{"id":151276,"date":"2024-10-10T13:17:41","date_gmt":"2024-10-10T13:17:41","guid":{"rendered":"https:\/\/news.talkwithrattan.com\/index.php\/2024\/10\/10\/what-leads-rivers-to-suddenly-change-course\/"},"modified":"2024-10-10T13:17:41","modified_gmt":"2024-10-10T13:17:41","slug":"what-leads-rivers-to-suddenly-change-course","status":"publish","type":"post","link":"https:\/\/news.talkwithrattan.com\/index.php\/2024\/10\/10\/what-leads-rivers-to-suddenly-change-course\/","title":{"rendered":"What leads rivers to suddenly change course?"},"content":{"rendered":"<div style=\"text-align:center\"><\/div> \r\n<br><div data-component=\"video-embed\">\n\t\t\t\t\n\n\n\n\n<p>Shifting is in a river\u2019s nature. But when a river breaks free of its channel and carves a new path across the landscape, devastating floods may descend upon communities with little to no warning.<\/p>\n\n\n\n<p>For decades, researchers have struggled to explain exactly how river channels become primed for such sudden diversions, or avulsions. A study published September 18 in <em>Nature<\/em> may have finally quelled the debate, showing how <a href=\"https:\/\/www.nature.com\/articles\/s41586-024-07964-2\" target=\"_blank\" rel=\"noopener\">two factors work together to stage the rerouting of a river<\/a>. Building on their findings, the researchers also developed a promising algorithm that can predict the new path of a river that has avulsed.<\/p>\n\n\n<aside class=\"sn-conversion rich-text rich-text--with-sidebar\">\n<style><![CDATA[\n.email-conversion {\n  border: 1px solid #ffcccb;\n  color: white;\n  margin-top: 50px;\n  background-image: url(\"\/wp-content\/themes\/sciencenews\/client\/src\/images\/cta-module@2x.jpg\");\n  padding: 20px;\n  clear: both;\n}\n\n]]><\/style>\n\n\n\n<div class=\"rich-text embedded-conversion-content is-layout-flow wp-block-group-is-layout-flow\"><div class=\"wp-block-group__inner-container\">\n<style><![CDATA[\n#dynamic-wrapper {\n  border: 1px solid #ffcccb;\n  background-image: url(\"https:\/\/i0.wp.com\/www.sciencenews.org\/wp-content\/uploads\/2024\/03\/032624_sb_space-sugar_feat.jpg?w&#61;800&amp;ssl&#61;1\");\n  background-size: cover;\n  background-position: center center;\n  padding: 20px;\n  clear: both;\n}\n\n#dynamic-conversion {\n  padding: 20px;\n  background:rgba(0,0,0, 0.5);\n  color: white;\n}\n\n#dynamic-conversion h2 {\n  color: white;\n}\n\np.has-text-align-center a {\n  color: white !important;\n  text-decoration: none;\n  font-weight: bold;\n}\n\n]]><\/style>\n\n\n\n<div id=\"dynamic-wrapper\" class=\"wp-block-group\"><div class=\"wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained\">\n<div id=\"dynamic-conversion\" class=\"wp-block-group\"><div class=\"wp-block-group__inner-container is-layout-flow wp-block-group-is-layout-flow\">\n\n\n\n\n<h2 class=\"wp-block-heading has-text-align-center\"><strong>Tell us about your Science News experience<\/strong><\/h2>\n\n\n\n\n\n\n\n<p class=\"has-text-align-center\">Help us improve by taking our 15-question reader survey.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n<\/div><\/div>\n\n\n\n\n<\/div><\/div>\n<\/div><\/div>\n\n\n\n<\/aside>\n\n\n<p>\u201cThese are monumental floods, civilization-changing floods in some cases,\u201d says sedimentologist Douglas Edmonds of Indiana University in Bloomington. In 2010, avulsions on the Indus River in Pakistan contributed to <a href=\"https:\/\/rock.geosociety.org\/gsatoday\/archive\/23\/1\/article\/i1052-5173-23-1-4.htm\" target=\"_blank\" rel=\"noopener\">flooding that forced roughly 20 million people from their homes<\/a>. Nonetheless, flood hazard models remain unable to predict where rivers will reroute, Edmonds say. \u201cIt\u2019s really an invisible flood hazard.\u201d<\/p>\n\n\n\n<p>Avulsions require a setup and <a href=\"https:\/\/www.sciencenews.org\/article\/ancient-earthquake-changed-ganges-river\">a trigger<\/a> \u2014 an overburdened camel\u2019s back and a final straw (<em>SN: 6\/28\/24<\/em>). \u201cThe trigger could be a flood, an earthquake, it could be a logjam in a river,\u201d Edmonds says. The setup refers to how the deposition of sediment has primed a river for diverting \u2014 and it\u2019s the fundamental cause of avulsion, Edmonds says. \u201cRivers experience floods all the time, but they don\u2019t avulse all the time.\u201d<\/p>\n\n\n<div class=\"wp-block-image  has-aligncenter\">\n<figure class=\"aligncenter size-large\"><figcaption class=\"wp-element-caption\"><span class=\"caption wp-caption-3144465\">The 2004 avulsion of the Manambolo River in western Madagascar is shown in this animation created from false color satellite images. Upstream of the avulsion site, the river is about 1 kilometer wide. Vegetation is highlighted in bright green.<\/span><span class=\"credit wp-credit-3144465\">Landsat Program<\/span><\/figcaption><\/figure><\/div>\n\n\n<p>The new study focused on defining the setup, for which there had been two competing hypotheses. One held that avulsions happen when a river becomes superelevated, or the deposition of sediment raises a river\u2019s water level above the surrounding land. The other contended that avulsions occur when there is a slope advantage, or once the slope of a new, potential path becomes steeper than that of the river\u2019s current path.<\/p>\n\n\n\n<p>Edmonds and his colleagues began by using satellite data to investigate roughly 170 avulsions, noting how far downstream rivers tended to divert. Avulsions were roughly three times as common near river mouths and mountain fronts than in between, they found.<\/p>\n\n\n\n<p>Focusing on 58 river channels for which high-resolution topographical data were available, the researchers measured the superelevation and slope advantage prior to avulsions. They found that superelevation best explained avulsions near the mountains, while slope advantage best explained those near river mouths and deltas.<\/p>\n\n\n\n<p>There\u2019s so much sediment flowing out of the mountains that the rivers just pile it up until they\u2019re superelevated and spill over, Edmonds says. Meanwhile in deltas, there\u2019s a lot of cohesive mud that forms very steep natural leaves around deep channels, and avulsions need a steep slope advantage to start cutting through the levee, he adds.<\/p>\n\n\n\n<div class=\"wp-block-group\"><div class=\"wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained\">\n<figure class=\"wp-block-jetpack-image-compare\"><div class=\"juxtapose\" data-mode=\"horizontal\"><img loading=\"lazy\" decoding=\"async\" id=\"3144471\" src=\"https:\/\/i1.wp.com\/www.sciencenews.org\/wp-content\/uploads\/2024\/10\/093024_no_river-avulsion_inline2a_mobile-1.png?ssl=1\" alt=\"\" width=\"680\" height=\"480\" class=\"image-compare__image-before\"\/><img loading=\"lazy\" decoding=\"async\" id=\"3144478\" src=\"https:\/\/i0.wp.com\/www.sciencenews.org\/wp-content\/uploads\/2024\/10\/093024_no_river-avulsion_inline2b_mobile-2.png?ssl=1\" alt=\"\" width=\"680\" height=\"480\" class=\"image-compare__image-after\"\/><\/div><figcaption>In 2019 the Turkwel River in Kenya avulsed, shifting its mouth on Lake Turkana a couple of kilometers north.<span class=\"credit\">Left: Planet Labs PBC<\/span><span class=\"credit\">Right: Planet Labs PBC<\/span><\/figcaption><\/figure>\n<\/div><\/div>\n\n\n\n<p>These two factors \u2014 slope advantage and superelevation \u2014 work together in an inverse fashion, the researchers found. The more superelevated a river becomes, the less of a slope advantage it needs to avulse, and vice versa. \u201cIt is the first time that anyone\u2019s been able to show that with data,\u201d says Penn State geologist Elizabeth Hajek, who was not involved in the study.<\/p>\n\n\n\n<p>Avulsions occurred when the mathematical product of the two factors surpassed a threshold value, the researchers found. So long as precise topographical measurements of a river\u2019s channel are available, which is more likely for larger rivers and in places with clear skies, you could probably use that threshold metric to identify where avulsions are likely to occur, says geomorphologist Vamsi Ganti of the University of California, Santa Barbara, who was also not involved in the study.<\/p>\n\n\n<aside class=\"sn-conversion rich-text rich-text--with-sidebar\">\n<p class=\"has-text-align-center wp-elements-27c40654034fbeecef6418d6adfe0794\" style=\"color:gray; margin-bottom:0px; font-size:.9rem;\">Sponsor Message<\/p>\n<!-- Tag ID: sciencenews-org_leaderboard_incontent -->\n\n<\/aside>\n\n\n<p>The researchers developed a computer algorithm that highlighted where on a map an avulsed river might go, factoring in the steepness of the terrain and momentum of the river. When tasked with predicting the pathways of 10 past avulsions, the algorithm correctly captured the path of each one. \u201cIt\u2019s a really nice tool,\u201d Hajek says. \u201cIt could be really, really helpful for identifying areas of concern.\u201d<\/p>\n\n\n\n<p>The plan is to develop avulsion hazard maps for the globe or vulnerable regions, Edmonds says. \u201cNow that we have this metric, we can go measure it on rivers all over all over the world.\u201d<\/p>\n\n\n\n\t\t\t<\/div>\r\n<br>\r\n<br><a href=\"https:\/\/www.sciencenews.org\/article\/why-rivers-suddenly-change-course\">Source link <\/a>","protected":false},"excerpt":{"rendered":"<p>Shifting is in a river\u2019s nature. But when a river breaks free of its channel and carves a new path across the landscape, devastating floods may descend upon communities with little to no warning. For decades, researchers have struggled to explain exactly how river channels become primed for such sudden diversions, or avulsions. A study [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":151277,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"tdm_status":"","tdm_grid_status":"","fifu_image_url":"https:\/\/i0.wp.com\/www.sciencenews.org\/wp-content\/uploads\/2024\/10\/093024_no_river-avulsion_inline1.gif?resize=475%2C450&ssl=1","fifu_image_alt":"","footnotes":""},"categories":[606],"tags":[487,648,2201,39544],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/posts\/151276"}],"collection":[{"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/comments?post=151276"}],"version-history":[{"count":1,"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/posts\/151276\/revisions"}],"predecessor-version":[{"id":151278,"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/posts\/151276\/revisions\/151278"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/media\/151277"}],"wp:attachment":[{"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/media?parent=151276"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/categories?post=151276"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/news.talkwithrattan.com\/index.php\/wp-json\/wp\/v2\/tags?post=151276"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}