Applications of simulation technique on debris-flow hazard zone delineation: a case study in Hualien County, Taiwan

Abstract

Abstract. Debris flows pose severe hazards to communities in mountainous areas, often resulting in the loss of life and property. Helping debris-flow-prone communities delineate potential hazard zones provides local authorities with useful information for developing emergency plans and disaster management policies. In 2003, the Soil and Water Conservation Bureau of Taiwan proposed an empirical model to delineate hazard zones for all creeks (1420 in total) with potential of debris flows and utilized the model to help establish a hazard prevention system. However, the model does not fully consider hydrologic and physiographical conditions for a given creek in simulation. The objective of this study is to propose new approaches that can improve hazard zone delineation accuracy and simulate hazard zones in response to different rainfall intensity. In this study, a two-dimensional commercial model FLO-2D, physically based and taking into account the momentum and energy conservation of flow, was used to simulate debris-flow inundated areas.Sensitivity analysis with the model was conducted to determine the main influence parameters which affect debris flow simulation. Results indicate that the roughness coefficient, yield stress and volumetric sediment concentration dominate the computed results. To improve accuracy of the model, the study examined the performance of the rainfallrunoff model of FLO-2D as compared with that of the HSPF (Hydrological Simulation Program Fortran) model, and then the proper values of the significant parameters were evaluated through the calibration process. Results reveal that the HSPF model has a better performance than the FLO-2D model at peak flow and flow recession period, and the volumetric sediment concentration and yield stress can be estimated by the channel slope. The validation of the model for Correspondence to: S. M. Hsu (shihmeng@sinotech.org.tw) simulating debris-flow hazard zones has been confirmed by a comparison of field evidence from historical debris-flow disaster data. The model can successfully replicate the influence zone of the debris-flow disaster event with an acceptable error and demonstrate a better result than the empirical model adopted by the Soil and Water Conservation Bureau of Taiwan.

The use of FLO2D numerical code in lahar hazard evaluation at Popocatépetl volcano: a 2001 lahar scenario

“…Analysis of the different input parameters was performed by Boniello et al (2010), Hsu et al (2010), and Worni et al (2012). They include data from the FLO2D user's manual, as well as back analysis to fit field and debris flow data from the literature in order to obtain confident rheological coefficients.…”

Evaluation concepts to compare observed and simulated deposition areas of mass movements

“…For both approaches, an error value of d = 0, respectively q = 1 does not only refer to a perfect fit but can theoretically also imply no overlapping for areas with equal magnitudes. To avoid this problem [19,24,43,53] used the amount of overlap between reference and simulation as a measure of accuracy. Their error-approach can be defined as q = X/A.…”

The 27 May 1937 catastrophic flow failure of gold tailings at Tlalpujahua, Michoacán, Mexico

“…The resistive component involves different shear stress (cohesive, viscous, turbulent, and dispersive) and the MohrCoulomb shear. The model was previously tested for different sediment-laden flows, such as debris flow (Sosio et al, 2007;Boniello et al, 2010;Hsu et al, 2010), lahars (Worni et al, 2012, Caballero et al, 2014, and debris flow from dam breach (Li et al, 2011). The quadratic rheological model requires two pairs of user-defined rheological coefficients (α and β) for viscosity and yields stress as a function of the sediment concentration by volume (Cv).…”