{"id":612,"date":"2013-09-26T14:04:23","date_gmt":"2013-09-26T12:04:23","guid":{"rendered":"http:\/\/wp.unil.ch\/risk\/?p=612"},"modified":"2013-10-31T11:06:20","modified_gmt":"2013-10-31T10:06:20","slug":"benjamin-rudaz-evolution-geomorphodynamique-dun-bassin-versant-torrentiel","status":"publish","type":"post","link":"https:\/\/wp.unil.ch\/risk\/benjamin-rudaz-evolution-geomorphodynamique-dun-bassin-versant-torrentiel\/","title":{"rendered":"Benjamin Rudaz: Evolution G\u00e9omorphodynamique d\u2019un bassin versant torrentiel"},"content":{"rendered":"<p><em>Benjamin Rudaz<\/em><br \/>\n<em>Supervisor: Prof. Michel Jaboyedoff<\/em><br \/>\n<em>Expert: Alexandre Loye<\/em><\/p>\n<p style=\"text-align: justify\">This master thesis is focused on the Saint-Barth\u00e9l\u00e9my stream, in the canton of Valais, Switzerland.\u00a0It drains a catchment cut in three different geological units forming the Dents du Midi massif. Its\u00a0massive torrential fan fills the whole width of the Rh\u00f4ne Valley.<\/p>\n<p style=\"text-align: justify\">Historically, the Saint-Barth\u00e9l\u00e9my has on numerous occasions affected the human activities in\u00a0the region, by cutting communications, damming the Rh\u00f4ne river, or simply by overflowing its\u00a0banks on the debris cone. Thus, this work starts with a historical reconstitution of its past activities,\u00a0with the goal of finding a pattern. The best documented crisis happened between 1926 and 1930.\u00a0The different crisis recorded are mainly caused by rock avalanches in the upper part of the catchment.\u00a0They result in a huge sediment supply, in a steep and snow-filled gorge. Debris flows initiate\u00a0there, amplify in volume in the middle-part of the catchment, and reach the alluvial fan in multiple\u00a0waves. To stabilize the terrain, and thus avoid future debris flows, the 1930 crisis was followed by\u00a0an intense correction campaign. The different dams are hereby described, and their current status\u00a0is evaluated.<\/p>\n<p style=\"text-align: justify\">The steady-state regime theory, applied on longitudinal profiles, states that for a stream to be\u00a0in such state, its long profile must be upward concave, and follow a mathematical form, be it exponential,\u00a0logarithmic or that of a power law. The streams present in the catchment are evaluated\u00a0on this basis, using theorical longitudinal profile, of the exponential type. Their concavity is calculated,\u00a0thus giving information about the maturity of said profiles. The longitudinal profiles are\u00a0compared in their normalized form. The results identify a global pattern of potential sedimentation\u00a0at the center of the catchment, while the external parts are expected to erode. The desequilibrium\u00a0is stronger in the northern lateral streams.<\/p>\n<p style=\"text-align: justify\">A longitudinal profile in steady-state regime should be smooth. Therefore, profile irregularities,\u00a0or knickpoints, are another sign of unsteady regime. To identify those knickpoints, three methods\u00a0are used. First, using normalized profiles, the knickpoints are subjectively identified. Two numerical\u00a0methods are then used to detect brutal change of local slope, relative to the neighbouring\u00a0segments. The results show more precisely where future erosion is expected. The upper Saint-Barth\u00e9l\u00e9my stream is particularly disturbed. The knickpoints are finally caracterized between geological,\u00a0geomorphological and human origin.<\/p>\n<p style=\"text-align: justify\">By orthorectifying aerial photographs dating between 1969 et 1992, the activity of landslides\u00a0connected to the main stream is measured. Lastly, using a sloping local base level method, the\u00a0volume trapped behind the check dams is calculated, allowing to estimate mechanical denudation\u00a0rates for different time frames. These rates (0.14 up to 0.84 mm\/year) are in the range of similarly\u00a0obtained rates in the Swiss Alps.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Benjamin Rudaz Supervisor: Prof. Michel Jaboyedoff Expert: Alexandre Loye This master thesis is focused on the Saint-Barth\u00e9l\u00e9my stream, in the canton of Valais, Switzerland.\u00a0It drains a catchment cut in three &hellip; <\/p>\n","protected":false},"author":1341,"featured_media":1140,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","ngg_post_thumbnail":0,"footnotes":""},"categories":[73758],"tags":[302],"class_list":{"0":"post-612","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-masters_completed","8":"tag-302"},"_links":{"self":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts\/612","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/users\/1341"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/comments?post=612"}],"version-history":[{"count":0,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/posts\/612\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/media\/1140"}],"wp:attachment":[{"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/media?parent=612"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/categories?post=612"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wp.unil.ch\/risk\/wp-json\/wp\/v2\/tags?post=612"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}