The Sediment Data editor will populate rows for all HEC-RAS nodes (e.g. cross sections, bridges, culverts, lateral structures, inline structures, etc…) but only requires sediment data for cross sections. Bridges and other non-cross section nodes are grayed out to indicate they do not require sediment data.

Unlike other non-cross section nodes, however, bridges include cross sections that can deposit or erode. Bridges in HEC-RAS replicate the upstream and downstream cross sections on the upper and lower face of the structure and the sediment model will adjust these cross section nodes (link). HEC-RAS will also project the initial sediment conditions associated with the upstream and downstream cross sections with the respective internal cross section.

Modeling Note: Local Scour and Bridge Sediment Limitations

The bridge approaches in HEC-RAS can pose be challenging to apply in a sediment transport model. See the section on bridges and sediment modeling for more on this topic.

Modeling Note: Local Scour and Bridge Sediment Limitations

Federal Highway Guidance for Bridge Scour analysis includes three major components: regional bed level change, contraction scour, and local scour (i.e. pier and abutment effects). The movable bed sediment transport capabilities in HEC-RAS ONLY account for one of those three processes: regional bed change. To compute contraction and local scour use the Bridge Scour tool in the Hydraulic Design editor.