{"id":25792,"date":"2017-09-27T07:17:02","date_gmt":"2017-09-27T07:17:02","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=25792"},"modified":"2017-09-27T07:17:02","modified_gmt":"2017-09-27T07:17:02","slug":"heifangtai-terrace-1","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2017\/09\/27\/heifangtai-terrace-1\/","title":{"rendered":"Heifangtai terrace: spectacular loess flowslides in Gansu Province, China"},"content":{"rendered":"

Heifangtai terrace: a location of spectacular loess flowslides<\/h4>\n

Loess, a windblown silt deposit, mantles about 6% of the land area of China.\u00a0 As I have noted previously<\/a>, these thick loess deposits generate some of the most spectacular landslides on earth<\/a> because of their potential to undergo fluidisation<\/a>, allowing landslides to transition into highly destructive, long runout flowslides.\u00a0 In a recent paper published in the journal Engineering Geology<\/em>, Qi et al<\/em>. (2017)<\/a> describe loess landslides on the Heifangtai terrace, which is located at the confluence of the Yellow River and the Huangshi River in Gansu Province, northwestern China.\u00a0 This terrace, which is located at 36.0916, 103.3089 if you want to take a look, has a cap of about 26-48 metres of loess.\u00a0 It is both populated (primarily by people relocated from the site of a hydroelectric plant) and irrigated.\u00a0 Qi et al<\/em>. (2017)<\/a> describe 17 loess landslides on the margins of the terrace – you can see many of these in the Google Earth image below:-<\/p>\n

\"Heifangtai

Google Earth image of the Heifangtai Terrace in Gansu, China<\/p><\/div>\n

.<\/p>\n

Qi et al<\/em>. (2017)<\/a> highlight in particular a pair of landslides that have developed in the Moshi Gully on the flanks of the terrace between 2004 and 2013.\u00a0 This image shows the site of these two landslides, on the southern edge of the terrace, in December 2004:-<\/p>\n

\"Heifangtai

Google Earth image of the site of the landslides on the edge of the Heifangtai Terrace in 2004<\/p><\/div>\n

.<\/p>\n

By November 2012 notable instability had started to develop at two sites on the terrace edge.\u00a0 I have marked the headscarps of the two landslides.\u00a0 At this stage the landslides appear to have low levels of mobility:-<\/p>\n

\"Heifangtai

Google Earth image from November 2012 showing the two landslides on the Heifangtai Terrace.<\/p><\/div>\n

.<\/p>\n

By February 2015 one of the two landslides, the one further from the camera, had developed significantly.\u00a0 As Qi et al<\/em>. (2017)<\/a> note, this slide had shows retrogression of the headscarp and had started to develop a clear flow-type structure.\u00a0 Note though that the mobility is still low:-<\/p>\n

\"\"

Google Earth image from February 2015 showing the two landslides on the Heifangtai Terrace.<\/p><\/div>\n

.<\/p>\n

But by September 2015 the landslides have changed dramatically:-<\/p>\n

\"Heifangtai

Google Earth image from September 2015 showing the landslides on the Heifangtai Terrace.<\/p><\/div>\n

.<\/p>\n

Both slides have failed spectacularly, with the one in the foreground in particular showing very high mobility and extreme retrogression.\u00a0 Qi et al<\/em>. (2017)<\/a>\u00a0 report that this landslide occurred in a two stage process in April 2015.\u00a0 The first failure, involving 80,000 m3, occurred on 29th April 2015 at 7:50 am.\u00a0 The second happened about three hours later in three distinct phases.\u00a0 The landslide travelled almost 800 metres.<\/p>\n

The most recent image, from May 2017, shows that this landslide has undergone little change, but the other has suffered a further failure event:-<\/p>\n

\"Heifangtei

Google Earth image from May 2017 showing further landslide activity on the Heifangtei Terrace<\/p><\/div>\n

.<\/p>\n

Worryingly, landslide activity is clearly developing on other sections of the terrace edge.<\/p>\n

Reference<\/h4>\n

Xing Qi, Qiang Xu and Fangzhou Liu 2017 Analysis of retrogressive loess flowslides in Heifangtai, China<\/a>.\u00a0 Engineering Geology<\/em>.<\/p>\n","protected":false},"excerpt":{"rendered":"

In a new paper in the journal Engineering Geology, Qi et al. (2017) describe spectacular loess landslides from the Heifangtai terrace in China<\/p>\n","protected":false},"author":22,"featured_media":25803,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_members_access_role":[],"_members_access_error":""},"categories":[544],"tags":[16,881,469,14,232,17,184],"class_list":["post-25792","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-review-of-a-paper","tag-china","tag-east-asia","tag-featured","tag-flowslide","tag-loess","tag-research","tag-review"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/25792","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/users\/22"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/comments?post=25792"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/25792\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/25803"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=25792"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=25792"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=25792"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}