One component of Total Additional Structure Losses () is the energy loss due to plunging inflows.

See also: HEC-22 (Third Edition) Additional Structure Losses.

All piped and locally injected inflows to the structure are evaluated to see if plunging conditions exist. If so, and proportionally, those inflows contribute to the computed additional loss due to plunging (). A piped inflow is classified as plunging if the elevation of inflow () exceeds the energy level in the structure (). (See also: HEC-22 (Third Edition) Entrance Loss.

Note: Locally injected or intercepted flows at the node are also included as a contributing plunging inflow if the top or rim elevation of the structure () exceeds this energy datum ().

The additional energy loss contributing to plunging inflows to the structure is the weighted sum of all plunging inflows to the structure. Generally, a composite plunging inflow coefficient () is calculated, and then applied against the known Entrance Loss ().

= Plunging Inflow Coefficient

= Relative Entrance Loss (See also: HEC-22 (Third Edition) Entrance Loss.

The coefficient () is used in the procedural steps for computing the junction loss at the structure. Detailed plunging results are also calculated for each individual inflow pipe into the structure of interest, for reporting reasons.

= Contributing Plunging Inflow

= Plunging Height

= Plunging Elevation

= Outflow Pipe Diameter (or Equivalent Diameter)