Harshit,

In an open channel flow, pressure distribution in the vertical follows the hydrostatic law which says that pressure increases linearly from atmospheric pressure at the water surface to a maximum value at the bottom. 

Water pressure (p) at any depth H from the surface will be given by,

p = gamma * H

where gamma is the unit weight of water (9810 N/m3).

You can thereby calculate the pressure at the bed if you measure the total depth of water in the channel at the desired location. Depth of water in an open channel can be easily measured using a point gauge.

Good Luck!

Thank you sir for your kind answer.

However, I am not measuring pressure in the Hydrostatic region. My studies are on RVF where the assumption of Hydrostatic Pressure isn't valid. I was looking for an instrument that give the pressure readings on the channel bed without disturbing the flow. This would then help me to further the understanding of RVFs.

I look forward to your kind suggestions.

Thanks