Abstract：A comprehensive investigation of the water-line instability problem of the Three Gorges Reservoir region is of important relevance to hazard migration in a populated region and will benefit greatly local government's plan of rebuilding the Three Gorges Reservoir region and relocating the population. In this paper，it was pointed out that landslide monitoring system，as a foundation of the investigation，must be made in the first stage by developing and establishing a slope deformation monitoring system based on 3S techniques and ground observation networks. The multiple investigative approaches and monitoring networks，including global positioning system (GPS) geodetic networks，lateral earth movement measuring boreholes，pore pressure observing networks and radio remote sensor networks，installed in Wanzhou District，Wushan and Fengjie counties of Chongqing City ever since 1999 were introduced. In allusion to characteristics of natural disasters within this region，various aspects of problems relevant to monitoring system of landslides deformation were discussed. Slopes will be classified firstly by risk index mainly according to geological evaluation and GPS survey results in an area and one can therefore find several critical regions to intensify observation by radio remote sensor networks. The data collected through the multiple investigative approaches are managed with especially designed geography information system (GIS) in which various databases are integrated such as geological prospect data，landslide physiognomy data and hydrological data. Based on this GIS system，observed data can be analyzed，displayed and output in graphics mode. A few representative observation results presented in the paper demonstrate that the proposed monitoring and warning system is an effective approach to investigate slope deformation and can be used to test models of the rock and soil slope mechanics directly through the well-constrained field examples from the Three Gorges Reservoir region.
