Regional Frequency Analysis of Extreme Rainfalls in the West Coast of Peninsular Malaysia using Partial L-Moments
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Regional Frequency Analysis of Extreme Rainfalls in the West Coast of Peninsular Malaysia using Partial L-Moments Zahrahtul Amani Zakaria & Ani Shabri & Ummi Nadiah Ahmad
Received: 4 August 2011 / Accepted: 17 September 2012 / Published online: 6 October 2012 # Springer Science+Business Media Dordrecht 2012
Abstract This study was to reinstate the development of regional frequency analysis using L-moments approach. The Partial L-moments (PL-moments) method was employed and a new relationship for homogeneity analysis is developed. For this study, the PL-moments for generalized logistic (GLO), generalized pareto (GPA) and generalized value (GEV) distributions were derived based on the formula defined by Wang (Water Resour Res 32:1767– 1771, 1996). The three distributions are used to develop the regional frequency analysis procedures. As a case of study, the Selangor catchment that consists of 30 sites which located on the west coast of Peninsular Malaysia has chosen as sample. Based on L-moment and PL-moment ratio diagrams as well as Z-test statistics, the GEV and GLO were identified as the best distributions to represent the statistical properties of extreme rainfalls in Selangor. Monte Carlo simulation shows that the method of PL-moments would outperform L-moments method for estimation of large returns period event. Keywords L-moments . Partial L-moments . Regional homogeneity . Frequency analysis
1 Introduction A flood is an unusually high stage of water levels that generally happened in river that overflows and submerges land and inundates the adjoining area. Flooding can caused damages of private and public properties, loss of life and economic problems. In order to ascertain flood control and the forecasting, the estimation of flood magnitude which provides valuable data is a great importance for hydrologic design. However, some of hydrologic processes i.e. floods and rainfalls, are exceedingly the complex natural events. There are resultants number of parameters component and that makes it very difficult to
Z. A. Zakaria (*) Faculty of Informatics, Universiti Sultan Zainal Abidin Malaysia, Terengganu, Malaysia e-mail: [email protected] Z. A. Zakaria : A. Shabri : U. N. Ahmad Department of Mathematics, Faculty of Science, Universiti Teknologi Malaysia, Johor, Malaysia
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model analytically. This estimation of flood is a complex problem which lead to different approaches such as rational method, empirical formula and unit-hydrograph methods that presented by Subramanya (2007). Another approach to the prediction of flood flows and applicable to other hydrologic processes such as rainfall etc. is the statistical method of regional frequency analysis. The estimation of extreme rainfalls quantiles using regional frequency analysis are popular and practical in providing flood information at sites with little or no flow data available to control and forecasting the flood. Hosking and Wallis (1997) developed a new approach to regional frequency analysis based on L-moments estimation met
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