A Quantitative Approach for Classifying Governance Unit of Watershed Management and Flood Mitigation Based on a Long-term Landslide Inventory

Cheng-Chien LIU, Ming-Hsun KO, Huei-Lin Wen, Kuei-Lin FU and Shu-Ting CHANG

Extreme weather makes it difficult to estimate the intensity of typhoon rainfalls, which results in aggravating landslide potential and hazards in forested watersheds. To increase the efficiency of operations and management, it is needed to monitor landslide evolvement continuously, assess quantitatively the classification of landslides, as well as, establish landslide management plans. Take the Qingquan watershed in Wufeng Township, Hsinchu County for example, large-scale landslides occurred in four potential debris flow torrents when Typhoon Aere hit Taiwan in 2004. The Qingquan watershed is classified as 22 optimum watersheds after being processed by hydrologic analysis. The result from overlaying landslide data sheet of these 22 optimum watersheds from 2005 to 2016 shows major landslides occurred mostly during typhoon Aere. After typhoon Aere, vegetation recovery in the landslide zones was getting better, despite landslides occurred sporadically. Only in 2008, landslides occurred near Tuchang bulao caused severe damage. Two large-scale landslide zones, where the average rate of landslide occurrence is higher than 10%, are Debris-flow source areas. Several large-scale landslides occurred by two sides of Shangping Creek flowing through Tuchang bulao, Qingquan bulao, and Minduyou bulao, which are defined as low stability zone and severe landslide. Unstable levels determined by the long-term landslide data sheet of each watershed can serve as a tool to quantify the classification measures of mountain management and flood control of management units. Chinese version of this paper can be referred to [Liu, et al. 2017].

2018/1 427-433