Recent changes in the suspended sediment discharge in the Chenyulan watershed, Taiwan

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J.C. Chen, Sen-Shun Huang, Ji-Shang Wang, Tsung-Feng Huang

Wednesday 1 july 2015

12:36 - 12:39h at North America (level 0)

Themes: (T) Extreme events, natural variability and climate change, (ST) Hydrological extremes: floods and droughts, Poster pitches

Parallel session: Poster pitches: 9I. Extreme - Flood Drought

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This paper examines the variation in the characteristics of rainfall events triggering numerous debris flows and the effects on the suspended sediment discharge in the Chenyulan watershed, central Taiwan. The data of rainfall, runoff, or water discharge Qw and suspended sediment discharge Qs were collected from three meteorological stations and the Neimaopu hydrological station located in the watershed during the past few decades (1980–2012). Five extreme rainfall events with the rainfall index RI > 365 cm2/h and the severe Chi-Chi earthquake (CCE) are selected. The relationships between Qs and Qw at various periods, such as between extreme rainfalls or between extreme rainfall and the CCE, are analyzed. The changes in Qs or the ratio of suspended sediment discharge ( r) at various Qw are presented and discussed. The relationship between r and RI is also presented. The results show that Qs at Qw = 10~100 cms after suffering extreme rainfall events, and the CCE is 2~7 times greater than that without suffering extreme rainfalls or severe earthquakes in the watershed. The Qs increase could be related to abundant loose sediment caused by the CCE and extreme rainfall events caused numerous debris flows during the 2000s.