We describe and compare the distributions of three species of riparian tiger beetle in the floodplains of the Tedori River System in Japan. To explain the species distributions, we considered both environmental factors and interspecific interactions, especially the intense competition for food, among the three species. First, we characterized the topography and sand content of the floodplains selected by each species. Cylindera elisae was found on floodplains downstream and those with fine-grained deposits, whereas Cicindela gemmata inhabited only upstream floodplains in mountainous areas with fine-grained deposits trapped by sand-trap dams. Cicindela transbaicalica was distributed widely along the river. Second, we compared mandible size among the species. Interspecific overlap in mandible length was very limited, which suggests that competition for food is weak among these species. These results suggest that environmental factors may be important determinants of the distribution of riparian tiger beetles along the Tedori River.