Use of LL-moments Method for Low-Flow Frequency Analysis
| Autor: | Pin-Ru Huang, 黃品儒 |
|---|---|
| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 In recent decades, the frequency of extreme flood and drought events has increased in many parts of the world, signifying a shift in global climatic pattern. Conventional flood frequency analysis methods are not readily applicable to drought frequency analysis due to large variability in drought duration. The low-end linear moment method (LL-moments), which assign correction factors (m) to extreme value data, had been suggested for the analysis of low flow observations. In this study, the LL-moments is applied to the fitting of empirical time series data from nine stream gages in Taiwan to the general extreme value (GEV) distribution model. Three out of the nine sets of data demonstrated good fit with the general extreme value distribution (GEV) model. LL-moments method was then reapplied to simulated time series generated from known GEV model to investigate the effect of varying the value of correction factors on the reliability of parameter estimation. It was found that for data length less then 29, applying the correction factor of 2 or 3 yielded good parameter estimations, even when an extreme value data of return period of 100 or 200 years was added to the time series. For data length 49, applying the correction factor of 2, 3 or even 4 did not yield good parameter estimation. Further study about applying correction factor greater than 4 would be recommended when data length is greater than 49. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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