陳有蘭溪集水區災後山坡地土地可利用限度查定快速評估之研究

GIS-based Rapid Assessment for Classification of Utilizable Slopeland Limitation Following a Disaster Event in the Chen-You-Lan Watershed

張庭瑜(Ting-Yu Chang) ； 王湘閔(Siang-Min Wang) ； 林昭遠(Chao-Yuan Lin)

《中華水土保持學報》 46卷3期 (2015/09) Pp. 158-170

https://doi.org/10.29417/JCSWC.201509_46(3).0004

摘要

臺灣水土保持工作最早乃由農林邊際土地調查開始，針對有關土地可利用限度進行查定，隨著山坡地開發面積逐漸增加，在極端降雨事件下，崩塌所影響之面積亦逐年上升，依據「山坡地土地可利用限度分類標準」，地籍之土地特性為崩塌或地滑時需判定為加強保育地，待邊坡穩定植生恢復後，方可重新耕作，然水土保持局之查定工作人員有限，面對大面積之崩塌事件，無法一一至現地進行查定工作，因此山坡地土地可利用限度如何於災後進行快速查定檢討乃水土保持局重要之議題。本研究以南投縣信義鄉之陳有蘭溪集水區為樣區，應用遙測技術配合地理資訊系統分析平均坡度、土壤有效深度、土壤沖蝕程度及母岩性質等四項查定因子，據此成果建置災後山坡地土地可利用限度分類快速檢討。研究中利用數值高程模型分析平均坡度；以地形濕度指數推估土壤有效深度；土壤沖蝕程度則採用通用土壤流失公式進行評估；母岩性質則採預設值，套疊上述因子所得分類結果與水保局原始查定結果為78%之符合率，但經現場取樣調查判釋，本研究方法之分類結果無誤。此外藉由SPOT-5衛星影像萃取莫拉克颱風（編號：200908）之崩塌區位，可作為山坡地土地可利用限度查定即時更新之依據。

關鍵字

山坡地土地可利用限度查定 ； 地形濕度指數 ； 地理資訊系統

並列摘要

At an early stage, the Soil and Water Conservation Bureau (SWCB) conducted a field survey to delimit marginal agroforestry land. In 1976, the ＂Slopeland Conservation and Utilization Act＂ was promulgated as well as the classification of slopeland utilization limitations becoming standardized. In the last decade, due to extreme rainfall events, numerous landslides frequently occurred in mountainous areas. According to the act, the land damaged by the disaster must be categorized as conservation land where rehabilitation is required. Nevertheless, large-scale disasters on slope land are under the constraint of field investigation by SWCB officers. A rapid post-disaster procedure for slopeland suitability evaluation should be initiated. Chen-You-Lan Watershed was selected as a case study. The slopeland classification criteria parameters, i.e., average slope, effective soil depth and degree of soil erosion for a given cadaster unit were derived and/or calculated from the Digital Elevation Model (DEM), Topographic Wetness Index (TWI) and Universal Soil Loss Equation (USLE), respectively, using Geographic Information Systems (GIS). The parent rock criterion was assumed to be soft rock. The result showed the concordance of slopeland suitability classification between the SWCB field survey and GIS-based rapid assessment give an overall consistency of 78%. However, the classification method in this study is correct according to the field survey. In addition, the post-disaster areas of Typhoon Morakot in 2009 were interpreted using SPOT-5 satellite imageries. It was found satellite based real time disaster mapping technology can be used to specify the intensive conservation areas.

並列關鍵字

Assessment for classification on slopeland utilizable limitation ； topographic wetness Index ； geographic information system