The aim of this study was to quantify the environmental impacts of dams, used for the control of riverine water resources, through life-cycle assessment techniques. The studied pneumatic and upright rubber dams had sizes of 500 mm (H) × 15,000 mm (L) and 2,000 mm (H) × 15,000 mm (L), respectively. The characterization values of the dams were compared in view of global warming. If the pneumatic and upright rubber dams both had sizes of 500 mm (H) × 15,000 mm (L), they would emit 5.365E + 05 kg CO 2 -eq and 5.441E + 055 kg CO 2 -eq, respectively. Meanwhile, if they both had sizes of 2,000 mm (H) × 15,000 mm (L), they would emit 2.193E + 06 kg CO 2 -eq and 2.094E + 06 kg CO 2 -eq, respectively.These results indicated that the environmental impact of dams can be strongly influenced by their size and construction method. In particular, their operating energy and the characteristics of their raw and subsidiary materials were the highest-ranked environmental impact factors in our sensitivity analysis. Therefore, in order to reduce greenhouse gas emissions, the environmental impact of river structures with a relatively long lifetime should be pre-evaluated when their construction is being planned.