Inlets located on a grade (S_L > 0) are characterized by an efficiency, E, for a given set of conditions:

Where:

E = Inlet efficiency (unitless)

Q = Total gutter flow (m³/sec, ft³/sec)

Qi = Intercepted flow (m³/sec, ft³/sec)

The flow that is not intercepted is called carryover or bypass flow. It is defined as follows:

Q_b = Q - Q_i

Where:

Q_b = Bypass flow (m³/sec, ft³/sec)