A Study of Influential Factors for the Landslide Revegetation in Central Taiwan

Large-scale landslides caused by the catastrophic Chichi earthquake occurred in Central Taiwan. The monitoring of the vegetation recovery could be used for disaster mitigation. Due to scattered distribution of the landslides, satellite images were applied to rapidly monitor and evaluate vegetation recovery for the large-scale landslides. The SPOT images of the Chenyulan Creek watershed, the Ninety-nine Peak area located at Wu River, the Xueshankeng and Wushikeng watersheds at Daan River and the watershed between Tianlun and Techi dam along Dajia River were chosen to identify the spatial distribution of the landslides. Normalized Difference Vegetation Index (NDVI) of the images was used to calculate vegetation recovery rate (VRR) of the landslides. Environmental factors which adapt to envaluate the vegetation recovery efficiency are analyzed by multivariate statistical analysis. Results show that VRR of the landslides at the Chenyulan Creek watershed, the Ninety-nine Peak area, the Daan Creek watershed and the Dajia Creek watershed are 84.6％, 88.7％, 17.1％ and -53.7％ respectively. According to the results of discriminant analysis, at the Chenyulan Creek watershed, 37% of original groups can be correctly classified, and that aspect, geological structure, landuse type and SDR have notable explanation. At the Ninety-nine Peak area, 45.1% of original groups can be correctly classified, and that SDR, aspect, soil type and altitude have notable explanation. At the Daan Creek watershed, 38.2% of original groups can be correctly classified, and that aspect and SDR have notable explanation. At the Dajia Creek watershed, 42.3% of original groups can be correctly classified, and that aspect, SDR and altitude have notable explanation.集集大地震造成臺灣中部多處山區崩塌，震災崩塌地後續之植生復育及防災工作極為重要，而針對植生復育進行監測可做為坡地災害即時評估與水土保持設施規劃設計之用。鑑於崩塌區位分布遼闊且零散，利用遙測衛星影像能快速地監測、評估大範圍崩塌區位之植生復育情形。 本研究以陳有蘭溪集水區、九九峰、大安溪支流之雪山坑溪和烏石坑溪集水區及大甲溪上游自天輪起至德基大壩間之集水區等四個地區為對象，利用地震前後期SPOT衛星影像進行崩塌區位判釋，再以地震五年後之衛星影像進行崩塌區位植生復育率（Vegetation Recovery Rate, VRR）分析，並利用多變量統計分析影響植生復育率之環境因子。 921震災五年後，陳有蘭溪集水區、九九峰地區、大安溪地區及大甲溪地區崩塌區位之植生復育率分別達84.6％、88.7％、17.1％和-53.7％。根據判別分析的結果，在陳有蘭溪地區，坡向、地質、土地利用及泥砂遞移率對於植生復育率有較為顯著之影響，所選用因子對植生復育率分類之準確度可達37％；在九九峰地區，泥砂遞移率、坡向、土壤及高程對於植生復育率之影響較顯著，所選用因子對植生復育率分類之準確度可達45.1％；在大安溪地區，坡向及泥砂遞移率對於植生復育率有顯著之影響，所選用因子對植生復育率分類之準確度可達38.2％；在大甲溪地區，坡向、泥砂遞移率及高程對於植生復育率有較為顯著之影響，所選用因子對植生復育率分類之準確度可達42.3％。摘要 I ABSTRACT II 目錄 III 表目錄 IV 圖目錄 V 壹、前 言 1 貳、前人研究 2 一、遙感探測與SPOT衛星影像之相關應用 2 二、數值地型模型、地理資訊系統及其應用 7 三、常態化差異植生指標 9 四、多變量統計分析之應用 11 五、地震崩塌地與植生復育監測之研究 14 參、研究材料與方法 16 一、研究地區概述 16 二、研究材料及流程 25 三、分析方法 31 肆、結果與討論 41 一、崩塌區位影響植生復育因子 41 二、植生復育率 50 三、多變量統計 61 伍、結論與建議 80 陸、參考文獻 8