tamil Nadu states, hitting 300 mud huts. The report quotes a "state flood control official" as saying that 14 bodies were recovered on Monday and a further 25 today.

Tamil Nadu is in the very south of India. The TRMM landslide warning system has this region as being likely or very likely to suffer landslides:

Landslide round-up: Philippines, India and Italy

1. Philippines
Typhoon Parma (known as Pepeng in the Philippines) has churned its way across the northern part of Luzon in the Philippines. Fortunately, its track took it north of the most vulnerable area, which is the first bit of good news for a while:


However, early reports are that the storm has triggered some landslides:

"Rains in Benguet province set off landslides in which at least 12 people were killed, police said. The victims included seven small-scale miners who were sleeping in a shelter when they were buried by one landslide, said provincial police chief Loreto Espeneli."

And this from GMA News in the Philippines:

"At least 12 people were killed in two landslides that hit their homes in Benguet province in" the wake of typhoon “Pepeng" (Parma), a radio report said Sunday. Radio dzBB’s Benjie Liwanag Jr. reported that seven people, including a family and two guests, were killed in a landslide in Sitio Manganese in Ampukao village in Itogon town. The incident occurred at about 2 a.m., the report said. The fatalities were not immediately named, but the report said the two guests were from Ifugao province."

"On the other hand, dzBB said five members of a family were buried in their house at Beckel village in La Trinidad town Saturday night. Their bodies were recovered Sunday morning."

2. India
The very heavy rain in southern India is continuing to cause major problems. On Friday it has been reported that a landslide struck Kadwad in Uttara Kannada district in North Karnataka:

"In Kadwad village, a landslide occurred in the Madibag area on Friday afternoon, where 24 people were buried alive when the nine houses collapsed. While a minor landslide had already occurred later, the people residing between the railway track and the hillock area of the village did not expect another landslide. But, by evening boulders and mud from the hill began rolling down and seven families bore the brunt of this negligence." (note I suspect that the use of the term "negligence" here may be a mistranslation"

3. Italy
The Italian news agency ANSA is now reporting that the loss of life in the mudslides in Messina at the end of last week is 22, but that this is likely to continue to rise. There appears to be growing anger about the links between this disaster and illegal construction.

Typhoon Parma update, plus landslides in Indonesia, India, Sicily, Samoa, Cambodia and Vietnam

I am struggling to keep up with the natural disasters at the moment. The main point of this post is to highlight the continued threat of Typhoon Parma to the northern Philippines. The current track forecast has it making landfall in the next day or so in the northern part of Luzon. The forecasts are still that it will stall as it makes its way across that area - this is typically the scenario that leads to very heavy rainfall and hence many landslides. Note also that at the moment it is not clear where it will go once it clears the Philippines, but the South China Sea is warm, which could lead to a re-intensification:

Meanwhile the last week has been grim for landslides:

1. The Samoa earthquake and tsunami has received some publicity, but has been overshadowed by events elsewhere. The intensity of the shaking may well have triggered some landslides, and of course there is the possibility that a submarine slide contributed to the tsunami;
2. The Indonesian Earthquakes: there are lots of reports of landslides triggered by the earthquakes. These slides appear to have cost lives directly and also to be hampering the rescue operations due to blocked roads.

3. Typhoon Ketsana: Cambodia and Vietnam were both hit very hard by typhoon Ketsana. Reported death tolls are 99 people in Vietnam and 14 people in Cambodia, adding to the reported 293 fatalities in the Philippines. In each case landslides appear to have been a major factor.

4. Rain in India: 140 people are reported to have been killed in heavy rainfall in the states of Karnataka, Andhra Pradesh and Maharashtra. At least some of these are the result of landslides - for example, a single landslide killed eight people in Maharashtra yesterday.

5. Mudslides in Sicily: heavy rainfall in Sicily last night triggered extensive mudslides around Messina killed at least 14 people. Image below from here (not my normal daily read I should quickly add):

I cannot remember a time with so many events occurring simultaneously. Certainly an interesting time as the old curse says.

A bad summer for landslides in Darjeeling District, India

Regular readers will know that I occasionally highlight the great work being undertaken by a small group of concerned citizens, Save the Hills, to raise awareness of landslides in Darjeeling District in northern India. This work is profiled in a blog, Visions of Hell, run by Praful Rao. As this is an area affected by the SW Monsoon, the summer is the main landslide season in this region. Although the vearly part of the monsoon this year was quite weak, August has seen heavy rain and many landslides. In particular, on both 15th August the area had about 60 mm of rainfall, followed by a further 190 mm on 19th August. The results were all too predictable, with multiple landslides. Strangely though these incidents have been scarecely reported even by the media within India, or in the daily reports of the National Disaster Management Division there.

Praful Rao has written an illustrated report of the latest destruction caused by the landslides, available here.

A dreadful weekend of landslides

The last few days have been a dreadful period for landslides. I really cannot cover all that has happened in enough detail, so all I can do is to outline the main events:

1. Rotorua rockfall, New Zealand
Actually the period started with a very lucky escape in New Zealand on Thursday when a rockfall on a slope under maintenance crushed a car with two passengers. Both were trapped but were extracted from the car with minimal injuries. Given the size of the blocks and the state of the car this is pretty remarkable image from here:



2. Shunhe township, Hanyuan county, Sichuan province, China
The large valley-blocking landslide in Hanyuan County also occurred on Thursday. This slide, which is reported here, is believed to have killed 31 people. The partial blockage of the river continues to cause problems:

3. Mount Pinatubo, Philippines
On Friday the Philippines was hit with very intense rainfall that appears to be from the outer edges of Typhoon Marakot, which hit Taiwan and then China. There were two disastrous landslides - in the first a lahar hit a tour group and their guides on the flanks of Mount Pinatubo, killing two locals and three tourists.

4. Kias, Baguio, Philippines
In the second incident, also on Friday, a landslide hit a group of miners at Kias, near to Baguio in the Philippines. A group who went to their rescue were then hit by a second landslide, killing 14 people in total.

5. Pithoragarh district, Uttarakhand
On Saturday a large landslide occurred in northern India (see image below from here). The true impact of this is a little unclear, but the current estimate of loss of life appears to be 43 people. Thanks to David Hopkins for the heads-up on this one, and to Sekhar for the photo).

6. Typhoon Marakot, Taiwan
The true impact of Typhoon Marakot is far from clear, with reports of debris flows that might have killed hundreds. It is important to stress that these are unconfirmed, but with 2.4 m of rainfall in a weekend who knows? A slightly clearer report suggests that Taoyuan Village in the county of Kaohsiung was hit by a debris flow that killed 16. We will wait for the morning to see whether the reports of much higher loss of life are correct.

The low level of NH hurricanes and typhoons in summer 2009

One of the reasons that the northern hemisphere summer is essentially the global landslide season is that landfalling tropical cyclones (typhoons and hurricanes) represent a rather efficient way of triggering slope failures. This is especially the case in the Caribbean, Taiwan, Japan, SE and S China, the Philippines and Vietnam. Typhoon rain is astonishing to experience for the first time - peak intensities of 100 mm per hour are not unusual in the largest events. The hourly rainfall data below is for the passage across Korea of Typhoon Rusa in 2002, taken from Lee and Choi (2007):

Note that at Gangneung the peak hourly precipitation was 100.5 mm (4 inches) and the peak 24 hour rainfall was 870.5 mm (35 inches). It is unsurprising that such events cause landslides on a large-scale.

The northern hemisphere tropical cyclone season is primarily associated with warm sea surface temperatures, and hence runs primarily through the summer and early autumn months. Interestingly, and for reasons that are far from clear, the energy associated with northern hemisphere tropical cyclones has been reducing for a number of years. Ryan Maue at Florida State University runs a superb web page that tracks tropical cyclone occurrence globally. He has the following graph of global and northern hemisphere tropical cyclone energy (note smoothed using 24 month running sums):

Levels of tropical cyclone activity are now approaching a 50 year low. However, even by recent standards the level of Northern Hemisphere tropical cyclone activity to date this season has been exceptionally low. Ryan also provides the following graph of Northern Hemisphere tropical cyclone energy (ACE) for the first three months of each season since 1979:

It is not for me to speculate on why tropical cyclone activity should be at such a low level (Ryan is much better qualified to do so), but it is clear that so far the Northern Hemisphere tropical cyclone occurrence has been a damp squib. The occurrence of landslides reflects this (I will post my monthly update in the next few days). This is of course good news in terms of landslides and floods, but it is bad news for farmers who rely on rainfall for irrigation, the hydro-electric industry in these areas, and many others whose livelihood and.or welfare depends upon water derived from tropical cyclones.

It will be interesting to see whether level of activity dramatically increase later in the season.

Meanwhile, the S. Asian monsoon remains very weak, with the Indian Meteorological Department noting that total precipitation in the monsoon season is 19% below the long term average. Again, the occurrence of fatal landslides that I have recorded is mirroring this pattern. Meanwhile, much of China is suffering from unusually intense monsoon rains. For example, Shanghai has just suffered its heaviest rainfall for 70 years.

Update on the South Asian Monsoon

The seasonal landslide pattern in South Asia remains very substantively below the long term mean this year - to date at least the monsoon is failing. The level of the problem is illustrated rather well by this map of the monsoon season rainfall anomaly for India, from Monsoon Online:

The result is that the number of landslides in South Asia is very much below average, which is of course good news.

It is interesting to compare this year with 1997. This is part of a press release from 26th June 1997, put out by the Indian Institute of Tropical Meteorology:
"Unfavourable conditions trigger worry over south-west monsoon (26 June 1997)
Weather experts at the India Meteorological Department are keeping their fingers crossed over the performance of the south- west monsoon, as the waters of the Pacific Ocean are getting warmer. Warming of the Pacific is of significance since it means that there is no hope, at least for the time being, for the El Nino factor, which has a important influence on the monsoon, to become favourable. On the contrary, it only meant that it could have a more adverse impact than what was envisaged a month ago. To add to the problem, the Southern Oscillation, which is another global climatological phenomena that influences the monsoon, has also become more unfavourable. While El Nino is a reflection of the warming of some regions in the tropical Pacific Ocean, Southern Oscillation is an index of difference of pressure between the Pacific Ocean and the Indian Ocean. El Nino is considered favourable if the temperatures in the Pacific Ocean, particularly off the coast of Peru are low, and Southern Oscillation is considered to be advantageous if the atmosphere pressure in the Pacific Ocean is less than that in the Indian Ocean. The officials have, however, not given up hope on the ground that there was still a long way to go before the monsoon, which is active for four months, comes to an end in September. "

Interestingly the monsoon was 8-10 days late across most of the country that year. In the end the monsoon rainfall total was slightly above average, but characterised by very heavy rainfall, which caused floods and landslides, in late August.

1997 was of course the start of the largest El Nino in the last 60 years. It is unsurprising that the monsoon is currently showing a similar pattern as a new El Nino develops. The landslide pattern is apparently reflecting this.

The National Centre for Landslide Research, Studies and Management in India

Yesterday, the Indian National Disaster Management Authority held a press conference to announce the publication of a new set of "National Disaster Management Guidelines – Management of Landslides and Snow Avalanches". At this press conference it was also announced that the Indian Government will set up a National Centre for Landslide Research, Studies and Management, to be located in one of the most landslide-prone states (I would guess that this will either be in the north of the country or in the south-east). Unfortunately at the moment there is little information available about this centre, other than what was contained in the speech given by the Union Minister of Mines and DONER, Shri Bijoy Krishna Handique:

"The proposal for establishing a National Centre for landslides research, studies and management, as recommended by the guidelines is a welcome step in the direction of capacity building and research and development and I feel that GSI [Geological Survey of India] will be able to host this Centre as part of its core activities. Such a centre of excellence will ensure adequate national coverage, information flow, community participation, networking, and feedback with regard to landslides and snow avalanches, besides coordinating the effort of the states and other concerned central organizations. It will also foster, promote, and sustain a scientific culture in the management of slopes and landslides and encourage the transition to a culture of prevention, mitigation, preparedness and response."

Given that India has a pretty serious landslide problem that appears to be getting worse, this is a very sensible move.

I would like to get hold of a copy of the guidelines, but at the moment they are not available. However, the press conference suggested that they cover nine distinct areas:

• Landslide hazard, vulnerability, and risk assessment
• Multi-hazard conceptualisation
• Landslide remediation practice
• Research and development
• Monitoring and early warning of landslides
• Knowledge network and management
  
• Capacity building and training
• Public awareness and education
• Emergency preparedness and response
  
• Regulation and enforcement.

All of which sounds very sensible!

Landslides and the Kailash Mansarovar yatra

One of the great pilgrimages of the Hindu faith is the Kailash Mansarovar Yatra, which is a 400 km trek up to Lake Mansarovar in Tibet. This pilgrimage is very demanding - the lake is at 4550 m above sea level. It is undertaken in groups of 60 people over 26 days. Each year the first group sets off on 1st June.

The route is shown below (from here):


This year the pilgrimage is going to have an additional challenge. I posted back in February about the Chautuldhar landslide in northern India, which was causing major problems in the close area of Tawaghat in Dharchula. The landslide is not quite where I thought it was back then - it now looks as if it is on the section of slope shown on the Google Earth perspective view below:


A close look at the map above will show that Tawaghat is right on the route of the pilgrimage. Unfortunately, the landslide remains active - indeed David Hopkins has been kind enough to send a translation of an article in a local paper for this area, dated 27th May:

"During the past sixty hours rocks and stones have been showering down from the mountain in Chautuldhar. Following the recent rains the mountain in Chautuldhar is on the move again. The temporary road made across the slide has been swallowed up by the river below. People are taking their lives into their hands to cross the slide. With two bulldozers of the BRO (Border Roads Organisation) stuck on the Tawaghat side problems have only increased. From Friday to Sunday following very heavy rains, rocks and boulders are continually raining down from the mountain."

To deal with this problem a diversion has been created, but this is reported to be "treacherous" and likely to add two days to the length of the trek.

Landslides from Cyclone Alia in Darjeeling

One of the most admirable landslide websites that I know is the Save the Hills blog, which is the mouthpiece of a community level group trying to raise awareness of the problems of landslides in Darjeeling in NE India. I have featured this site several times before.

As Cyclone Alia has closed in on the area over the last few days See below) they have been warning of the danger of landslides triggered by the rainfall that the cyclone would inevitably bring. The Cyclone passed across the area yesterday - and sure enough reports are now emerging of the landslides that the rainfall has triggered. At the time of writing Sify is reporting 22 killed in landslides, with 10 injured and another six people reported missing. Over 100 landslides have been reported. The Times of India reports that 245 mm of rainfall fell in a 24 hour period.

Meanwhile, in the last few days there are also reports of a large landslide in Sialum District in Morobe province of Papua New Guinea, which is reported to have killed 19 people (although the picture is still rather unclear), landslides in Bhutan with at least one fatality, mudslides in Uttar Pradesh in India that killed eight people, and landslides in Guangdong that have killed four. Finally, there are some very unclear reports about the magnitude of the impact of heavy rainfall in Afghanistan, with reports of about 95 people killed in landslides and floods.

Sadly, none of this is particularly unusual as we are seeing the impacts of the development of the summer monsoon across Asia.

The Pareechu landslide and flood, 2005

In July 2003 a landslide occurred on the Pareechu stream at 32.322N, 78.735E, a remote tributary of the Satluj River in Tibet (see Fig. 1). The landslide was quite large, blocking the river and allowing a lake to form that eventually breached. In this post I will try to use the range of satellite imagery and reports that are now available to describe the sequence of events.

Fig. 1: Google Earth location map of the Pareechu landslide (click on the image for a better view in a new window)

NASA produced an ASTER image of the site that was collected in October 2003, before the landslide occurred (Fig. 2). This shows the rather strange landform at this site - i.e. a broadening of the river in which there has clearly been extensive sedimentation.

Fig. 2: NASA ASTER image of the Pareechu landslide site before failure

It is not clear what triggered the landslide, but another ASTER image collected in July 2004 very clearly shows the immediate aftermath of the slide (Fig. 3).

Fig. 3: NASA ASTER image of the Pareechu landslide site after failure

Note that the basin is now being filled by a lake. The landslide itself is not particularly clear, although the extensive dust kicked up by the slide is fairly obvious as a whitish colour mantling the slopes just to the east of the lake. It is certainly clear that the valley is blocked. An enlargement of this area helps a little (Fig. 4).

Fig. 4: Enlargement of the NASA ASTER image of the Pareechu landslide site after failure

There is an image available in the following presentation (slide 7) that provides a view of the site in August 2004 (Fig 5):
http://www.managingclimaterisk.org/document/SAARC.pdf

Fig. 5: Presentation image of the Pareechu landslide site after failure

The landslide is clearer here, but note also that there is water flow clearly evident, so presumably at this point the landslide had overtopped the barrier. Note also though that the lake is still present, so presumably the flow was not large enough to induce significant erosion.

The next available image is from 20th February 2005 (Fig. 6). Of course this is the middle of winter, so unsurprisingly everything is frozen up. Nonetheless the lake is clearly still present.

Fig. 6: Google Earth image of the Pareechu landslide site in February 2005. The site is of course mantled with snow.

It does appear that there is some flow in the river, but not over the dam, presumably indicating that some seepage was occurring. This high resolution image also gives the first opportunity to get a good look at the slide, especially when the Google Earth terrain model perspective view is used (Fig. 7).

Fig. 7: Perspective Google Earth image of the Pareechu landslide site in February 2005.

It is clear that the landslide here was actually a comparatively small failure of a much larger rock slope failure. However, in turn this active section is part of a much larger rock slope failure that is delineated by a large fracture running across the hillside. I have highlighted this on Fig. 8.

Fig. 8: Annotated Google Earth image of the Pareechu landslide site in February 2005.

At its maximum the lake was 2,100 m long, 1,100 m wide and about 40 m deep storing about 64 million cubic metres of water, according to Gupta and Sah (2008). The dam appears to have failed at about 11 am on 26th June 2005, releasing a flood wave down the river that had a maximum measured discharge of about 2000 cubic metres per second. Fortunately, according to Gupta and Soh (2008) no lives were lost, although press reports at the time indicated that a small number of bodies were washed into India from Tibet. In India the flood did wash away 8 bridges, 15 km of road and caused damage estimated at US$177 million. It is not clear how much damage was caused in Tibet.

The final image, also from Google Earth and dated 4th September 2006, shows the site after the dam breach (Fig. 9).

Fig. 9: The most recent (Sept 2006) Google Earth image of the Pareechu landslide site

Note that the dam is still holding back a little water, but that this volume is now quite low. However, the slope above still looks highly unstable, so a repeat looks inevitable in due course.

Reference
Gupta, V. and Sah, M.P. 2008. Impact of the Trans-Himalayan Landslide Lake Outburst Flood (LLOF) in the Satluj catchment, Himachal Pradesh, India. Natural Hazards, 45, 379-90.

Early May is the start of the landslide season

Whilst the transition towards the Northern Hemisphere summer is rather pleasant for many of us, the start of May also marks the start of the landslide season in the Northern Hemisphere. Of course the main problems kick in when the SW monsoon really gets going in Asia and the tropical cyclone season properly begins in the N. Pacific and N. Atlantic basins, but already there are clear signs that the land is starting to move. Overnight, a number of Pakistani news agencies have reported a large landslide in the Neelam Valley:

"At least 28 people were trampled to death due to landslide in Neelam Valley on Tuesday, Geo news reported. According to sources 28 people have been trapped under the landslide in Jora area here in Neelam Valley, part of Azad Jammu and Kashmir (AJK). The rescue activities have been kicked off after the tragic incident and the trapped dead bodies of the unfortunates are being dug out, sources added."

Of course the Neelam Valley was pretty badly affected by the 2005 earthquake (the image below shows a part of the valley in 2006), so ongoing landslide problems here are not a surprise.


Meanwhile, the Philippines has already been battered by one typhoon (named Kajira in the Pacific-wide system, or Dante in the Philippines), which triggered a landslide in Sorsogan that killed 23 people. Unfortunately, there is another one (Chan-Hom) en route for northern Philippines at the moment (Tropical Storm Risk):


The good news is that Tropical Storm Risk (see long term forecast here) are forecasting a below average season for typhoons (activity is anticipated to be 20% below the long term mean). The long term forecast for the monsoon in India is essentially average (forecast rainfall = 96% +/-5% of long term mean.

Landslide on the Mahakali River on the Nepal / India border

Thanks to both David Hopkins and Ripendra for drawing my attention to a landslide on Friday on the Mahakali River on the border between Nepal and India. Although it has occurred in a remote area, it is interesting because the landslide appears to have partially blocked a fairly large river coming down from the high Himalayas.

The landslide occurred in the Chautuldhar (Chetalkot) area of Rephalikot, close to Tawaghat in Dharchula, right on the border of Nepal (to the east) and India (to the west) (see Google Earth image below - click on the image for a better view).

The reports suggest that cracks were first seen on Thursday, which led to a large scale failure on Friday. The location is shown on the Google Earth perspective view below (the actual location of the landslide appears to be in a small area of low resolution imagery):


Reports suggest that the river is flowing through a gap of just 2.5 metres, which has created a barrier lake that is threatening a number of villages upstream. The main road is blocked and may take as much as a month to reopen, and there is a threat of further landslides.

An interesting dimension to this is the proximity of the Dhualiganga I hydroelectic scheme. I have annotated the diagram above to show the location of the dam and the power house. This is a run of the river scheme in which the Dhauliganga River has been dammed with a 56 m high concrete faced rock fill dam to create a head of water. The water is then passed through a tunnel beneath the mountain to the powerhouse, where turbines are located. The project was completed in October 2005. Some newspapers are speculating that the landslides may have been associated with the construction of the tunnels as the failure occurred in the dry season with no obvious trigger. However, the tunnel is 6 km from the landslide site, so this is not likely. However, if a large lake were to form at the landslide site, and then was to be released rapidly, then the powerhouse would be threatened. It is not clear to me whether this is a possibility, but given that the river is now reportedly flowing again I suspect the chances at present are low.

As an aside, the dam site itself appears to be quite interesting from a slopes perspective: