International Journal of Erosion Control Engineering
Online ISSN : 1882-6547
ISSN-L : 1882-6547
Volume 9 , Issue 2
Showing 1-4 articles out of 4 articles from the selected issue
Original Article
  • Rosiret ESCALONA, Atsuhiro YOROZUYA, Shinji EGASHIRA, Yoichi IWAMI
    Type: Original Article
    2016 Volume 9 Issue 2 Pages 25-31
    Published: June 24, 2016
    Released: June 24, 2016
    JOURNALS FREE ACCESS
    To analyze the fan formation process due to swing phenomena of the debris flow, the authors performed a numerical simulation of debris flow by means of depth integrated two dimensional governing equations of solid-water mixture and the bed shear stress formula characterized by yield and the fluid type shear stress. In this research, the debris flow phenomena and fan formation processes are studied as the test case applied in the Chacaito Creek located in the metropolitan urban area of Caracas city, Venezuela. The results of 2-D numerical simulations confirmed the influences of swing phenomena in the temporal variations of the morphology of debris fan. Likewise, the research demonstrates that fan formation processes in successive numerical simulations have variations in the spatial distribution of the sediment deposition due to changes in the debris flow directions caused by the topographic conditions at the fan head and the swing phenomena.
    Download PDF (1457K)
  • Li-Jeng HUANG
    Type: Original Article
    2016 Volume 9 Issue 2 Pages 32-42
    Published: June 24, 2016
    Released: June 24, 2016
    JOURNALS FREE ACCESS
    This paper presents the fuzzy analytic hierarchy process (FAHP) for risk assessment of debris-flow occurrence using three different fuzzy numbers. Three layers are involved in the structure of the FAHP: the goal layer, the criteria layer, and the sub-criteria layer. In the criteria and sub-criteria layers, nine major influence factors are grouped into three categories: (1) topological and geological conditions, which includes the influence factors of slope angle, type of deposit, grain size distribution, and surface plants; (2) watershed conditions, which includes effective watershed area and quantity of outflow of sediment; and (3) rainfall conditions, which includes rainfall intensity, duration, and accumulated rainfall. Judgment regarding the relative influence of these factors is based on a nine-level scale used to form the fuzzy reciprocal judgment matrices for evaluating the weighting vectors for each layer. Two cases of debris-flow disasters that occurred in eastern Taiwan were tested using the FAHP; one was a debris flow, and the other a mudslide. The results showed that the proposed FAHP models using the three kinds of fuzzy numbers as well as the associated influence factors and criteria can successfully predict the risk of debris-flow hazard occurrence. Furthermore, the predicted overall risk indices obtained from the FAHP using the three kinds of fuzzy numbers were smaller than those obtained from AHP, but more practical due to consideration of the uncertainty and vagueness involved in natural hazards.
    Download PDF (450K)
  • Go YANAGISAKI, Masashi AONO, Hironori TAKENAKA, Masayuki TAMAMURA, Kan ...
    Type: Original Article
    2016 Volume 9 Issue 2 Pages 43-57
    Published: June 24, 2016
    Released: June 24, 2016
    JOURNALS FREE ACCESS
    Large-scale sediment-related disasters have been increasing in recent years [Uchida et al., 2009; Inoue and Doshida, 2012], such as the deep-seated catastrophic landslides caused by Typhoon Talas (T1112) in the Kii Peninsula, southwest Japan, in 2012. The formation and collapse processes of landslide dams strongly influence water and sediment runoff. When a large-scale landslide dam collapses, the peak discharge of downstream flooding can sometimes become several times as large as the inflow discharge upstream. Such abrupt increases in flow discharge often cause serious disasters in downstream areas. The objective of this study was to support prediction systems for hazards caused by debris flows. We developed a crisis management system to contribute to evacuation decisions and actions by providing information to residents. We adopted Hyper KANAKO as the basic tool of the crisis management system. This system can also provide results of temporal changes such as flow depth and sedimentation depth for the administrator. The time-series images are associated with a world file that responds to geographic information from a 2D topographic model. It is possible to check the simulation results on a GIS as soon as calculations have been performed. In addition to the existing system, we developed functions to reproduce the side-bank erosion caused by landslide dam overtopping. This new system requires setting the height of the landslide dam, the width of the river channel, the initial overflow channel width of the landslide dam, and the numerical constant for side-bank erosion velocity as calculation conditions. The system can display the widening of the overflow channel of the landslide dam caused by overtopping, and analyze a series of phenomena related to flooding from the overtopping erosion of the landslide dam. Moreover this system can assist in developing more effective countermeasures and hazard maps for disaster mitigation.
    Download PDF (2187K)
Technical Note
  • Yeon-Joong KIM, Kohji TANAKA, Hideaki NAKASHIMA, Eiichi NAKAKITA
    Type: Technical Note
    2016 Volume 9 Issue 2 Pages 58-67
    Published: June 24, 2016
    Released: June 24, 2016
    JOURNALS FREE ACCESS
    Large-scale sediment-related disasters have been increasing in recent years [Uchida et al., 2009; Inoue and Doshida, 2012], such as the deep-seated catastrophic landslides caused by Typhoon Talas (T1112) in the Kii Peninsula, southwest Japan, in 2012. The formation and collapse processes of landslide dams strongly influence water and sediment runoff. When a large-scale landslide dam collapses, the peak discharge of downstream flooding can sometimes become several times as large as the inflow discharge upstream. Such abrupt increases in flow discharge often cause serious disasters in downstream areas. The objective of this study was to support prediction systems for hazards caused by debris flows. We developed a crisis management system to contribute to evacuation decisions and actions by providing information to residents. We adopted Hyper KANAKO as the basic tool of the crisis management system. This system can also provide results of temporal changes such as flow depth and sedimentation depth for the administrator. The time-series images are associated with a world file that responds to geographic information from a 2D topographic model. It is possible to check the simulation results on a GIS as soon as calculations have been performed. In addition to the existing system, we developed functions to reproduce the side-bank erosion caused by landslide dam overtopping. This new system requires setting the height of the landslide dam, the width of the river channel, the initial overflow channel width of the landslide dam, and the numerical constant for side-bank erosion velocity as calculation conditions. The system can display the widening of the overflow channel of the landslide dam caused by overtopping, and analyze a series of phenomena related to flooding from the overtopping erosion of the landslide dam. Moreover this system can assist in developing more effective countermeasures and hazard maps for disaster mitigation.
    Download PDF (1720K)
feedback
Top