921集集大地震與莫拉克颱風崩塌地在崩塌發生前之坡形分類

Distinguishing the Slope Shapes of Pre-landslide Terrain inLandslide Areas Caused by 921 Chi-Chi Earthquake and Typhoon Morakot

蔡義誌(Yi-Zhih Tsai) ； 馮智偉(Jhy-Wei Ferng) ； 陳樹群(Su-Chin Chen)

《農林學報》 60卷4期 (2011/12) Pp. 275-292

https://doi.org/10.30089/JAF.201112.0002

摘要

本研究以九大坡形的概念進行崩塌地在崩塌發生前的地形分類，並且統計九個分類所占比例，以討論坡形與崩塌潛勢之關係，說明坡形可能影響崩塌敏感性，而且可視為崩塌特性之一。在研究中，嘗試建立九大坡形的基本單元坡形及其數值高程模型，用以與崩塌前的真實地形進行比對，區分出坡形分類。這樣的坡形比對技術，能呈現出一個完整的、整塊崩塌地的代表坡形，非單一網格的坡形，也非數個網格的坡形集合。將此技術應用於921集集大地震與莫拉克颱風發生前的數值高程模型上，獲得崩塌發生前的地形坡形分類。其結果為，921集集大地震以內聚凸坡形成的崩塌占最多（25.25%），大多存在於山脊陵線、坡頂及陡崖邊緣等處；莫拉克颱風則以內聚直坡占最多（30.25%），這類坡形通常位於低窪處，容易匯集雨水而使水分集中，產生較大的孔隙水壓而引起崩塌。此外，再以變異數分析與Post Hoc檢定探討九種坡形分類對崩塌地面積、坡度、坡向、高程之影響程度，並在5%的顯著水準下進行同質性區分，結果表示崩塌前的坡形分類會與崩塌面積、坡度、坡向或高程之分佈息息相關，因而在討論崩塌特性上坡形分類是有其必要性。

關鍵字

崩塌 ； 九大坡形 ； 坡形分類技術

並列摘要

The concept of nine slope shapes was used on comparing digital elevation model (DEM) with slope shapes, and distinguishing pre-landslide terrain in landslide areas which were triggered by Chi-Chi earthquake and Typhoon Morakot in this study. Statistics for nine types of slope shape classification were discussed for the relationships between slope shapes and landslide potential. Slope shape can probably affect the susceptibility of a slope to landslide, and can be regarded as one of landslide characteristics. In this research, the digital elevation models of nine-unit slope shape were established to match with pre-landslide terrain and distinguish slope shape classification. This slope shape matching technique showed the representative slope shape of a complete landslide area, not that single grid cell. The technique was applied to compare DEM and distinguish pre-landslide terrain of Chi-Chi earthquake and Typhoon Morakot. The results were that convex-concave slope shape in Chi-Chi earthquake has the largest proportion (25.25%), and was found on the ridge, the top of hill or the edge of cliff. Linear-concave slope shape in Typhoon Morakot has the largest proportion (30.25%), usually located in the lower section of a profile where existing the convergence of percolated water. Furthermore, statistical tests were discussed with nine slope shapes and landslide area, slope, aspect, elevation by analysis of variance and post-hoc analysis with 5% significance level. These indicated that nine slope shapes of pre-landslide are statistically significant and correlation of spatial distribution to landslide area, slope, aspect, elevation. Therefore, it is necessary to distinguish the slope shapes for discussing the characteristics of landslide.

並列關鍵字

Landslide ； Nine slope shapes ； Slope shape distinguishing technique