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Daily Rainfall Disaggregation for Flood Estimation

Author(s): Phuong Cu Thi; James E Ball

Linked Author(s): James Ball

Keywords: Rainfal; Disaggregation; Vietnam; Flood

Abstract: Rainfall is one of the more important factors influencing flows in a river and particularly so for flood flows in a river. Hence there is a need to adequately model rainfall if flows in rivers are to be predicted with reliability. There are three components to a rainfall model, namely the rainfall depth, the spatial distribution of rainfall and the temporal distribution of rainfall. This last aspect of a rainfall model is the focus herein. In many Asian countries, data for assessing the sub-daily temporal distribution of rainfall is limited by the availability of continuous records. It is far more common for daily rainfall records to be available. However, these records are rarely suitable for estimation of flood events. There is a need, therefore to disaggregate these daily rainfall records. One method that has been applied to the problem of disaggregation of daily rainfall records is the“Method of Fragments”. Presented herein is an application of the“Method of Fragments”to the disaggregation of daily rainfall records in the Ba River catchment in Vietnam. In this catchment, 14 daily-read gauges and 12 hourly rainfall stations across the basin were available. The similarity of the these gauges was evaluated using a Welch Two Sample t-test and the Bartlett test for homogeneity of variances to ensure data transfer did not induce different characteristics. Following application of the disaggregation model, the estimated rainfall patterns were validated at 3stations where hourly data was available. Based on the results obtained, application of the“Method of Fragments”to disaggregate daily rainfalls in a monsoonal region is a suitable method for estimating the temporal pattern of rainfall at a resolution suitable for flood estimation.


Year: 2015

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