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

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

Abstract

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 m3 to 20,000 m3 were selected, and the total volume was approximately 225,000 m3. 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.

Keywords

Vršaj;RAMMS;numerično modeliranje;zaporedje drobirskih tokov;ocena ogroženosti;Suhelj;hidrologija;debris fans;numerical modelling;debris flow sequence;hazard assessment;Suhelj fan;

Data

Language:	English
Year of publishing:	2019
Typology:	1.01 - Original Scientific Article
Organization:	UL FGG - Faculty of Civil and Geodetic Engineering
UDC:	556:004(479.4)
COBISS:	8679265
ISSN:	2076-3263
Views:	171
Downloads:	63
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	Slovenian
Secondary keywords:	vršaj;RAMMS;numerično modeliranje;zaporedje drobirskih tokov;ocena ogroženosti;Suhelj;hidrologija;
Type (COBISS):	Article
Pages:	str. 1-14
Volume:	ǂLetn. ǂ9
Issue:	ǂšt. ǂ2/64
Chronology:	2019
DOI:	10.3390/geosciences9020064
ID:	13675592