Estimating peak flow-discharge during extreme rainfall events for the Gao-ping river, Taiwan

Abstract

Typhoon Morakot struck central and southern Taiwan on August 8, 2009. The high intensity and accumulation of rainfall induced floods, landslides and debris flows. During Typhoon Morakot, the flood level was beyond the design limit of many river embankments in southern Taiwan. It is, therefore, desirable to estimate the peak flow-discharge for similar extreme rainfall events in future. In this study, the destructive flood in the Gao-ping river in southern Taiwan, caused by Typhoon Morakot, was selected as an area for case analysis. First, hydrological and geomorphological data for historical typhoons together with rainfall data were collected and analyzed. Next, the rational method, combined with a number of equations, was proposed to estimate peak flow-discharges in the river produced by extreme rainfall events. The estimated peak flow-discharges of historical events were then compared with the observation data acquired from stream gauge stations and previous studies. The results showed that the proposed method is able to estimate the flow-discharge in the Gao-ping river with reasonable accuracy if the flow rate of interest is greater than 5000 cms or the return period of interest is more than 100 years. It could, therefore, be used to determine the peak flow-discharge for extreme rainfall events.