Extreme weather events induced by climate change are increasing across the world. In particular, floods resulting from unpredictable heavy rains cause significant damage to property and human life. In Korea, river and underwater structure management is performed continuously in accordance with strict regulations. However, to prepare for unprecedented downpours, the structures of river reservoirs must be reinforced and their stability must be evaluated. This study focuses on the stability evaluation of piping, which represents the main cause of weir collapse. To this end, sheet piles are applied to weirs to evaluate the effects of changes in their length and location on their seepage discharge, seepage velocity, and maximum hydraulic gradient. Additionally, piping stability evaluation of weirs is conducted using sheet piles by evaluating the critical velocity. The results derived in this study are expected to be highly beneficial for reinforcing weirs currently in operation as well as for the design, construction, and operation of future underwater structures.