Riprap sizing (D50)

HDAT computes a riprap median size proxy \(D_{50}\) from outlet velocity.

Legacy equation

\[ D_{50} = \frac{0.692 \cdot V_{out}^2}{(SG-1)\cdot 2g} \]

Where:

• \(V_{out}\): outlet velocity (\(m/s\))
• \(SG\): specific gravity of rock (dimensionless)
• \(g\): gravitational acceleration (\(\approx 9.81\ m/s^2\))

Engineering notes

• This is a simplified velocity-based sizing proxy; confirm required authority method and safety factors per project spec.
• Record the assumed \(SG\) and any additional protection configuration (aprons, thickness, extents).