Spatial variability and potential impacts of climate change on flood and debris flow hazard zone mapping and implications for risk management

Abstract. The main goals of this study were to identify the alpine torrent catchments that are sensitive to climatic changes and to assess the robustness of the methods for the elaboration of flood and debris flow hazard zone maps to specific effects of climate changes. In this study, a procedure for the identification and localization of torrent catchments in which the climate scenarios will modify the hazard situation was developed. In two case studies, the impacts of a potential increase of precipitation intensities to the delimited hazard zones were studied. The identification and localization of the torrent and river catchments, where unfavourable changes in the hazard situation occur, could eliminate speculative and unnecessary measures against the impacts of climate changes like a general enlargement of hazard zones or a general over dimensioning of protection structures for the whole territory. The results showed a high spatial variability of the sensitivity of catchments to climate changes. In sensitive catchments, the sediment management in alpine torrents will meet future challenges due to a higher rate for sediment removal from retention basins. The case studies showed a remarkable increase of the areas affected by floods and debris flow when considering possible future precipitation intensities in hazard mapping. But, the calculated increase in extent of future hazard zones lay within the uncertainty of the methods used today for the delimitation of the hazard zones. Thus, the consideration of the uncertainties laying in the methods for the elaboration of hazard zone maps in the torrent and river catchments sensitive to climate changes would provide a useful instrument for the consideration of potential future climate conditions. The study demonstrated that weak points in protection structures in future will become more important in risk management activities.

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

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-535-2010 ◽

2010 ◽

Vol 10 (3) ◽

pp. 535-545 ◽

Cited By ~ 37

Author(s):

S. M. Hsu ◽

L. B. Chiou ◽

G. F. Lin ◽

C. H. Chao ◽

H. Y. Wen ◽

...

Keyword(s):

Debris Flow ◽

Yield Stress ◽

Empirical Model ◽

Water Conservation ◽

Debris Flows ◽

Sediment Concentration ◽

Hazard Zone ◽

Debris Flow Hazard ◽

Debris Flow Disaster ◽

Soil And Water

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 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. The validation of the model for 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.

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Mapping Debris Flow Hazard Zone at Mudan Reservoir Watershed in Taiwan

10.13031/2013.4822 ◽

2013 ◽

Author(s):

Sheng Liang

Keyword(s):

Debris Flow ◽

Hazard Zone ◽

Reservoir Watershed ◽

Debris Flow Hazard

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Debris flow hazard mapping considering the effect of mitigation structure – a case study in Taiwan based on numerical simulation

10.5194/egusphere-egu2020-6686 ◽

2020 ◽

Author(s):

Chih-Hao Hsu ◽

Chuan-Yi Huang ◽

Ting-Chi Tsao ◽

Hsiao-Yuan Yin ◽

Hsiao-Yu Huang ◽

...

Keyword(s):

Debris Flow ◽

Water Conservation ◽

Large Scale ◽

Mass Movement ◽

Hazard Mapping ◽

Hazard Map ◽

Inundation Depth ◽

Central Taiwan ◽

Debris Flow Hazard ◽

Typhoon Herb

This study added the dams and retain basin according to their dimensions measured with UAV onto the original 5m-resolition DEM to compare the effect of mitigation structures to debris flow hazard. The original and the modified DEMs were both applied to simulate the consequences by using RAMMS::Debris Flow (RApid Mass Movement Simulation) model.Hazard map is the best tool to provide the information of debris flow hazard in Taiwan. It has an important role to play in evacuating the residents within the affected zone during typhoon season. For the reason, debris flow hazard maps become a useful tool for local government to execute the evacuation. As the mitigation structure is constructed, the intensity of debris flow hazard reduces.The Nantou DF190 debris flow potential torrent is located in central Taiwan. In 1996 when Typhoon Herb stroke, 470,000 cubic-meter of debris were washed out and deposited in 91,200 square-meter area (Yu et al., 2006), and the event caused the destruction of 10 residential houses with 2 fatalities. After the event the Soil and Water Conservation Bureau constructed a 100-meter long sabo dam and sediment retain basin with capacity of 60,000 cubic-meters. In order to compare the difference of affected zone before and after the construction of mitigation structures, the study applies RAMMS to simulate the above-mentioned event.The result shows when large-scale debris flow occurs, most of the sediments still overflow and deposit on the fan with shape similar to the 1996 Typhoon Herb event. However, the intensity has reduced significantly with 50% less in area, several meters less in inundation depth and 50% less in flow velocity approximately. The comparison shows the effect of mitigation structures and could provide valuable information for debris flow hazard mapping.Key Words: Debris flow, RAMMS, Hazard map, Mitigation, Taiwan

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Debris flow hazard mapping with a random walk model in Korea

Risk Analysis VII ◽

10.2495/risk100521 ◽

2010 ◽

Author(s):

H.-J. Youn ◽

C.-W. Lee ◽

C.-S. Woo

Keyword(s):

Random Walk ◽

Debris Flow ◽

Random Walk Model ◽

Hazard Mapping ◽

Debris Flow Hazard

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Combining TRIGRS and DEBRIS-2D Models for the Simulation of a Rainfall Infiltration Induced Shallow Landslide and Subsequent Debris Flow

Water ◽

10.3390/w11050890 ◽

2019 ◽

Vol 11 (5) ◽

pp. 890 ◽

Cited By ~ 2

Author(s):

Yu-Charn Hsu ◽

Ko-Fei Liu

Keyword(s):

Debris Flow ◽

Depth Distribution ◽

Shallow Landslide ◽

Rainfall Infiltration ◽

The Real ◽

Hazard Zone ◽

Before And After ◽

Flow Motion ◽

Debris Flow Hazard ◽

Area And Volume

TRIGRS revealed the responses of the total pressure heads and factors of safety with a depth change under a rainfall infiltration occurring on the Daniao tribe’s hill. The depth distribution of the collapsed zone could be identified under the condition where the factors of safety Fs = 1, and the results could calculate the area and volume. Afterward, DEBRIS-2D used TRIGRS’s results to assess the hazard zone of the subsequent debris flow motion. In this study, the DTM variation analysis results from both of before and after the Daniao tribe’s landslide are used to validate TRIGRS’s simulation, the area and the volume of the collapse zone within 8% and 23% errors, respectively. The real disaster range was depicted from the aerial photo used to validate the hazard zone simulation of DEBRIS-2D within 25% errors. In spite of that, the hazard zone from the simulation still included the real disaster range. The combining method for a rainfall infiltration induced a shallow landslide and subsequent debris flow, which was well-matched on a real disaster range on the Daniao tribe’s hill. Therefore, we believe that the TRIGRS and DEBRIS-2D combining methods would provide a better solution for an assessment of a rainfall infiltration inducing shallow landslide and subsequent debris flow motion. TRIGRS could, therefore, provide the area and depth distribution of the collapsed zone, and DEBRIS-2D could use TRIGRS’s results for subsequent debris flow hazard assessment. Furthermore, these results would be of great help in the management of slope disaster prevention.

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