Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 10 3 2010 10.5194/nhess-10-535-2010 http://www.nat-hazards-earth-syst-sci.net/10/535/2010/ http://www.nat-hazards-earth-syst-sci.net/10/535/2010/nhess-10-535-2010.html http://www.nat-hazards-earth-syst-sci.net/10/535/2010/nhess-10-535-2010.pdf 535 545 2010-03-23 Applications of simulation technique on debris-flow hazard zone delineation: a case study in Hualien County, Taiwan S. M. Hsu shihmeng@sinotech.org.tw L. B. Chiou G. F. Lin C. H. Chao H. Y. Wen C. Y. Ku Geotechnical Engineering Research Center, Sinotech Engineering Consultants, Inc., Taipei, Taiwan Department of Civil engineering, National Taiwan University, Taipei, Taiwan Department of Harbour and River Engineering, National Taiwan Ocean University, Keelung, Taiwan 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. <br><br> 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 rainfall-runoff 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. 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