Estimation of areal reduction factors using a mixed gamma distribution

SummaryThis study proposes a methodology to estimate the areal reduction factor (ARF) using mixed probability density functions. In practice, ARFs are estimated by using contemporaneous rainfall data from a high density rain gauge network over the basin, which are rarely available. The methodology proposed in this study uses all rainfall data available, whether or not they are concurrent with others. A mixed probability density function is introduced to explain both the rainfall intermittency and variability, and is applied to both point rainfall and areal average rainfall, which are compared to estimate the ARFs. In this study, a mixed gamma distribution was applied for the Geum river basin, Korea, to estimate the ARFs of a one-day (or, 24 h) rainfall as an example. The new method was easier to apply and provided similar results with those of other studies.