<p>An essential characteristic of sedimentary particles is their shape, which allows for formulating geographical hypotheses about abrasion, transport distance, river behaviour, etc. This research article focuses on exploring the longitudinal variation of channel bedload characteristics. It focuses on the process-response relationship between channel flow and particle shape of the River. To fulfil the objectives Wolman’s pebble count method, Cailleux roundness, Power’s roundness-sphericity, pebbles morphometric attributes (e.g. Flatness ratio (FR), Elongation ratio (ER), Co-efficient of flatness (CF), Maximum projection sphericity index (MPSI), Oblate-prolate index (OPI), Roundness index), and bivariate plots were executed. In this research, 100 samples were collected from each experiment site of the Balason River. The present work efforts are to study sediment particle roundness at the river network scale, and to prosecute sediment sampling efficiency in the field. By amplifying the results a mean value as representative was calculated 0.65, 0.27, 0.46, 0.71, and 42.94 for MPSI, OPI, FR, ER and CF respectively. The bivariate plot of sphericity index vs. flatness index and OPI vs. sphericity index shows that all the sites (i.e., Upper Dudhia, M. M. Terai, New Rangia and Matigara) were more diagnostic of the fluvial depositional environment. In the Balason River Basin (BRB), there are two dominant geological formations, i.e. Darjeeling Gneiss and Alluvium (recent and sub-recent). Therefore, in the study region, channel bed materials are modified through fluvial processes. This investigation thus showed that river depositional processes were responsible for the channel bed loads (Gravel-Unlithified) in the study area. To view the implications of the study the researchers tried to explain the interconnectedness among rock characters within the geological formations along with the supply of loads and the character of the fluvial dynamic to understand the modified riverine environment.</p>