Study on the Influence of the Rainfall Variability on the Number and the Probability of Debris Flow Occurrence in Chenyulan Watershed

• Main Authors: Yang Yu Shiuan, 楊育瑄
• Other Authors: Chen Jinn Chyi
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/50126223318938741783

碩士 === 華梵大學 === 環境與防災設計學系碩士班 === 98 === The variability in rainfall related to the number of debris-flow occurrence and probability of debris-flow occurrence in the Chenyulan stream watershed located in Central Taiwan in last few decades was studied in this work. The rainfall data taken from three meteorological stations and the events of debris flow occurred in the watershed within the period of 1948 or 1960 to 2009 was collected. The yearly variations of the representative rainfall characteristics, including the daily maximum rainfall intensity and the daily rainfall, in the watershed based on the data measured at meteorological stations were analyzed. Analyzed results showed that higher daily maximum rainfall intensity or daily rainfall events had higher increasing trends since 1948 or 1960. The number of debris-flow occurrence also increased with increasing in the daily maximum rainfall intensity or the daily rainfall depth of debris-flow occurrence. When the daily maximum rainfall intensity of debris-flow occurrence exceeded 45 mm/hr, the number of debris-flow occurrence was approximately increased by 5% each year in the Chenyulan stream watershed. The probability of debris-flow occurrence  was approximately increased by 0.13% each year when the daily maximum rainfall intensity   exceeded 30 mm/hr, and the value of   was approximately increased by 0.12% each year when the daily rainfall depth   exceeded 400 mm. In future 10 years, 2010-2020, the probability of debris-flow occurrence evaluated by Logistic regression analysis in the watershed was estimated by increasing 12% when  =35 mm/hr and increasing 8% when =200mm.