The project is running late and over budget.\u00a0 In 2006 the estimated cost of the project was $554 million<\/a>. By July 2015 this had reached $1.74 billion.\u00a0 The project was meant to be completed in November 2016, but in April 2017 this had slipped to December 2022, a delay of over six years.\u00a0\u00a0 BBS reported in February 2019<\/a> that the completion date had slipped to 2024; I assume that the budget has escalated as a result.<\/p>\n The primary cause of this delay is a landslide. In July 2013 the east-facing bank of the project site failed and displaced by more than 5 metres.\u00a0 This landslide has required extensive mitigation.\u00a0 However, the project suffered another major, and on this occasion fatal, landslide January 2019<\/a>.<\/p>\n Google Earth imagery shows the extensive works underway to mitigate the east-facing slope, allowing the abutment of the dam to be completed.\u00a0 The Google Earth image below shows the site in 2017.\u00a0 I have placed the marker at what appears to be the crown of a slope failure, although Dini et al.<\/em> (2020<\/a>) suggest that it extends further up the slope:-<\/p>\n The site of the landslide at the Punatsangchhu I dam, via Google Earth.\u00a0 The image provides the coordinates of the site.<\/p><\/div>\n .<\/p>\n The paper by Dini et al.<\/em> (2020<\/a>) uses InSAR to monitor the movement of the east-facing slope at the Punatsangchhu I dam site.\u00a0 One of the great things about InSAR is that it allows us to go back in time to look at movements that occurred 15 or more years ago.\u00a0 Their findings make uncomfortable reading. First, the slope was displacing in 2007, even though construction started in 2009.\u00a0 In other words, the dam appears to be located by a large, ancient creeping landslide.\u00a0 Second, portions of the slope have continued to move throughout the construction period, and indeed the area of active displacements continued to expand right through to 2018, the end of the study period. The paper notes that<\/a>:<\/p>\n Stabilisation measures currently only focus on a small portion of the slope, however, the unstable area is larger than previously evaluated.\u00a0<\/em><\/p>\n And third, that the site is probably a large, ancient landslide.\u00a0 Dini et al.<\/em> (2020<\/a>) have found evidence of movement over an area of 8 km2<\/sup>.\u00a0 They include this Google Earth image of the site:-<\/p>\n The site of the landslide at the Punatsangchhu I dam, via Google Earth. Image from Dini et al. (2020)., who state that the “hatched area represents damaged rock (diagonal) and undisturbed residual soil (vertical)”. The rectangle highlights the area of the 2013 failure.<\/p><\/div>\n .<\/p>\n The InSAR data in Dini et al.<\/em> (2020<\/a>) shows different areas of movement across this large slope, covering about 60% of the total area.\u00a0 The authors include that this might be a deep seated gravitational displacement.<\/p>\n This tale is a classic illustration of the importance of site investigation and of understanding the behaviour of the landscape in these high mountain areas.\u00a0 Loyal readers will know that I have highlighted previously that many large hydroelectric schemes in high mountain areas are not managing slopes sufficiently<\/a>, with tragic and expensive consequences.\u00a0 The Google Earth image below shows the upper portion of the large rock slope. The morphology here, of a steep upper section and then a more planar mid-slope, would always make me deeply suspicious about the presence of an ancient landslide, and indeed when I worked in the Himalayas back in the early 2000s that is how we mapped such sites:-<\/p>\n <\/p>\n The upper portions of the site of the landslide at the Punatsangchhu I dam, via Google Earth.<\/p><\/div>\n .<\/p>\n so, I’m deeply intrigued as to whether this large slope was identified as being problematic before the project started.<\/p>\n .<\/p>\n The debate about the role of landslides, versus tectonic deformation, in the initiation of the 2018 Sulawesi tsunami rumbles on.\u00a0 A new paper concludes that landslides probably did play a role<\/a>.<\/p>\n .<\/p>\n In Sudbury, Canada a man was rescued after spending more than 12 hours trapped in a landslide<\/a>.\u00a0 He has a broken arm.<\/p>\n .<\/p>\n![\"Punatsangchhu](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/05\/20_05-Bhutan-1.jpg\")
![\"Punatsangchhu](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/05\/20_05-Bhutan-2.jpg\")
![\"Punatsangchhu](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/05\/20_05-Bhutan-3-scaled.jpg\")
On reflection 1: landslides at the 2018 tsunami in Sulawesi<\/h4>\n
On reflection 2: A lucky escape<\/h4>\n
Reference<\/h4>\n