2001年桃芝颱風造成臺灣大學實驗林管理處溪頭營林區內的大學坑集水區發生土石流，災後復建工程進行的調查，鑽探結果研判其崩積層應在50m以上。降雨快速入滲，使大學坑有豐沛之自由地下水量。水位資料顯示大學坑堆積區暴雨期間的水位最高可達-1m，枯水期則降低至-30m，落差極大，且地下水流動特性並非均質，受土石流動堆積層次影響甚深。輔以食鹽水檢層試驗結果顯示，淺層崩積層內粗大孔隙所形成的伏流水為大學坑最主要的自由地下水流動形式，流動層次應在地下0m~15m之間。再者，本研究改良舊有食鹽水檢層方法，利用Schlumberger所產之CTD自計式水位計配合電動捲線器進行試驗，此方法可節省現場試驗人力，也可簡化室內分析步驟，值得未來加以推廣使用。

In 2001, the typhoon Toraji caused a massive mudslide at the university gully watershed of the Xitou tract, the Experimental Forest of National Taiwan University. According to the borehole investigations of reconstruction, the colluvial deposit depth is more than 50m in deposition region. Rapid land surface infiltrations caused by heavy rainfall in Xitou area resulted significant amounts of subsurface flows. The water level results showed the highest water level was near -1m during heavy rainstorm period, and the lowest water level was near -30m during dry season. The results also indicated the flow character of groundwater was not homogeneous, which was influenced by the deposit pattern of colluvial. Integrated analysis from precipitation, water level and salt logging results indicated that the major groundwater style was subsurface flow in vadose zone with the flow depth being between 0m to 15m. Furthermore, this study improved the instructions of salt logging test by using a Schlumberger (conductivity-temperature-depth, CTD) diver logger and an electric fishing reel. Our new salt logging test procedure can save the man power during outdoor testing and also can simplify the indoor analytic procedures. This new protocol can be promoted in the future.