Fiber optic piezometers developed by the authors were installed in a single 60 m deep borehole where the profile of pore-water pressure can be monitored at 5m intervals. The test site was located in a section referred to as the Five Turn Point of Highway 18 that connects Chiayi to Alishan, in Taiwan. The highway makes five turns in order to increase the linear dimension and maintain a desirable slope for the vehicles. At least eight sectors within the Five Turn Point area have been identified with either previous slope failure or signs of continuous movement. Subsurface explorations have revealed that the subject area is covered by over 200 m of fractured rock or colluvial material accumulated from earlier landslides. The groundwater could rise more than 20 m as a result of heavy rainfall. The sudden and significant change in groundwater table is believed to be a major cause for the slope instability. The field pore-water pressure profile measurements showed that a heavy rainfall tends to create significant hydraulic gradient in the vertical direction. The distribution of groundwater pressure deviates significantly from hydro-static conditions. It would be difficult if not impossible to capture this phenomenon with the conventional groundwater monitoring technique where one or two piezometers were placed in a borehole. The results demonstrate the advantages of distributive pore-water pressure monitoring by deploying an array of piezometers in a single borehole.