以簡確法評估山棕寮集水區之地滑特性

Landslide Susceptibility Evaluation Based on Simprecise Method-A Case Study in Shang-Zong-Liao Watershed

徐弘明(Hung-Ming Shiu) ； 陳紫娥(Zue-Er Chen) ； 林玉梅(Yuh-Mei Lin)

《中華防災學刊》 6卷1期 (2014/02) Pp. 25-39

摘要

等高線地形圖可以有效表現靜態（坡度）與動態（地形作用）的地形因子，可由其研判坡地穩定性。由於此二地形因子在發生崩山時的改變大，因此很容易由比對前後期等高線地形圖偵測出崩山的位置。相對而言，地滑區的滑動體在滑動過程中，有部分或全部隱藏在地表下，而且因滑動體本體的破壞程度不大，地貌與未滑動前之狀況相去不大，即使利用高科技之衛星影像或高解析度的影像亦難窺其全貌。但是地滑的累積效應可以由比對時距較長的新舊等高線地形圖略窺其貌；本研究以『簡確評估法』為研判準則，利用不同時期等高線地形圖為基本材料，評估山棕寮集水區及其地滑區的發展。結果顯示，二十多年來集水區內地表地形的變動以沖蝕為主，蝕溝不斷加深，也伴隨著潛移與淺層滑動；2000年發生的地滑區，在1977年的地貌特性中即具有弧型地滑之潛在性，1997年該山坡坡面已出現開發行為，地滑區範圍有向上坡擴大的現象。本研究評估此地滑區仍具有滑動之潛在性。

關鍵字

等高線地形圖 ； 弧型地滑 ； 簡確評估法

並列摘要

Slope gradient and some geomorphological processes could be effectively assessed from the contour configuration, hence, topographic maps are great tools for evaluating slope stability. Since slope gradient and surface processes often change drastically after surface slope failures, it is relatively easy to identify slope failures by comparing topographic maps constructed before and after the event. On contrast, the sliding mass of many landslides usually remain relatively intact, and mostly hidden underground, hence, the location and extent of these landslides are difficult to detect even on high resolution satellite images. However, a landslide-prone slope usually gives in gradually and the accumulated topographic changes may be identified from comparing current to very old topographic maps. Based on topographic maps constructed over the past few decades, the ”Simprecise Method” was applied to evaluate slope stability in the Shang-Zong-Liao watershed. It is concluded that surface erosion has been the main geomorphological process in the watershed. As rills deepened over time, slope creep and shallow landslides were initiated. Some geomorphic characteristics pertaining to landslides were identified on the 1977 topographic map at the area where a landslide took place in 2000. Some land utilization was identified on the 1997 satellite image at the same site, and the extent of the unstable area appeared to expand upslope. The study concludes that the slope is still susceptible to landslide hazard.

並列關鍵字

topographic maps ； rotational landslide ； simprecise method