EGU2020-14843
https://doi.org/10.5194/egusphere-egu2020-14843
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Towards a probabilistic assessment of sediment yields in a mountainous area: the case study of Valle Camonica

Gian Battista Bischetti1,2, Paolo Sala1, Paolo Fogliata1, Emanuele Morlotti1, and Alessio Cislaghi1,2
Gian Battista Bischetti et al.
  • 1Department of Agricultural and Environmental Sciences (DiSAA), University of Milan, Milan, Italy (bischetti@unimi.it)
  • 2Centre of Applied Studies for the Sustainable Management and Protection of Mountain Areas (Ge.S.Di.Mont), University of Milan, Edolo (BS), Italy

Sediment production and delivery are hillslope processes characterized by significant variability and uncertainty, especially in mountain drainage catchments. Although sediments can be originated from several phenomena, such as slope instabilities, soil erosion and streambank failures, rainfall-induced landsliding, eventually turned into debris flows, is the dominant mechanism producing and conveying huge volumes of solid material to downstream areas through the channel network and therefore causing an increase of flood frequency.

Such landslide-derived mechanisms cause damage, directly and indirectly, to public and/or private properties and infrastructure on alluvial fans that are basically due to the increase of clogging probability of bridges, instream sediment accumulation, and significant geomorphological change. Identifying the sediment upstream source areas and quantifying a probability distribution of the mobilized- and delivered-sediment volume, then, is crucial for the protection of downstream areas. However, such purpose still remain extremely challenging because of scarcity, or even lack, of time-consuming direct measurements that are generally carried out at small scale and cover short time periods.

On this background, this work proposes a simplified procedure to estimate a probability distribution of the sediment yields combining: (i) rainfall intensity-duration-frequency (IDF) relationships for estimating synthetic precipitation with specific return time; (ii) a three-dimensional slope stability model to assess the rainfall-induced shallow landslides susceptibility; (iii) a connectivity index for mapping the probability of sediment delivery; and (iv) a simple hydrological model based on SCS-CN method to estimate the flood peak, and furthermore the probability distribution of sediment flux. The procedure requests low-resolution maps, usually available at the regional scale, such as digital elevation model, land cover, geology, lithology, and IDF curves, and represents a planning tool for climate and land cover change mitigation that can be extremely useful for forest managers, hydraulic engineering and watershed planners.

The procedure was tested on several small mountainous headwater catchments in Valle Camonica, located into the Central Italian Prealps, mostly covered by forests, with settlements on alluvial fans, and prone to shallow landslide, debris flood, and debris flow. It was qualitatively validated on the landslide inventory and the mapped flood areas, showing comparable results.

How to cite: Bischetti, G. B., Sala, P., Fogliata, P., Morlotti, E., and Cislaghi, A.: Towards a probabilistic assessment of sediment yields in a mountainous area: the case study of Valle Camonica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14843, https://doi.org/10.5194/egusphere-egu2020-14843, 2020

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Presentation version 1 – uploaded on 04 May 2020
  • AC1: Comment on EGU2020-14843, Alessio Cislaghi, 07 May 2020

    A note:

    In the present work, we combined empirical approaches and physical-based models. Both methods provide indicative assessments in terms of potential magnitude of extreme events, useful for a suitable catchment management. Some indexes, commonly used in practice, showed the range of magnitude of possible extreme events (e.g., debris-flows, shallow landslides), whereas physical-based models (and the connectivity index) can identify the portion of catchments in which there are a critical combination between a high landslide susceptibility and a high sediment connectivity, i.e. areas in which the local technicians have to concentrate thier monitoring and interventions. 

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    Here, some references:

    Cislaghi, A., Bischetti, G.B., 2019. Source areas, connectivity, and delivery rate of sediments in mountainous-forested hillslopes: A probabilistic approach. Science of The Total Environment 652, 1168–1186.
    Cislaghi, A., Rigon, E., Lenzi, M.A., Bischetti, G.B., 2018. A probabilistic multidimensional approach to quantify large wood recruitment from hillslopes in mountainous-forested catchments. Geomorphology 306, 108–127.
    Cavalli, M., Trevisani, S., Comiti, F., Marchi, L., 2013. Geomorphometric assessment of spatial sediment connectivity in small Alpine catchments. Geomorphology 188, 31–41.
    Persichillo, M.G., Bordoni, M., Cavalli, M., Crema, S., Meisina, C., 2018. The role of human activities on sediment connectivity of shallow landslides. CATENA 160, 261–274.