Published in ASCE Journal of Hydrologic Engineering SCALING AND SELF-SIMILARITY IN ONE-DIMENSIONAL UNSTEADY OPEN CHANNEL FLOW Ali Ercan 1 , M. Levent Kavvas 2 , Ismail Haltas 3 1 Assistant Project Scientist, J. Amorocho Hydraulics Laboratory, Dept. of Civil and Environmental Engineering, University of California, Davis, CA, 95616, USA 2 Professor, J. Amorocho Hydraulics Laboratory, Dept. of Civil and Environmental Engineering, University of California, Davis, CA, 95616, USA 3 Assistant Professor, Zirve University, Gaziantep, 27260, Turkey E-mail: aercan@ucdavis.edu Abstract Fractals, dimensional analysis, symmetry, scale-invariance, and self-similarity are interrelated concepts, which help understand the inter-scale relationships in geophysical processes. The processes could be self-similar under certain similarity transformations at certain time and space dimensions. In this study, the conditions under which the Saint Venant equations system for unsteady open channel flow, as an initial-boundary value problem (IBVP), becomes self-similar are investigated by utilizing one-parameter Lie group of point scaling transformations. The advantage of this methodology is that the self-similarity conditions due to the initial and boundary conditions can also be investigated thoroughly in addition to the conditions due to the governing equation of the initial-boundary value problem. The self-similarity conditions for one-dimensional unsteady open channel flow process through irregular channels are derived for time, channel reach length in primary flow direction (x-direction), water depth, channel width, flow area, channel averaged velocity, velocity of lateral flow in x-direction, flow in