24 September 2014

Sunkoshi landslide – reopening the road

Sunkoshi landslide

A couple of weeks ago, and with great fanfare, it was announced that the diversion roads around the Sunkoshi landslide were now open and the traffic was flowing again on the Arniko Highway, linking Kathmandu with Tibet.  The timing was important as this is a key route for the flow of goods into Nepal, and there was real anxiety about the effects of having large numbers of container lorries stuck to the north of the border.  From the very start I was concerned that these roads would be very vulnerable to landslides in heavy rainfall.  In the last few days news about the flow of goods has gone very quiet, coinciding with a period of heavy rainfall.  The obvious implications were that the roads were blocked once more, but there was little hard evidence.

In the last few days geotechnical engineer Giorgio Maderni travelled along the highway.  He has very kindly sent the following images to me (note that he retains copyright).  The first shows the old Arniko Highway upstream of the dam.  The level of the water prior to the breach is clear, as is the damage that the road has suffered:

Sunkoshi landslide

Copyright: Giorgio Maderni

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Further downstream the level of damage to the road and infrastructure, and the slow progress in putting it right, is clear:

Sunkoshi landslide

Copyright Giorgio Maderni

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The size of the breach of the landslide dam is impressive:

Sunkoshi landslide

Copyright Giorgio Maderni

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The very poor state of the track across the landslide debris is clear from this image.  In the distance a long queue of trucks waiting to cross the landslide can be seen.

Sunkoshi landslide

Copyright Giorgio Maderni

 

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And this image shows the state of the road in more detail.  It will be a difficult task to get this to a state in which it is possible to see two-way movement of large numbers of trucks:

Sunkoshi landslide

Copyright Giorgio Maderni

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At present there is no news about the alternative roads, but given that the trucks are queued up the assumption must be that these are also in a poor state,

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23 September 2014

Joshua Tree mudslide, California – a very lucky escape for a baby

Joshua Tree mudslide

Last week a mudslide, triggered by heavy rainfall, swept through Joshua Tree in California.    This video shows an event on the same day at Joshua Tree, though I’m not sure if it is the same event:

The mudslide swept through the small town, and killed one person who, according to the reports, attempted to drive across the channel before becoming stuck.  The mudslide struck his car, killing him.  In the town, the mudslide struck the house of the Scarcy family, sweeping through the building.  Breitbart has an image of the aftermath, showing how the mudslide demolished the rear wall of the building:

Joshua Tree

Breitbart: http://www.z1077fm.com/storms-cause-a-fatality-in-joshua-tree-mud-and-flooding/

In the bedroom at the back of the house, one year old Tristan Scarcy was asleep when the mudslide struck the house.  By the time his parents were able to get into the room he had been washed away.  The likelihood of anyone, let alone an infant, surviving being caught up in a mudslide is very low, Tristan was found alive about 60 m downstream of the house.  He had some cuts and bruises, and some debris in his lungs, but he’ll make a full recovery.

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19 September 2014

Moving to the University of East Anglia and two new landslide videos

Moving to the University of East Anglia

Regular readers will have noted my lack of blog posts in recent weeks, for which I apologise.  As you may be aware I have been changing jobs – I gave up the Wilson Chair in Hazard and Risk at Durham University last Friday, and on Monday took up the position of Pro-Vice-Chancellor (Research and Enterprise) at the University of East Anglia.  The last week has been a whirl of introductory meetings, all of which have been great fun.  This hasn’t left much time for the blog, but as I now feel established I will be returning to previous levels of activity.

So to get things underway again, two new landslide videos have appeared on Youtube in the last week:

A lucky escape in Costa Rica

In the last few days very heavy rainfall in Costa Rica has triggered extensive landsliding.  This video shows a very lucky escape for a motorcyclist:

It is of course only a small landslide, but illustrates nicely the dangers posed by even apparently superficial soil slides.

Ongoing landslides in northern India

Meanwhile northern India and Pakistan have been affected by heavy rainfall that has caused extensive damage (though has received very little coverage). This landslide in Ramban District appears to be causing considerable disruption to the road:

 

 

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8 September 2014

The Sunkoshi landslide dam breach

The Sunkoshi landslide dam breach event

On Saturday night, apparently without warning, the landslide dam on the Sunkoshi River in Nepal abruptly breached, allowing the lake to mostly drain.  This event appears to have occurred without warning, such that one of the Nepal Army excavators was washed away.  The breach event appears to have been natural – a response to heavy rainfall – rather than a result of the attempts by the Nepal Army to widen the channel.  Whilst some damage has been reported downstream, the flood does not appear to have been exceptionally large, so no casualties have been reported. Republica has a very nice set of photographs of the breached lake and dam:

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Whilst Kapil Dhital (@bewitchkapil) tweeted this image of the lake this morning:

Sunkoshi landslide dam breach

Khapil Dhital (@bewitchkapil) via Twitter

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So what caused the breach?  This is the gauging data for the Bharabise station (upstream of the dam) and the Pachuwaghat station (downstream).  Note that the two sets of data use different y-axes. The flood peak generated by the breach event is very clear at Pachuwarghat, although this is not a very high peak.  The Bharabise station probably responded to rainfall – there is a dramatic increase in discharge a few hours before the flood wave reached Pachuwarghat.  Thus, it appears that the breach was initiated by this sudden increase in river flow in response to heavy rainfall:

Sunkoshi landslide dam breach.

This is clearer when the data for the few hours before the breach event are plotted:

Sunkoshi landslide dam breach

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In many ways this is the best possible outcome.  The release of most of the water means that the hazard has in effect been removed, but without causing a huge amount of damage downstream.  Unfortunately the huge amount of resource and effort that has gone into building the two new roads has been wasted.  Once again I would reiterate my opinion that a focus on deepening the channel, rather than widening it and building new roads, would have been a much more effective way to manage this hazard.  That the dam breached in a rainfall-induced event suggests that a targeted effort to deepen the channel could have resolved the crisis much earlier.

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24 August 2014

Sunkoshi landslide in Nepal – still no reduction in the lake level

Sunkoshi landslide – draining the lake

The Nepal Army is continuing in its attempts to drain the Sunkoshi landslide-dammed lake.  Whilst the threat of a breach event has now subsided (though it has not gone completely of course), the major emphasis is on re-establishing the trade link to Tibet.  There can be little doubt that considerable effort has been expended, but the results are shown in these two photographs of the lake, tweeted by Kapil Dhital.  This is the lake on 6th August:

Sunkoshi landslide

Photo by Kapil Dhital via Twitter

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And this is the image he tweeted yesterday – 17 days later:

Sunkoshi landslide

Photo by Kapil Dhital via Twitter

 

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One really does not need to be a trained photographic interpretation expert to see that the lake level has not fallen, despite the best efforts of the Nepal Army.  I have done a quick search on the Republica and other Nepal websites for news stories about the lake level behind the Sunkoshi landslide dam:

On 8th August, Republica reported that “The water level in the Sunkoshi River in Sindhupalchowk that increased last Saturday after a massive landslide blocked the river, has started to increase even after the Nepal Army blasted outlets…The water flow in the river was recorded at 180 cusec on the day of the landslide, but now it has reached 300 cusec, Singh said quoting the army technicians.”

On 9th August: “The inflow of water in the artificial lake was 205 cusec while the outflow was 210 cusec, and the water level has decreased by seven centimeters by Saturday, according to a statement issued by NA´s Directorate of Public Relations. The army plans to release accumulated water in the artificial lake, and resume the obstructed Kodari highway at the earliest, the statement added.”

On 10th August: “The water level in the artificial lake formed after the recent landslide occurred at Jure, Sindhupalchowk blocking the Sunkoshi River has increased.  The Nepal Army (NA) team carried out three blasts targeting the blocked sites today to ease water flow of artificial lake, said Deputy Superintendent of Police Bharat Bahadur Bohora.”

On 11th August: “If we managed to reduce water level by 10 meters, we can bring the submerged road into operation within another three days,” Sitaula [secretary of the Ministry of Physical Infrastructure and Transport] said. “As the dam was filled in 11 hours, we can drain it out by doubling water flow downstream.”

On 13th August: “Nepal Army on Wednesday carried out eight blasts to resume the regular course of the Sunkoshi River that was blocked following a massive landslide at Jure of Ramche VDC-5 in Sindhupalchowk district on August 2…As per the measurement carried out in the afternoon the internal water current in the artificial lake is 255 cubic sec while the external current stands at 397 cubic sec.”

On 17th August: “The water level in artificial lake formed after massive landslide at Jure blocked Sunkoshi River, is gradually decreasing with increase in water outflow from the reservoir after Nepal Army (NA) constructed another channel to drain out dammed water…According to NA Brigadier General Ashwin Kumar Thapa, the water level has decreased by 75 centimeters after excavators were used to increase water outflow. “The water level in the dam is decreasing at the rate of two centimeters per hour,” he said.   He further informed that water inflow in the artificial lake is 180-200 cumec, while outflow of water from the reservoir is 350 cumec “The current water inflow rate is normal rate for Sunkoshi River during Monsoon,” he said.  During three-days of torrential downpour both water inflow and outflow were high with outflow and inflow rate standing at 330 cusec and 530 cusec respectively.”

On 19th August a different message emerges: “Although 900,000 kg/meter water is exerting pressure on the landslide dam [note - this statistic cannot be correct for a lake less than 50 m deep], the huge rock material is strong enough to withstand the pressure, the NA said organizing a press conference at its headquarters in Kathmandu.  “We cannot open large outlets for the pooled water as that may cause more flooding downstream,” Geologist from the Tribuvan University Ranjan Kumar Dahal said. Also, it is very costly to completely remove the landslide debris, he said. He said it might cost Rs 450 million to remove the whole debris, which is almost impossible. The water level above the landslide dam has so far decreased just by a meter. NA also clarified that it can´t carry any strong blast to make the water exit from the dam.”

On 20th August, eKantipur reported that: “The Nepal Army team, entrusted to drain the landslide-dammed lake in the Sunkoshi river, plans to bring down the water level by 15 metres in the next 30 days, said army officials…“In the last few days, we’ve been able to reduce the level of water by a metre,” said Niranjan Kumar Shrestha, assistant spokesperson for the Army.  The Army plans to widen the smaller of the channels currently draining the lake to bring down the water volume.”

On 23rd August the Himalayan Times reported that: “In a bid to ease outflow of water…Nepal Army carried out two controlled blasts on Saturday. NA Directorate of Public Relations said the average inflow in the artificial lake as of this afternoon is 187 cusec whilst the average outflow is 280 cusec”

On 24th August the Himalayan Times reported that: “Issuing a statement on Monday, NA’s Directorate of Public Relations said the Army’s efforts to remove the obstruction…are also ongoing.  According the the statement, while the inflow of water in the river was measured at 193 cusec this afternoon, the outflow was recorded at 303 cusec”

In recent days the media has repeatedly reported that the outflow is greater (often much greater) that the inflow.  If so the water level should be declining quickly, which is clearly not the case.  Thus, the figures must be wrong or misleading, so I am bemused as to why they are repeatedly reported in this way.

The sad reality is that all of the immense effort that has gone into building the two channels has had no impact on the net lake level.  The reasons are probably demonstrated in this image from the Nepal Army:

Sunkoshi landslide

Photo: Department of Public Relations, Nepal Army

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Widening the channel is of course no bad thing, but to achieve a drawdown of the lake level behind the Sunkoshi landslide dam the channel bed needs to be deepened.  The lake level will not change in aggregate without deepening the channel.

Finally, Kapil Dhital tweeted this image of the private road being constructed by local entrepreneurs:

Sunkoshi landslide

Picture from Kapil Dhital via Twitter

 

Issuing a statement on Monday, NA’s Directorate of Public Relations said army’s efforts remove the obstruction created by the landslide on the course of Sunkoshi River in Sindhupalchok has are also ongoing. According to the statement, while the inflow of water in the River was measured at 193 cusec this afternoon, the outflow was recorded 303 cusec. – See more at: http://www.thehimalayantimes.com/fullNews.php?headline=NA+continues+rescue+efforts+in+disaster-hit+areas&NewsID=425198#sthash.2Cp396XN.dpuf
In a bid to ease outflow of water in theSunkoshi River blocked due to August 2 landslide, Nepal Army (NA)carred out two controlled blasts on Saturday.NA Directorate of Public Relations said the average inflow in the artificial lake as of this afternoon is 187 cusec whereas the average outflow is 280 cusec. – See more at: http://www.thehimalayantimes.com/fullNews.php?headline=NA+carries+out+controlled+blasts+to+ease+Sunkoshi+outflow&NewsID=425102#sthash.SS6WWD44.dpuf
In a bid to ease outflow of water in the Sunkoshi River blocked due to August 2 landslide, Nepal Army (NA) carred out two controlled blasts on Saturday.NA Directorate of Public Relations said the average inflow in the artificial lake as of this afternoon is 187 cusec whereas the average outflow is 280 cusec. – See more at: http://www.thehimalayantimes.com/fullNews.php?headline=NA+carries+out+controlled+blasts+to+ease+Sunkoshi+outflow&NewsID=425102#sthash.SS6WWD44.dpuf
In a bid to ease outflow of water in the Sunkoshi River blocked due to August 2 landslide, Nepal Army (NA) carred out two controlled blasts on Saturday.NA Directorate of Public Relations said the average inflow in the artificial lake as of this afternoon is 187 cusec whereas the average outflow is 280 cusec. – See more at: http://www.thehimalayantimes.com/fullNews.php?headline=NA+carries+out+controlled+blasts+to+ease+Sunkoshi+outflow&NewsID=425102#sthash.SS6WWD44.dpuf
In a bid to ease outflow of water in the Sunkoshi River blocked due to August 2 landslide, Nepal Army (NA) carred out two controlled blasts on Saturday.NA Directorate of Public Relations said the average inflow in the artificial lake as of this afternoon is 187 cusec whereas the average outflow is 280 cusec. – See more at: http://www.thehimalayantimes.com/fullNews.php?headline=NA+carries+out+controlled+blasts+to+ease+Sunkoshi+outflow&NewsID=425102#sthash.SS6WWD44.dpuf
In a bid to ease outflow of water in the Sunkoshi River blocked due to August 2 landslide, Nepal Army (NA) carred out two controlled blasts on Saturday.NA Directorate of Public Relations said the average inflow in the artificial lake as of this afternoon is 187 cusec whereas the average outflow is 280 cusec. – See more at: http://www.thehimalayantimes.com/fullNews.php?headline=NA+carries+out+controlled+blasts+to+ease+Sunkoshi+outflow&NewsID=425102#sthash.SS6WWD44.dpuf

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Whilst the frustration that has driven the local people to do this is understandable, the environmental consequences of this road are clear.  And, of course, this road will be very prone to landslides, especially as the lake will have elevated the water level in the slopes.  I would not want to be on this road is heavy rainfall.

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23 August 2014

Dariali Gorge: another very large landslide from the Devdoraki glacier

Dariali Gorge landslide number 2

In May this year a very large landslide occurred at Devdoraki in Georgia, blocking the strategically-important Dariali Gorge.  This transpired to be a large rockslope failure from directly below the glacier, which turned into a high speed, long runout flow.  I was lucky enough to be able to feature some images of the landslide.

On 20th August, another landslide occurred at the same site, once again blocking the Dariali Gorge.  This landslide, which is reported to have originated at the glacier, is reported to have been larger.  The trigger was reportedly heavy rainfall.  The landslide, and the resulting damage, are sufficiently serious to have needed a visit to the site by the President of Georgia.  Two people lost their lives in the landslide, both workers from the nearby HEP project.

There are some images on the internet of the landslide.  The best that I have found are on this Georgian news website.  At times it is not entirely clear what they are showing, but they are interesting nonetheless.  I suspect that these two images show the landslide deposit itself – it appears that the landslide blocked the river, which has then breached the dam to create an outburst flood(?):

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An interesting aspect of this is the landslide deposit marks on the valley walls, which suggest that a very substantial volume of material has been eroded away.  It is not clear to me whether this is from the May or the August landslide events.

This image seems to show downstream damage from the outburst flood:

 

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In many ways this image is the most interesting.  It is possible that it shows the channel through which the landslide travelled to reach the Dariali Valley, although this is speculation at best:

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It would be fascinating to see a set of images of the source and track of this landslide – to have two very mobile, long runout landslides in the same valley in a short period is both unusual and intriguing.  Does anyone know if such a set of images has been posted online?

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21 August 2014

Hiroshima: disastrous landslides with further rainfall warnings in effect

Hiroshima landslides

On Wednesday, a suburb of Hiroshima in Japan was struck by a series of catastrophic rainfall-induced landslides, which resulted from a period of prolonged and exceptionally heavy rainfall.  These landslides are reported to have killed 39 people, with as many as a further 43 people reported to be missing.  Sadly, some of the deaths appear to be rescue staff who were overcome by subsequent slides.

From a technical perspective, the best images I have found of these landslides are on the IBT website, which includes this overview of the site:

Hiroshima

Reuters via IBT

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These landslides appear to be channelised debris/mud flows.  It appears that they have started as small failures along watercourses that have entrained large volumes of material to become highly destructive flows.  It appears that they have mostly consisted of very fine-grained materials, which is consistent with the bedrock geology, which is reportedly weathered granite.

Unfortunately, there is further heavy rainfall forecast for this area, and at the time of writing Robert Speta tweeted the following:

The image shows a line of storms approaching the area:

Hiroshima.

Whilst it seems unlikely that this rain will cause as much damage in Hiroshima itself, landslide and flood warnings are in force across the region and there have been many evacuations.

 

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18 August 2014

Sunkoshi landslide: another update

Sunkoshi landslide

ICIMOD has released a report about the Sunkoshi landslide, which has been reported in The Himalayan Times.  The most interesting aspect may be some statistics on the landslide, which appeared in a tweet by Kanak Mani Dixit, which said:

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These statistics are in line with those generated elsewhere, but are the first to provide a complete set.  The main thrust of the ICIMOD report (which I’ve not seen) seems to be that more investigation of the Sunkoshi landslide itself, and more detailed landslide hazard mapping in general, are required.  It is hard to disagree with these suggestions.

Meanwhile, the Nepal Army continue to try to drain the lake, but the degree to which they are being successful is very unclear.  There is a profound deficit of reliable information about the state of play at the dam site – over the last two weeks there has been a number of reports that the lake level was falling, all of which have proven to be incorrect.  The latest reports, on Sunday, were that:

The water level in artificial lake formed after massive landslide at Jure blocked Sunkoshi River, is gradually decreasing with increase in water outflow from the reservoir after Nepal Army (NA) constructed another channel to drain out dammed water.  Decline in water level could be clearly witnessed on Sunday as clouds separated revealing blue sky after three days of torrential downpour came to an end.

According to NA Brigadier General Ashwin Kumar Thapa, the water level has decreased by 75 centimeters after excavators were used to increase water outflow. “The water level in the dam is decreasing at the rate of two centimeters per hour,” he said.  He further informed that water inflow in the artificial lake is 180-200 cusec, while outflow of water from the reservoir is 350 cusec. “The current water inflow rate is normal rate for Sunkoshi River during Monsoon,” he said.

During three-days of torrential downpour both water inflow and outflow were high with outflow and inflow rate standing at 330 causes and 530 causes respectively.

But what does this mean?  The figures above suggest that during the heavy rainfall the inflow exceeded the outflow, which means that the lake level must have risen.  Then, when the rain stopped the inflow reduced to a level below outflow, so the lake level must have fallen.  This is quite normal dam hydraulics.  A key question is whether the net (i.e. low flow) level of the lake has fallen.  The data being provided are not adequate to judge this. 

The key to reducing the level of the lake has to be to lower the bed of the channel.  Widening the channel, or creating a new one, will make the discharge of storm flow more efficient – i.e. the lake level won’t rise so much in the next heavy rainfall event.  But to meaningfully draw down the lake the channel bed has to be lowered.  Now this is of course risky – in particular if the bed of the stream is being armoured by large boulders, then these have to be blasted.  But, this could be the case that beneath the boulders lie fine-grained deposits that might erode quickly once exposed.  So this sort of operation is very sensitive and challenging, and requires high levels of expertise.  And this is why I still contend that the Nepal Army should be seeking assistance from groups that have managed these problems before, most notably the Chinese.  They might note the speed and efficiency of the operation to drain the valley blocking landslide in Yunnan Province, despite the very challenging access problems.

If the Nepal Army wants to drain the lake then the engineers have to deepen the channel.  The challenge is to do this is a safe way. Why not get assistance from the Chinese team whose raison d’etre is to manage valley blocking landslides?  After all, China wants this important trade link open too.

Finally, an additional dimension is the rapidly escalating pressure to reopen the road to Tibet.  The Nepal Engineers Association is pressing for concerted efforts to drain the lake and construct an alternative road to bypass the Sunkoshi landslide.  In a separate development, a group of local entrepreneurs have started to construct a new alignment with a bulldozer:

sunkoshi landslide.

Whilst I can understand the frustration that is driving this, the track shown above is both environmentally catastrophic and a recipe for further landslides.  It seems unlikely that it is a sustainable solution.

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15 August 2014

Continuing landslide turmoil in Nepal

The Sunkoshi landslide in Nepal – an update

Landslides continue to cause major disruption in Nepal as the summer monsoon intensifies.  At Sunkoshi, the major river-blocking landslide continues to confound the attempts by the army to draw down the lake, despite the presence of heavy machinery and now over 50 controlled blasts by the Nepal Army. Indeed, in the heavy rainfall of the last few days reports suggest that the lake level has risen by 50 cm.

I think that there is little doubt that the Nepal Army has been working very hard on this problem, and deploying resources extensively.  However, the communications side of the work has gone less well, with repeated statements that the lake level is falling and/or that the problem would be solved within a day or two.  This has been proven to be erroneous and overly-optimistic.  Unfortunately, the press have taken such statements at face-value, which in turn has generated a huge backlash when the problem could not be resolved.  eKantipur today has an article entitled “Shame On You!”, which is strongly critical of the government’s efforts in dealing with all aspects of the landslide.  As Nepal moves towards the Desain holiday, which is important for shopping, and imports from the north remain impossible, these pressures are going to rapidly grow.

The bottom line is that there is now a need to both implement a proper communications plan, which should emphasise the need to view this as a long term project (whilst recognising that a rapid breach event can still occur), and to call for expert assistance, in particular from China, where there is considerable expertise in managing these issues.  Based on experience elsewhere I  suspect that there will be a need to either block the existing channel to blast the base (not an option during the monsoon, and probably not in the dry season either because the dam has so little freeboard across the entire width) or to build a new channel from the foot of the dam upwards.  This is a major project that will take some time, assuming that the dam does not breach first.  As usual the lack of information about the structure of the dam is a major issue, meaning that its behaviour is unpredictable.

Heavy rainfall across Nepal and N. India causes high levels of loss

Meanwhile, very heavy monsoon rainfall across Nepal and northern India over the last few days has generated high levels of losses from landslides and floods.  For example, Republica is reporting 53 people killed and 75 missing in Nepal, although this figure may change considerably as news filters through.  Chisapani in West Nepal reportedly received 545 mm of precipitation in 24 hours.  At least 23 people have been killed in northern India too.  TRMM highlights the areas likely to have been affected by the landslides, which extends along much of the Himalayan Arc:

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12 August 2014

The Eaglepointe Landslide in Salt Lake City, Utah

The Eaglepointe landslide

One of the many landslide events in the last few days was a slide in the Eaglepointe subdivision in Salt Lake City in Utah.  The development of this landslide was brilliantly caught on a time-lapse video by KUTV reported Holly Menino and 2News photographer Mike Stephen:

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Jeff Moore of the University of Utah has very helpfully put together the following incredibly useful briefing on the Eaglepointe landslide:

  • On Tuesday morning Aug 5, around 6 am, a large landslide underwent rapid and sustained failure, displacing some tens of meters over a period of minutes.
  • One house was destroyed and three others imminently threatened.  A nearby gas pipeline was undamaged.
  • Movement had initiated at least four months prior back in April (our wet season), by some accounts back in fall 2013.
  • In the week before the slide, large tension cracks had been growing at the crest of the slope, and the toe area was bulging creating some distress to adjacent properties.
  • The developer hired geotechnical consultants to install inclinometers at the crest, and homeowners were diligently observant of the slope.
  • Residents had received a letter indicating that there was a slide and to be prepared, but most seem to have already known due to the obvious signs of ground distress.
  • During the morning of the failure, rolling boulders from the toe woke one of the 12 residents in the destroyed home, who then woke the rest of his extended family and everyone evacuated from the house before it collapsed.
  • Movement later slowed but the scarp and slide mass threaten more homes.
  • A heavy monsoon rain storm the previous evening is the ascribed trigger of ultimate movement, although slow displacement had been ongoing for months.
  • My preliminary volume estimate of the slide is ~300,000 m3, based on the aerial extent and an assumed average depth of 10 m.
  • The slide mass consists of sands and gravels of the Lake Bonneville highstand, overlain atop Tertiary volcanic tuff – the latter is a notorious material for landslides in the northern Utah, the so-called Norwood Tuff.  It weathers to swelling, water-sensitive clays. The condition or depth of the sliding surface is however, not known at this time.
  • Another slide just 1 km away in similar stratigraphy (named Springhill) destroyed several homes over an extended period in 1998 and during later wet years.  Yet another slide in the same geology is progressively destroying several residential lots in nearby City Creek.
  • The development was a gravel quarry until the late 1990′s, and the area that slid was the highwall or maximum extent of quarrying.  It had been graded at 2:1 (~25 degrees).  The houses threatened were built in the mid-2000′s.  New development is currently underway at the crest of the slope that failed, including new roads and several new homes.
  • Geotech reports used by the developer and city to permit the previous and new construction deemed the slope globally stable.  These can be downloaded and freely reviewed here: http://nslcity.org/index.aspx?NID=331
  • Some smaller sluffs and slides had been observed in previous years especially around the base of the slope where small cut-backs had been made.
  • Location: https://www.google.com/maps/@40.8274081,-111.9022917,295m/data=!3m1!1e3 – to the north of the slope you can see the covered tennis courts and home immediately west that sustained the most damage, as well as some clearing for development at the crest of the slope (south).

Standard.net has a great gallery of images of the landslide.  This image from that set shows the state of the eaglepointe landslide site now:

Eaglepointe

http://www.standard.net/Local/2014/08/06/North-Salt-Lake-residents-blame-city-for-landslide.html

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Given the history of the site I think that it is unlikely that the Eaglepointe landslide can be considered to be a natural event.  However, it is not clear to me who, if anyone, might be to blame.

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