A distinguished universal aspect of wall-bounded turbulent flows is Theodore von Kármán's universal logarithmic law (log-law) of the wall, describing the time-averaged streamwise velocity variation with distance from the wall. The log-law has a universal von Kármán constant κ governing the velocity gradient. There remain a number of cases of the non-universality of κ in fluvial streams. In particular, it behaves as a variable in flows with low submergence, or if there is bed- and suspended-load transport. This research focuses on the non-universality of κ raising various issues and inviting future research directions. © 2010 International Association for Hydro-Environment Engineering and Research.