This study analyzed the fluvial morphological characteristics of river basins in Taiwan. Torrent characteristics were comprehensively compared and summarized, and the feasibility of torrents division point was assessed.The study area included 26 primary basins in Taiwan. The shape of the basins and the longitudinal profile of the rivers were analyzed. The results showed that when the basin shape is almost circular with an Rc of 0.35 or more, the transverse development space of the drainage is larger. Numerous higher stream orders are available in the downstream. By contrast, the basin shape is long and narrow, the longitudinal profile is relatively simple when Rc is 0.2 or less. When reach elevation is higher than 500 m, the slope of the first order streams in primary basins in Taiwan is higher than 7%,and the watershed area is 200–400 ha. Furthermore, the slope of the second order streams is higher than 4%, and the
watershed area is 1000–2000 ha. On the basis of field investigation, aerial photograph, and satellite imagery, the first and second order streams were verified as possessing torrent characteristics. Therefore, the average reach slope and watershed area of the torrent was primarily defined to be higher than 4% and less than 2000 ha, respectively. In addition to the aforementioned conditions, distinguishing torrents must be verified using field surveys. Moreover, our definition can be applied to determine the torrent division point and to compare it against a range of river division points in the future.
KeyWords: River morphology, longitudinal profile of drainage, torrent characteristic, stream order