Combined with the spatial data processing capabilities of GIS

a calculation method for reservoir bank landslide speed based on grid column elements was proposed. The Pan Jiazheng method was extended from two-dimensional to three-dimensional. A three-dimensional (3D) landslide speed calculation model based on grid column elements was first established

and the spatial computational expression of each parameter in GIS was clearly specified. Secondly

based on the Newton's law of motion

the dynamic equilibrium equations were established along and perpendicular to the sliding direction to derive the three-dimensional landslide speed. Finally

an expanded module of 3D landslide speed calculation was embedded in GIS platform

and the result of a case study was compared with that obtained from the Pan Jiazheng method. The results showed that compared to results from the Pan Jiazheng method

the maximum speed calculated by the method in this paper is 15.2 % higher and the acceleration is 32.8 % higher

and 1 s shorter for reaching the maximum speed.