{"id":17133,"date":"2016-06-08T00:11:00","date_gmt":"2016-06-08T07:11:00","guid":{"rendered":"http:\/\/live-hakamagwp.pantheonsite.io\/news\/suddenly-river-runs-through-it"},"modified":"2019-03-20T13:02:45","modified_gmt":"2019-03-20T20:02:45","slug":"suddenly-river-runs-through-it","status":"publish","type":"custom_news","link":"https:\/\/hakaimagazine.com\/news\/suddenly-river-runs-through-it\/","title":{"rendered":"Suddenly, a River Runs Through It"},"content":{"rendered":"

On June 19, 1855, the Yellow River broke through its levees and sent nearly its full flood discharge\u2014more than 2,500 cubic meters of water per second\u2014cascading into low-lying farmland in China\u2019s Shandong province. Though the people living alongside this temperamental waterway were accustomed to frequent flooding, this time was different. This time, the river wasn\u2019t flooding; it was moving. Over years of continuous flooding, the river abandoned its outlet into the Yellow Sea and swept across hundreds of kilometers of land to flow north into the Bohai Sea<\/a>. The river\u2019s sudden redirection triggered civil unrest<\/a>, displaced millions of people, and drowned farms and villages across northeastern China.<\/p>\n

To geologists, this sudden shift in a river\u2019s course is known as an avulsion<\/a>, a hazard that, to this day, strains the fraught relationship between rivers and the communities that rely on them.<\/p>\n

An avulsion is a natural process that can happen without warning. \u201cEach river delta that avulses has its own internal clock,\u201d says Vamsi Ganti<\/a>, a civil engineer at Imperial College London. But based on new research<\/a>, Ganti and his colleagues think they\u2019ve found a way to read this clock\u2014to predict when and where a river may shift course. In the lab, the researchers built a two-meter scale model of a river delta, and used it to identify the mechanisms that determine avulsion onset.<\/p>\n

River deltas naturally evolve over thousands of years as sediment deposits to form large leaf-shaped landforms called\u00a0lobes<\/a>.\u00a0Recent studies<\/a>\u00a0have shown that these lobes will grow to a specific length depending on the depth and gradient of the river that is building them. Once this length is reached, it triggers an avulsion.<\/p>\n

Building on this, Ganti and his colleagues figured out how to precisely calculate this lobe length under consistent flooding conditions in the lab. In addition to river depth and gradient, the scientists also considered factors such as the water\u2019s sediment load, the distance from lobe to shoreline, and the length of the transition zone from flowing river to relatively tranquil ocean waters. With this, the team was able to calculate where in their laboratory delta an avulsion was likely to occur.<\/p>\n

<\/a>

The current form of the Mississippi River delta is just one of many. Geomorphologists have identified at least six <\/a>other\u00a0historical lobes. Photo by\u00a0Universal Images Group North America LLC\/Alamy\u00a0Stock Photo<\/p><\/div>\n

If the research can be scaled up to the real world outside of the lab, the finding could be revolutionary. Hazard managers could calculate a river\u2019s potential avulsion point, monitor flooding and sedimentation, and issue evacuation warnings\u2014a windfall in a world where the global cost of flooding is expected to increase tenfold by 2030<\/a>.<\/p>\n

But determining where avulsions will occur is a small part of understanding the larger system, cautions Albert Kettner<\/a>, a hydrologist at the University of Colorado Boulder. \u201cHumans had, and still have, a significant impact on the morphology of deltas,\u201d he says, and these impacts\u2014agricultural practices, deforestation, and dams that starve deltas of sediment, for example\u2014skew the behavior of delta systems.<\/p>\n

There\u2019s another human impact muddying the waters, too: climate change. \u201cOne of the predictions of our model experiment is that if you have sea level rise, then future avulsions may actually occur farther upstream,\u201d says Ganti. This puts additional communities in jeopardy, and, according to Kettner, compounds the risks associated with highly modified waterways.<\/p>\n

Today, nearly 98 million people live in Shandong. The Yellow River\u2014shaped by human activity since the beginning<\/a>\u2014will avulse again, and researchers will have to account for these variables as they calculate avulsion timing. As delta cities grow, seas rise, and avulsions creep inland, it will only grow more essential that scientists keep an eye on the clock.<\/p>\n","protected":false},"excerpt":{"rendered":"

Some rivers naturally change course, often with little warning. Now scientists are learning how to predict their moves.<\/p>\n","protected":false},"featured_media":12706,"menu_order":0,"template":"","format":"standard","meta":{"_acf_changed":false,"om_disable_all_campaigns":false,"footnotes":""},"categories":[],"tags":[],"acf":{"hero_video_url":null,"hero_video_caption":"","deck":"Some rivers naturally change course, often with little warning. Now scientists are learning how to predict their moves.","authors_group":[{"by_group":"by","contributors_group":[15624]}],"word_count_override":"","podbean1":"","podbean2":"","redirect":"","geolocation":{"address":"38.942103, 119.62676","lat":38.942103,"lng":119.62676},"related":[16844,16821],"twitterimage":19044,"facebookimage":19043,"twitterdescription":"","edited":"","factchecked":"","code":"","no_old_story_flag":[]},"_links":{"self":[{"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/17133"}],"collection":[{"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/types\/custom_news"}],"version-history":[{"count":2,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/17133\/revisions"}],"predecessor-version":[{"id":20742,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/17133\/revisions\/20742"}],"acf:post":[{"embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/16821"},{"embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/news\/16844"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/media\/12706"}],"wp:attachment":[{"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/media?parent=17133"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/categories?post=17133"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hakaimagazine.com\/wp-json\/wp\/v2\/tags?post=17133"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}