台灣東部地區懸浮沉積物與山崩在颱風事件中的相對應關係

Abstract

本研究利用同步輻射光源進行X光繞射，嘗試來了解卑南溪及花蓮溪流域之懸浮沉積物所含礦物組成之變化。另外以福衛星2號影像資料，來判釋本研究區域在2008年至2009年間崩塌地的分布狀況，並與集水區內的流量、降雨量等資料，來探討懸浮沉積物中所含礦物種類、含量與山崩間的相對應關係。 調查結果顯示，卑南溪各子集水區在薔蜜颱風後之崩塌率介於1.17 %至1.79 %之間，莫拉克颱風後崩塌率介於1.42 %至4.5 %之間，其中以鹿野溪流域之崩塌率最高。花蓮溪各子集水區在薔蜜颱風後崩塌率介於1.29 %至2.90 %之間，莫拉克颱風後崩塌率介於1.53 %至3.72 %之間，其中以壽豐溪流域崩塌率最高。另外，從卑南溪及花蓮溪的採樣發現，本研究區內之礦物主要包含鈉長石、黑雲母、方解石、綠泥石，以及石英。當流量小於40 m3/s時，其細顆粒(<0.01mm)之含量與流速呈現正相關。當流量大於40 m3/s時，其細顆粒之含量會降低至10 %左右，當流量大於500 m3/s時，細顆粒含量與流速又呈現正相關。颱風過後，研究區內之崩塌率越高，其礦物的重量變化也越大。

This study used the Synchrotron Radiation analyzing the minerals composition in suspended sediment along the catchments of Beinan and Hualian River. The landslide areas were measured by using the Formosa II images from 2008 to 2009. We try to find the relationship between the rainfall, sediments discharge, minerals contents with landslide. Investigation results indicated that the landslide ratio ranged from 1.17% to 1.79% in Beinan watersheds in the post Jangmi Typhoon 2008 and the ranged from 1.42% to 4.5% in the post Morakot Typhoon. The landslide ratio ranged from 1.29% to 2.90% in Hualian watersheds in the post Jangmi Typhoon 2008 and the ranged from 1.53% to 3.72% in the post Morakot Typhoon. The mineral composition analysis reveals that the major minerals of study area include Albite, Biotite, Calcite, Chlorite-serpentine and Quartz. The contents of fine fraction have a positive relation when the flow discharge less than 40m3/s. The contents of fine fraction will descend to 10% when the flow discharge over 40m3/s. When fine fraction have a positive relation when the flow discharge over than 500m3/s. Post Typhoon, the weight of minerals have a positive relation when the landslide ratio higher.