This type of soil failure now known as a \u2018retrogressive breach failure\u2019 is not uncommon in coastal, river and lake settings, worldwide. Notable locations are the lower Mississippi, Inskip and Amity Points in Eastern Australia and in the sandy estuaries of the Netherlands.<\/em><\/p>\n A small triggering event in submerged (saturated) sand starts the process of \u2018breaching\u2019, well known to operators in the dredging industry. A near vertical wall of sand (the breach) migrates upslope. This wall is temporally stabilised by dilation of the sand skeleton immediately behind the breach causing suction (strain hardening). Granular material (such as sand) is shed from the breach as it migrates upslope and this generates a density current which transports grains offshore before they loose momentum and settle to the bottom.<\/em><\/p>\n As the breach arrives at the shore and migrates further inland, it undermines material above the water table, which topples in and adds further to the density (turbidity) current.<\/em><\/p>\n Konrad points us to a paper (Mastbergen et al.<\/em> 2019<\/a>), which is open access, which describes this failure mechanism in more detail.\u00a0 It includes this explanatory diagram:<\/p>\n A schematic diagram of the retogressive breach failure concept. From Mastbergen et al.<\/em> (2019)<\/a>.<\/p><\/div>\n .<\/p>\n The paper includes a number of other examples of these types of failure.\u00a0 It includes the Inskip landslide in Australia, which I also featured on this blog<\/a>.<\/p>\n .<\/p>\n![\"A](\"https:\/\/blogs.agu.org\/landslideblog\/files\/2021\/03\/21_03-RBF-1.png\")
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