衛星影像判釋與現地探查天然林集水區新生崩塌地分布之比較： 以 2015 年蘇迪勒颱風誘發崩塌為例

Typhoon Soudelor brought high-intensity, short-duration rainfall and was the largest typhoon event to strike Taiwan in 2015. However, the effects of the typhoon on natural forested areas have been little reported. This study investigated the spatial distribution of new landslides in the Tsukeng catchment in Fushan Experimental Forest and compared their effects through satellite images and field investigations. Based on satellite image analysis, 62 new landslides were induced by the typhoon. The surface area of the landslides increased with slope gradient, except for areas of stream-bed fluctuation. The characteristics and types of landslides were different along three field investigation lines. The Shuiguan trail showed smaller landslides but included four types, namely cracks, collapses, gully expansions, and compounding. For 56% of the landslides occurring at downslope locations along the Tsukeng stream, cracks or collapses were also found at corresponding locations in the upslope direction along the Shuiguan trail. It suggests the consecutiveness of mass movements between the upslope and downslope, as well as impending movements at these locations in the near future. Since these effects are barely detectable from satellite images alone, it is necessary to use them in combination with field investigations to collect the greatest amount of information possible.蘇迪勒颱風帶來的短延時強降雨為2015年影響臺灣最大的颱風事件，然而蘇迪勒颱風對人為干擾少 之天然林區域所造成的影響還少有研究調查，本研究調查蘇迪勒颱風後對於福山試驗林粗坑溪集水區內的新 生崩塌地的分布，並比較衛星影像圈繪以及現地探查所得結果之異同。根據衛星影像分析，新生崩塌地總計 62處，除了河道變動外，崩塌面積隨著坡度上升而擴大。三條現地探查路線之崩塌型態不一致，其中水管步 道之崩塌規模雖然小，但卻包含裂縫、山壁崩塌、沖蝕溝擴大、兩者以上的複合型態。粗坑溪沿岸處崩塌事件 中有56%可以在上坡之水管步道中找到位置相對應的裂縫或崩塌，可能為上下坡面塊體連續移動，這些區域未 來再次擴大、移動、滑動的可能性高；然而若單以衛星影像難以得知此徵兆，凸顯結合現地探查之必要性及 優點