宜蘭冬山河流域洪患時空變遷研究

The Spatial-Temporal Changes of Flooding in Dongshan Basin of Yilan County

10.6562/JEE.2012.28.5

林雪美(Hsueh-Mei Lin)；羅煒婷(Lo-Wei Ting)

洪患 ； 時空變遷 ； 冬山河流域 ； flood hazard ； spatiotemporal change ； Dongshan Basin

工程環境會刊

28期（2012 / 01 / 01）

63 - 87

繁體中文

從經濟損失來看，臺灣過去50年以來以水文氣象類災害為主，其中宜蘭地區為臺灣易淹區域之一。根據文獻顯示，其洪患記錄早年即有如：噶瑪蘭廳誌記載嘉慶元年(1796)至道光30年(1850)間，短短50餘年因風災、水患，造成河流改道、田園淹水者達19次之多，圳道損壞情形更是嚴重，其他因位置偏僻或災區較小而未列入記載者不計其數，尤其是得子口溪、宜蘭河及冬山河下游一帶，每當颱風、暴雨來襲，因河水宣洩不及，更是水患頻仍，即便經過多年整治，得子口溪、宜蘭河及冬山河下游一帶仍為現今宜蘭平原最主要的易淹區域。本研究蒐集1961-2010年洪患案例歸納其時空變遷，得知冬山河流域洪患特性變遷呈現複雜性與變動性，長期而言洪患頻度略為增加，發生時間主要為8-10月，空間分布早期為大範圍積淹，自冬山河整治後(1982年)改集中於中下游低窪地區。1991年代起則轉為零星多變，2008年以來中下游地區又開始出現大面積積淹。災因1980年代前多為天然因子所致，後期則以人為及天然因子共同影響。

In terms of the financial lose, hydrology disasters are the major disasters in Taiwan during the past fifty years, and Yilan area is one of the areas that are most vulnerable to flood. According to the literature review, there are more than 19 cases of the changing to the river path or field flood caused by typhoon disaster or flood disaster within only 50 years from 1976 to 1850. The destruction of trenches is most devastating, and other cases, which are not included due to the isolated location or smaller scope, are uncountable. Especially around the area of Dezi River, Yilan River and Dongshan River, the floods were too serious to discharge, and even led to floods whenever the typhoons or rainstorms hit these areas. Even after the renovations for many years, the areas are still the most vulnerable places which are prone to flood in Ilan Plain. Taking Dongshan basin of Ilan County as a case study, this study collected flood cases from 1961 to 2010, and the data were analyzed in terms of spatial-temporal changes and causes. The characteristics of flood of Dongshan basin, including flood frequency, spatial-temporal distribution and cause, are complex and changing. The results in the long term indicate that the frequency of the floods has slightly increased. Most floods mainly happened during August and October each year. Besides, the distribution of flooding used to spread across a large area in Dongshan Basin before 1980. However, after the remediation of the river in 1982, flooding became only to take place in the downstream region. Then, in 1991, the floods began to spread to other different areas irregularly and discontinuously. Nevertheless, according to the previous studies, the results reveal that the distribution of floods has returned to the downstream region again after 2008. Thus, it can be inducted that the causes of floods before 1980 are mostly attributed to natural factors, while those after 1980 are largely mixed with natural and anthropogenic factors.