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Submerged weir formula

Submerged weir diagram

Excerpt from: Rajaratnam, N., Muralidhar, D., 1969. Flow below deeply submerged rectangular weirs. Journal of Hydraulic Research 7, 355–374.

In submerged flow, the flow rate depends on the upstream water level \(h_{amont}\) and the downstream water level \(h_{aval}\) (Rajaratnam et al., 1969):

\[Q = Cd \sqrt{2g} Lh_{aval} \sqrt{h_{amont}-h_{aval}}\]

With:

  • L the weir width in m
  • hamont the upstream head on the weir in m
  • haval the downstream head on the weir in m
  • Cd the discharge coefficient (equal to 0.9 by default).

This formula is not recommended for flooding below 80%.

Rajaratnam, N., Muralidhar, D., 1969. Flow below deeply submerged rectangular weirs. Journal of Hydraulic Research 7, 355–374.