Impact of a random sequence of debris flows on torrential fan formation

Bezak, Nejc (author), Sodnik, Jošt (author), Mikoš, Matjaž (author)

Debris flows with different magnitudes can have a large impact on debris fan characteristics such as height or slope. Moreover, knowledge about the impact of random sequences of debris flows of different magnitudes on debris fan properties is sparse in the literature and can be improved using numerical simulations of debris fan formation. Therefore, in this paper we present the results of numerical simulations wherein we investigated the impact of a random sequence of debris flows on torrential fan formation, where the total volume of transported debris was kept constant, but different rheological properties were used. Overall, 62 debris flow events with different magnitudes from 100 m$^3$ to 20,000 m$^3$ were selected, and the total volume was approximately 225,000 m$^3$. The sequence of these debris flows was randomly generated, and selected debris fan characteristics after the 62 events were compared. For modeling purposes, we applied the Rapid Mass Movement Simulations (RAMMS) software and its debris flow module (RAMMS-DF). The modeling was carried out using (a) real fan topography from an alpine environment (i.e., an actual debris fan in north-west (NW) Slovenia formed by the Suhelj torrent) and (b) an artificial surface with a constant slope. Several RAMMS model parameters were tested. The simulation results confirm that the random sequence of debris flow events has only some minor effects on the fan formation (e.g., slope, maximum height), even when changing debris flow rheological properties in a wide range. After the 62 events, independent of the selected sequence of debris flows, the final fan characteristics were not significantly different from each other. Mann Whitney (MW) tests and t-tests were used for this purpose, and the selected significance level was 0.05. Moreover, this conclusion applies for artificial and real terrain and for a wide range of tested RAMMS model rheological parameters. Further testing of the RAMMS-DF model in real situations is proposed in order to better understand its applicability and limitations under real conditions for debris flow hazard assessment or the planning of mitigation measures.

• Language: English
• Keywords: debris fans, RAMMS, numerical modelling, debris flow sequence, hazard assessment, Suhelj fan
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FGG - Faculty of Civil and Geodetic Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2019
• Number of pages: 14 str.
• Numbering: Vol. 9, iss. 2, art. 64
• PID: 20.500.12556/RUL-131996
• UDC: 556:004(479.4)
• ISSN on article: 2076-3263
• DOI: 10.3390/geosciences9020064
• COBISS.SI-ID: 8679265
• Publication date in RUL: 08.10.2021

Record is a part of a journal

• Title: Geosciences
• Shortened title: Geosciences
• Publisher: MDPI
• ISSN: 2076-3263
• COBISS.SI-ID: 519967769

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 01.02.2019

Secondary language

• Language: Slovenian
• Keywords: vršaj, RAMMS, numerično modeliranje, zaporedje drobirskih tokov, ocena ogroženosti, Suhelj, hidrologija

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: J7-8273
• Name: Prepoznavanje potencialno nevarnih hudourniških vršajev z metodami geomorfometrije in simulacijami nastanka vršajev

• Funder: Other - Other funder or multiple funders
• Funding programme: International Programme on Landslides
• Project number: IPL-225