Abstract:The proper assessment of design flood is a major concern for many hydrological applications in small urban watersheds. A number of approaches can be used including statistical approach and the continuous simulation and design storm methods. However, each method has its own limitations and assumptions being applied to the real world. The design storm method has been widely used for a long time because of the simplicity of the method, but three critical assumptions are made such as the equality of the return periods between the rainfall and corresponding flood quantiles and the selections of the rainfall hyetograph and antecedent soil moisture conditions. Continuous simulation cannot be applied to small urban catchments with quick responses of runoff to rainfall. In this paper, a new flood frequency analysis for the simulated annual peak flows (FASAP) is proposed. This method employs the candidate rainfall events selected by considering a time step order of five minutes and a sliding duration without any assumptions about the conventional design storm method in an urban watershed. In addition, the proposed methodology was verified by comparing the results with the conventional method in a real urban watershed. OPEN ACCESSWater 2014, 6 3842 Keywords: design storm method; continuous simulation method; flood frequency analysis; urban drainage basin

This paper deals with a numerical investigation of incident wave interactions with a moored pontoon-type floating breakwater. The element-free Galerkin method, in which only nodal data are required to analyze the problem, is employed to solve the diffraction and radiation boundary value problems addressed by the modified Helmholtz equation. The numerical model includes the hydrodynamic and mooring analyses, and it is validated by previous numerical and experimental results. Using the numerical model, we are able to assess the hydrodynamic performance of a moored pontoon-type floating breakwater in regular waves. Numerical results are presented to show the effects of wave conditions and mooring system configuration. This paper also presents the simple forms of stiffness coefficients of a slack mooring line. The influence of mooring line condition on the performance of a floating breakwater is highlighted.Résumé : Cet article présente une étude numérique des interactions des ondes incidentes sur un brise-lames flottant amarré de type ponton. La méthode sans maillage de Galerkin, dans laquelle uniquement les données nodales sont requises pour analyser le problème, est employée pour résoudre les problèmes de valeur de diffraction et de rayonnement aux limites tels qu'abordés par l'équation d'Helmholtz modifiée. Le modèle numérique comprend les analyses hydrodynamiques et d'amarrage et il est validé par les résultats numériques et expérimentaux antérieurs. En utilisant le modèle numérique, nous pouvons évaluer la performance hydrodynamique d'un brise-lames flottant amarré de type ponton avec des conditions de vagues régulières. Les résultats numériques sont présentés afin de montrer les effets des conditions de vagues et de la configuration d'amarrage. Cet article présente également les formes simples des coefficients de rigidité d'une ligne d'amarrage à tension variable. L'influence de l'état de la ligne d'amarrage sur le rendement d'un brise-lames flottant est soulignée.Mots clés : brise-lames flottant amarré, méthode sans maillage de Galerkin, condition de la ligne d'amarre.[Traduit par la Rédaction]

This study develops a full Bayesian GEV distribution estimation method (BAYBETA), which contains a semi-Bayesian framework of generalized maximum likelihood estimator (GMLE), to make full use of several advantages of the Bayesian approach especially in uncertainty analysis. For the full Bayesian framework, the optimal hyperparameter of beta prior distribution on the shape parameter of the GEV distribution is found as (6.4990, 8.7927) through simulation-based analysis. In a performance comparison analysis, the performances of BAYBETA, which adopts beta(6.4990, 8.7927) as prior density on the shape parameter of the GEV distribution, are almost the same as or slightly better than GML, outperforming MOM, ML, and LM in terms of root mean square error (RMSE) and bias when the shape parameter is negative. Also, a case study of two hydrologic extreme value data shows that the traditional uncertainty analysis using asymptotic approximation of ML and GML has limitations in describing the uncertainty in high upper quantiles, while the proposed full Bayesian estimation method BAYBETA provides a consistent and complete description of the uncertainty.

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The orographic effect is a common phenomenon in mountainous regions. Our goal is to analyze the orographic effect with quantile by regional frequency analysis and multiple regression. Multiple regression was used to develop models to estimate the amount and the spatial distribution of orographic precipitation in mountainous terrain using elevation, latitude, longitude, duration, and return period. Multiple linear regression analysis indicated that the model using the three parameters of elevation, latitude, and longitude, produces better results than fouror five-parameter models. Therefore, multiple nonlinear forms, the combination of the intensity-duration-frequency (IDF) relationship and the general linear regression form of orographic statistics were proposed to improve the accuracy of models. The models in this study showed an increase in accuracy of 18.31∼86.27%. Moreover, these models produced good results in GIS analysis and were able to represent all cases examined in this study using only a few equations, in contrast to multiple linear models.

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