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Geomorphological mapping in high mountain watersheds : the contribution of geomorphology to the evaluation of sediment transfer processes

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  • Earth Science
  • Engineering
  • Geography
  • Law


Polarne vol. 5 druk.vp We will present the first results of a PhD thesis carried out at the Institute of Geography of Lausanne University (IGUL, under the supervision of Prof. Emmanuel Reynard) and with the collabora- tion of the Roads and Watercourse Service and the Forests and Landscape Service of the canton of Valais, Switzerland. Introduction A huge range of geomorphological legend sys- tems have been developed since the sixties all over the world and currently, geomorphologic mapping is one of the main research interests of the Institute of Geography at the University of Lausanne (IGUL) that has developed its own legend, based on various European legend systems (Schoeneich et al. 1998). The legend represents landforms by their genesis more than by their dynamics and has been used in the Swiss Alps for twenty years. In fact, the IGUL legend is mostly used for inventories and the man- agement of landforms or landscape protection and it is insufficient to appreciate dynamic processes like debris flows. Problematic After severe floods in Switzerland in 1987, the Swiss federal laws and ordinances on river engineer- ing and forests impose the responsibility of establish- ing hydrological hazard maps, which should become an obligatory tool for land planning. The method ap- plied by the federal authorities consists of three steps: the first one consists in establishing a “phe- nomena” map produced by using field geomorphological evidence (Kienholz, Krummen- acher 1995) ; then, based on this evidence, intensity maps are produced, either by numerical modelling and/or expert-system mapping; the last step, called hazard map, is a much more synthetic map, which shows the different degrees of danger and is based on two main parameters: intensity and probability of hazard. The hazard map allows the representation of five degrees of danger. This methodology is also used for snow avalanche and rockfall danger. The variety of tools available leads to some inconsistencies in the field. In fact

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