The studies of waterfalls and knickpoints have mostly focused on the erosion processes and recession rate but have seldom discussed the influences of sediment deposition upon the morphology of waterfalls. This study investigated the geomorphic changes and channel bed variation of the Meng-Gu Waterfall, Nanshan Stream, by comparing historical photographs and terrain surveying by UAV. The channel bed has experienced two cycles of deposition and erosion since 2004. Typhoon Mindulle in 2004 and Sinlaku in 2008 both caused large channel bed rises of 13 m. The lower step of the Meng-Gu Waterfall had been buried by thick sediment deposition and will not appear again because the rise of the base level of erosion after the check dam construction downstream in 2009.