Measuring Velocity Head

Measuring velocity head, H

The board is positioned with the thin edge pointing upstream and the height of flow, h1, measured. Next, the wide side is turned into the flow and the increased height, h2, is measured.

Velocity head, H, is h2 – h1 (ie the increase in height).

Conversion table – converting H into stream velocity

The velocity head measurement can then be converted into a velocity using the conversion table.

Understanding the Physics

The flow of the water has a kinetic energy. When the board is turned wide side on, this kinetic energy is converted to potential energy:

1/2 mv^2 = mgH

v = SQRT 2gH

Level 2 and Level 3 Physics

Tony has used this Physics as the basis of a Physics Investigation for L2 and L3 students. If you are interested in receiving a copy of the L3 assessment, simply email Tony at