{"id":18867,"date":"2016-06-09T06:59:43","date_gmt":"2016-06-09T06:59:43","guid":{"rendered":"http:\/\/blogs.agu.org\/landslideblog\/?p=18867"},"modified":"2016-06-09T06:59:43","modified_gmt":"2016-06-09T06:59:43","slug":"californian-earthflows-1","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2016\/06\/09\/californian-earthflows-1\/","title":{"rendered":"The response of Californian earthflows to drought"},"content":{"rendered":"
The response of Californian earthflows to drought<\/h5>\n

A really interesting paper has just been published in Geophysical Research Letters examining the response of Californian earthflows to the ongoing, epic drought.\u00a0 This paper was led by Georgie Bennett<\/a>, currently at the US Forest Service and Colorado State University, but who will be joining us here at the University of East Anglia <\/a>in January 2017 as a full faculty member. California has been suffering a serious drought for many years now.\u00a0 In the paper, Bennett et al<\/em> (2016)<\/a> mapped 98 active earthflows in a 140 square kilometre area of the Eel River catchment in California.\u00a0 This is an area with multiple large, often deep earthflows that are an important part of the geomorphic system.\u00a0 I have taken one of the larger earthflows from Google Earth below:<\/p>\n

\"Californian

One of the Californian earthflows mapped by Bennett et al.<\/em> (2016), via Google Earth<\/p><\/div>\n

 <\/p>\n

The mapping was very detailed, undertaken using aerial photographs.\u00a0 The mapping focused not just on the boundaries of the landslides, but also on the displacement of trees located on the landslides, which allowed a calculation of the velocity of the landslides with time.\u00a0 This data was then compared with an index of drought, the commonly-used and widely accepted Palmer Drought Severity Index (PDSI), which has been used previously to show that the 2012-2015 drought in California is unprecedented.<\/p>\n

The results are fascinating – I highlight here two key aspects.\u00a0 First, over the last 70 years or so the velocity of the earthflows has markedly decreased.\u00a0 This image shows the mean velocity, with error bars and the PDSI.\u00a0 It is notable that in recent years the PDSI has become exceptionally low, and\u00a0 the earthflows have responded by slowing down:<\/p>\n

\"Californian

The response of Californian earthflows to drought, from Bennett et al<\/em> (2016)<\/a><\/p><\/div>\n

.<\/p>\n

Bennett et al.<\/em> (2016)<\/a> also looked at the differential response of the Californian earthflows of different depths to the drought conditions.\u00a0 They found that the shallower (typically 5 – 15 m thick) landslides showed quite variable response to the drought conditions, with the majority slowing down but a few actually accelerating.\u00a0 However, all of those deeper than 15 metres decelerated.\u00a0 In some ways I find this a quite surprising result – I would have expected that the deep landslides would have been less susceptible to the climate than the shallow ones.\u00a0 The result is robust, but the cause is not clear and is intriguing.\u00a0 Bennett et al<\/em> (2016)<\/a> suggest that it could be that the shallow landslides respond to short term and local effects (vegetation change, a large storm) that might occur within a drought, whilst the deeper Californian earthflows are just responding to the climate forcing.<\/p>\n

This is a really interesting study, showing very elegantly the ways in which the landslide system is responding to climate change.\u00a0 With greater changes to come in the years ahead as the global climate warms further, we will see many more responses of this type.<\/p>\n

Reference<\/h5>\n

Bennett, G. L., Roering, J. J., Mackey, B. H., Handwerger, A. L., Schmidt, D. A. and Guillod, B. P. 2016.\u00a0 Historic drought puts the brakes on earthflows in Northern California. Geophysical Research Letters<\/em>.\u00a0 Doi: http:\/\/dx.doi.org\/10.1002\/2016GL068378<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

In a paper in Geophysical Research Letters, Georgie Bennett and colleagues have examined the response of Californian earthflows to the ongoing drought. They have found that the landslide have slowed markedly as conditions have become drier.<\/p>\n","protected":false},"author":22,"featured_media":18875,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[544],"tags":[137,196,178,534,469,48],"class_list":["post-18867","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-review-of-a-paper","tag-california","tag-climate-change","tag-drought","tag-earthflow","tag-featured","tag-usa"],"_links":{"self":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/18867","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=18867"}],"version-history":[{"count":0,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/posts\/18867\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media\/18875"}],"wp:attachment":[{"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/media?parent=18867"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/categories?post=18867"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.agu.org\/landslideblog\/wp-json\/wp\/v2\/tags?post=18867"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}