# Estimate the flow velocity of a river with satellite images

I'm looking for a more or less straightforward (and not very mathematical) way to roughly estimate the flow velocity of a river based on satellite imagery (e.g. Google Earth).

In more detail: I would like to verify data on flow velocity of rivers that has been submitted to me. Usually it was taken at the side of the river (within 2-5 meters of the river bank. What features would I be looking for on Google Earth to get a rough idea if the submitted values could be correct or are completely off the edge? If there is a sandbank or if the river splits I would assume a slower flow velocity and if I can see wave-like turbulences even on satellite imagery or rivers flow together I would expect the flow velocity to increase.

There is no need to calculate an exact velocity, just to get an idea, let's say in the range of +/- 0.5 m/s if submitted values could be correct.

Are there any other signs I should be looking for on the satellite images that could indicate the flow velocity? Does it make sense at all or does it vary too much across small river sections anyway?

• I don't believe a single velocity measurement taken near the bank has any relationship to the average velocity across the profile. The flow near the bank will be very sensitive to the profile of the river edge - increasing as it goes around points and decreasing between and will be different on the inside and outside of bends. In fact, you often see eddies with flow heading upriver. – haresfur Jun 25 '17 at 21:19
• The velocity profile of any river will be slower velocities at its banks & higher velocity somewhere near the middle. I state "somewhere" because rivers are not uniform open channels with uniform boundary conditions & the flow in them is complicated by rocks, trees, other snags, varying water depths & varying widths – Fred Jun 26 '17 at 3:03
• This is not possible. Rivers are too small. – gerrit Jun 27 '17 at 13:28