Effect assessment of debris flow mitigation works based on numerical simulation by using Kanako 2D

Abstract

Mitigation works are very essential for mitigation of debris-flow hazards in mountainous areas. Usually, it is difficult to assess the effectiveness of existing mitigation works in a catchment. This paper presented a method for quantitative assessment of debris flow mitigation measures by using Kanako system, a user-friendly GUI-equipped debris flow simulator that allows good visualization and easy interpretation. Kanako 2D (Ver. 2.04) was applied to a case study at Caijia Gully, Sichuan Province, China. Mitigation works including check dams, drainage channel, and deposition basin were constructed in the gully in 2001 and 2006. Kanako 2D can simulate debris flow from steep area to alluvial fan. 1D simulation was applied for assessing the effect of the check dams at the lower part of the gully, and 2D simulation was applied for the effect of the drainage channel and deposition basin on the alluvial fan. The simulation results indicate that debris flow will cause great damage to residential area on the alluvial fan if mitigation measures were not implemented in the gully. For old dams which have been filled up with deposits of previous debris flows, the results show that they still have the function for controlling debris flow due to the gradient reduction of the channel bed in front of the dams by the trapped debris flow deposition. After the comprehensive control of debris flow including trapping, drainage, and deposition in the gully, the simulation results indicate that the risk on the alluvial fan can be reduced to an acceptable level.

Dynamic Process Analysis and Hazard Prediction of Debris Flow in Eastern Qinghai-Tibet Plateau Area—A Case Study at Ridi Gully

“…In this analysis, some empirical equations (such as Equations [12] and [21]) were applied to calculate debris-flow dynamic parameters. Although these equations were often used in previous studies (You et al, 2010;Liu et al, 2012;Xiang et al, 2012;Cui et al, 2013), more accurate tests are necessary to further improve the precision of these empirical equations as well as to develop better theoretical models. For instance, the debris-flow density calculation (Equation [12]) was established based on over 100 tests and in- vestigated data sets; however, there exists an opportunity for improvement by replacing the current polynomial equation with a theoretical model based on dimensional analysis.…”

“…The parameter F can be directly calculated and measured from the topographic map by using GIS technology. S, T, ϕ, and n can be determined by the following empirical equations (Liu et al, 2012):…”

An experimental study of dilute debris flow characteristics in a drainage channel with an energy dissipation structure

“…Debris flow mitigation measures can be classified as structural or nonstructural. Structural measures include check dams (Armanini and Larcher, 2001;Chanson, 2004;Hassanli et al, 2009), drainage systems (Takahisa, 2008;You et al, 2011), flexible barriers (Canelli et al, 2012), and debris flow basins (Ikeya, 1989;Liu et al, 2013), whereas nonstructural measures include warning and evacuation systems, appropriate land use, and retrofitting of buildings (Navratil et al, 2013;Okano et al, 2012). After the Wenchuan earthquake, a large number of debris flows occurred in gullies that had never experienced a debris flow disaster before the earthquake (the number of new debris flow gullies increased more than 1000-fold).…”

Assessing entrainment of bed material in a debris‐flow event: a theoretical approach incorporating Monte Carlo method

“…Several models have been developed and applied for this purpose (e.g. Brufau et al, 2000;Imran et al, 2001;Hungr et al, 2005;Mangeney et al, 2007;Bouchut et al, 2008;Medina et al, 2008;Wang et al, 2008;Beguería et al, 2009;Crosta et al, 2009aCrosta et al, , 2009bLin et al, 2009;Pirulli and Pastor, 2012;Liu et al, 2013;Han et al, 2015a). These models are mainly physically based and numerically solved.…”