I am trying to understand how the sediment concentration of a flow affects erosion. I stumbled across this paper by Bagnold (1968) today that uses a form for the stream power equation that I had not seen before, and haven't yet managed to find anywhere else. Namely:
\Omega = Q g S [\rho + C (\sigma - \rho)]
where \Omega is the streampower, Q volumetric flux of the flow, g is gravity, S slope, \rho is the density of the flow, C is the volumetric sediment concentration of the flow, and \sigma is the density of the sediment.
This implies that the Stream power increases with increasing sediment concentration. I do not understand why this would be the case. I also haven't yet been able to find this relationship anywhere else to give me more context.
My (rather uninformed) intuition was that erosion would decrease as the flow is carrying more sediment - basically because at some point there has to be a limit to how much sediment a flow can carry and it's still a flowing river/stream etc. But if streampower increases with increased sediment then I would expect that erosion would also increase (since that is driven by streampower), which is quite a feedback loop (although obviously deposition would also increase so it's not a simple one).
Can anyone explain what is happening here? Or point me to resources that will help clear up my confusion? I suspect I'm missing something basic, but not sure.