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In this paper, based on the concepts of uncertainty and reliability analyses, a method used for assessment of risk due to debris flow events is proposed. First, procedures for obtaining the configuration of debris-flow fans are presented. Then, the parameters affecting the configuration of debris-flow fans are identified and their corresponding means and standard deviations are derived. Finally, the proposed method is applied to the Shih-Pa-Chung Creek in central Taiwan. The expected deposition thickness at any point in the deposition area is computed and then the contours of risk for the 50-year and 100-year events are constructed. Regarding the expected deposition thickness, it is found that the closer the distance from the canyon mouth, the larger the debris-flow thickness becomes. The results also show that the contours of risk are of the shape of an ellipse similar to the shape of deposition area, and the risk at a point decreases with increasing distance of that point from the canyon mouth. In addition, when the return period of rainfall event is fixed, the variation in risk decreases as the distance from the canyon mouth increases. For the assessment of risk due to debris flow events, the proposed method is recommended as an alternative to the existing methods, because the influence of all the uncertainty of the parameters is considered.

Coastal and riparian flooding are costly and disruptive natural hazards and already a regular part of life in some areas of the USA. Flooding events caused by sea-level rise and climate change are expected to increase in frequency and severity in the future, creating social, ecological, and economic problems at local, city, state, and federal levels. It is clear that normative, infrastructure-oriented, and strictly hydrological solutions to flooding have not appropriately met these challenges, nor have they adequately addressed relevant socio-political factors which shape hydrological processes. Using the case study of Tillamook County, this study draws upon qualitative interview data to identify and explain social factors which have influenced the outcome of a collaborative, socially engaged flood management project. These include previous flood experience; emotions and feelings; interests and concerns; preferred management strategies; barriers to community-scientific engagement; and perceptions of a mediation process. This situation is further explored within the framework of social geometry, which is used to explain changes in social position and relationships through an interactive, collaborative process. In this case, mediation is shown to decrease both relational space and differences in status between the two primary actor groups, leading to mutually agreeable outcomes but not without dispute. Flood managers and researchers may find this case study useful when analyzing qualitative data related to flood risk management, and/or planning flood management strategies, particularly in disaster-prone regions.

In the recent times, several advanced numerical models are utilized for the prediction of the intensity, track and landfall time of a cyclone. Still there are number of issues concerning their prediction and the limitation of numerical models in addressing those issues. The most pertinent question is how intensive a cyclone can become before it makes a landfall and where the cyclone moves under the ambient large-scale flow. In this paper, detailed study has been carried out using Weather Research Forecast model with two boundary schemes to address the above question by considering a recent tropical cyclone in Bay of Bengal region of North Indian Ocean. In addition, the impact of the surface drag effect on the low-level winds and the intensity of the cyclone are also studied. The result reveals that large differences are noted in the ocean surface fluxes between YSU and MYJ with MYJ producing relatively higher fluxes than YSU. It is found that the YSU scheme produced a better simulation for the THANE cyclone in terms of winds, pressure distribution and cloud fractions. Comparison with available observations indicated the characteristics of horizontal divergence, vorticity and vector track positions produced by YSU experiment are more realistic than with MYJ and other experiments. However, when the drag coefficient is changed as 0.5 or 2.0 from the default values, appreciable changes in the surface fluxes are not noticed. A maximum precipitation is reported in YSU as compared to the MYJ PBL scheme for the tropical cyclone THANE.

A 3-D large eddy simulation model that was first transformed to smoothed particle hydrodynamics (LES-SPH)-based model was employed to study breaking tsunami waves in this paper. LES-SPH is a gridless (or mesh-free), purely Lagrangian particle approach which is capable of tracking the free surface of violent deformation with fragmentation in an easy and accurate way. The Smagorinsky closure model is used to simulate the turbulence due to its simplicity and effectiveness. The Sub-Particle Scale scheme, plus the link-list algorithm, is applied to reduce the demand of computational power. The computational results show that the 3-D LES-SPH model can capture well the breaking wave characteristics. Spatial evolution features of breaking wave are presented and visualized. The detailed mechanisms of turbulence transport and vorticity dynamics are demonstrated as well. This application also presents an example to validate the SPH model.