氣候變遷衝擊下脆弱環境之永續發展策略建立－以台東地區為例-氣候變遷下水文環境敏感區的動態變化及原住民社區的因應策略之研究－以台東太麻里溪流域為例(I)

Abstract

頻率分析常被應用於防災規劃、水工設計及災害風險評估中，透過適當的機率分佈可推估最大降雨量或洪峰流量，有助於人們瞭解集水區內的水文特性，提升集水區經營管理之效率。本研究以台東的太麻里溪集水區作為案例，從1982年至2009年間，針對極端水文事件包括年最大日流量以及年一日最大雨量進行頻率分析，比較極端值第一型分佈、對數常態分佈、皮爾森第三型分佈及對數皮爾森第三型分佈之適切性，並據此探討近期氣候變遷之趨勢。結果顯示，研究區內年最大日流量頻率分析以極端值第一型分佈最為適切，後期(1996-2009年)的最大日流量推估值均比前期(1982-1995年)高出許多，變動率介於37.93%至57.88%間，後期的年最大日流量平均值也比前期高出40.63%，標準差更高出67.94%。另外，年一日最大雨量頻率分析則是以極端值第一型分佈及對數常態分佈為佳，後期的年一日最大雨量推估值均比前期高，變動率介於10.27%至59.25%間，後期的年一日最大雨量平均值比前期高出16.09%，標準差則高出109.30%。整體而言，太麻里溪集水區的年最大日流量及年一日最大雨量均逐漸增高，變動率大，頻度亦增強，顯示出未來的極端水文事件將具有上升之趨勢。

The frequency analysis is often applied in disaster prevention planning, hydraulic works design, and hazard risk analysis. It is possible to estimate the maximum volumes of intensive rainfall and peak discharge based on a suitable probability distribution. The frequency analysis is also helpful for people to understand the hydrological characteristics in a watershed, and to enhance the efficiency of watershed management. The Taimali stream watershed is selected as a study area in this research. The extreme hydrological events are analyzed including the annual maximum daily discharge and annual one-day maximum rainfall during the period from 1982 to 2009. There are four probability distributions are compared including extreme-value type I distribution, logarithmic normal distribution, Pearson type III distribution, and logarithmic Pearson type III distribution. Moreover, the current trend of climate change is also discussed based on the frequency analysis. Results show that the extreme-value type I distribution is more suitable for the frequency analysis of annual maximum daily discharge. The estimated annual maximum daily discharges in late stage (1996-2009) are higher than that in early stage (1982-1995). Their variation is from 37.93% to 57.88%. The average of annual maximum daily discharges in late stage is bigger surpassing up to 40.63%, and the standard deviation is also exceeding up to 67.94%. In addition, the extreme-value type I distribution and logarithmic normal distribution are more suitable for the frequency analysis of annual one-day maximum rainfall. The estimated one-day maximum rainfalls in late stage are higher than that in early stage. Their variation is from 10.27% to 59.25%. The average of annual one-day maximum rainfall in late stage is bigger surpassing up to 16.09%, and the standard deviation is also exceeding up to 109.30%. In conclusion, there is an increasing trend for the annual maximum daily discharge and annual one-day maximum rainfall in the Taimali stream watershed. The variation is enhancing and the frequency is strengthening. It reveals that the occurrence probability of extreme hydrological events is rising in the further future.