First, it is clear that this was not an engineered failure – in other words, it was not planned.\u00a0 There was some discussion on Twitter and in the comments that this was the failure of a fuse plug – i.e. a designed failure point that would release water to prevent overtopping<\/a>.\u00a0 I can find no evidence that Edenville Dam<\/a> had a fuse plug, and I do not think that a fuse plug failure would behave in the way shown in the video.<\/p>\n Planet Labs<\/a> have a wonderful high resolution image of the aftermath of the failure; I wpould be surprised if a fuse plug is intended to leave this type of catastrophic breach:-<\/p>\n Planet Labs image<\/a> of the aftermath of the Edenville dam breach. Image copyright of Planet Labs<\/a>, used with permission.<\/p><\/div>\n .<\/p>\n The style of failure<\/a> implies that the dam had become saturated in this area.\u00a0 A key question is going to be why this happened.\u00a0 One suggestion is that the water level exceeded the impermeable barrier, allowing water to flow into the structure. An alternative is that the dam was suffering from seepage prior to the floods.\u00a0 The Google Earth imagery is interesting – this image is from 2018:-<\/p>\n Google Earth image of the site of the Edenville dam breach.<\/p><\/div>\n .<\/p>\n Is there an indication here that there was deformation in the dam? Or that works had been undertaken?\u00a0 I’m not sure.\u00a0 It will be interesting to see both the monitoring records for the dam and the maintenance that had been undertaken, as well as the design cross-sections.<\/p>\n The mechanism of failure is undoubtedly a rotational slip<\/a>.\u00a0 It is possible that this started as a smaller failure at the crest of the dam, which then drove a larger failure in the main face.\u00a0 However, I favour the interpretation that high pore water pressures, and a loss of unsaturated conditions, through the dam volume drove the failure.\u00a0 There are some indications in the video that high pore water conditions were present in the lower part of the structure.<\/p>\n Readers have rightly pointed out that earthfill embankment dams<\/a> are not unusual and, when well designed and maintained, they are not unsafe.\u00a0 This dam was completed in 1924.\u00a0 However, these structures do require maintenance – would you expect a train built in 1924 to still work without extensive restoration – and they were designed for a time when rainfall levels were different.\u00a0 Climate change – global heating – is driving increases in rainfall intensities and durations, meaning that the Probable Maximum Flood is increasing in very many places.<\/p>\n I always get howls of protest when I say that climate change is important, but it is the case. These structures, worldwide, are going to need a substantial upgrade to cope with that increase in rainfall, and that’s going to be very expensive.\u00a0 In the interim we will see more failures of this type.<\/p>\n There is also some interesting analysis of the performance of the dam prior to failure online, using INSAR data<\/a>.\u00a0 It is astonishing that such an interpretation can be generated so quickly.\u00a0 At present I find it hard to interpret this data though – the results seem to indicate deformation across much of the structure, and the section that failed seems to show uplift not, as I would expect, subsidence.\u00a0 This needs further work, but INSAR remains an exceptionally exciting<\/a> area of work for these types of investigations, and for pre-failure monitoring.<\/p>\n The failure of the dam is a catastrophe for people living in this area.\u00a0 Planet Labs have an online gallery of high resolution images of the impacts<\/a>.\u00a0 The Planet Labs<\/a> image below shows some of the downstream flooding for example:<\/p>\n Planet Labs image<\/a> of the aftermath of the Edenville dam breach. Image copyright of Planet Labs<\/a>, used with permission.<\/p><\/div>\n .<\/p>\n But we must not forget that the effects lie upstream as well.\u00a0 There are numerous houses located around the lakes whose value will have been based upon the proximity to the water.\u00a0 The failure of the dam will have a profound impact, and of course the ecology of the lakes will also have been destroyed.<\/p>\n .<\/p>\n The past 24 hours have been my most successful day in the 12 years of this blog, with almost 50,000 individual visits.\u00a0 Thank you.<\/p>\n .<\/p>\n In Teignmouth in Devon in SW England there is controversy over plans by Network Rail<\/a> to change the alignment of Isambard Kingdom-Brunel\u2019s wonderful Great Western Railway to protect it against landslides.\u00a0 The article claims that the cost of these works is \u00a3500 million.<\/p>\n .<\/p>\n![\"Edenville](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/05\/20_05-Edenville-8-scaled.jpg\")
![\"Edenville](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/05\/20_05-Edenville-7-scaled.jpg\")
![\"Edenville](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2020\/05\/20_05-Edenville-9-scaled.jpg\")
On reflection 1: my most successful blog day<\/h4>\n
On reflection 2: Controversy over the protection of the Great Western Railway in Devon from landslides<\/h4>\n
Reference<\/h4>\n