Study on Riverbed Evolution After a Severe Sediment Disaster in 2009 at the Confluence Section of Laishe and Neishe Rivers in Pingtung County

Abstract

Typhoon Morakot in August 2009 brought prolonged and intense rainfall to the Lai-She Stream and Nei-She Stream catchments in Pingtung County The accumulated rainfall brought by Typhoon Morakot in three days was as high as 2 241 mm and it caused severe landslides and soil erosions and resulting severe riverbed siltationthreatening the safety of neighboring tribesmen In order to understand the changes of riverbed erosion and siltation in the confluent river reach of the Lai-She Stream and Nei-She Stream after Typhoon Morakot this study collected five measured topography data and related engineering treatment data in the confluent river reach in the past ten years after Typhoon Morakot to study the variation of the riverbed This study also calculated the Laohajin number f and Makawiev number K of the river in the studied reach based on the measured topography data in the period of 2009 to 2018 to evaluate the riverbed stabilityfor further river management The results show that in the view of evaluating river variation in the longitudinal direction the Laohajin number f only considers the sediment size and channel bed slope which is limited in the evaluation of river change while the Makawiev number K with additional consideration of water depth and this make it more better in evaluating river change

Date of Award	2020
Original language	English
Supervisor	Chyan-Deng Jan (Supervisor)