The culvert routines in HEC-RAS and HEC-2 were adapted from the Federal Highway Administrations Hydraulic Design of Highway Culverts publication, HDS No. 5 (FHWA, 1985). The following is a list of the differences between the two programs.

  1. HEC-2 can only perform culvert calculations for box and circular culvert shapes. HEC-RAS can handle the following shapes: box; circular pipe; semi-circle; arch; pipe arch, vertical ellipse; horizontal ellipse; low profile arch; high profile arch; and ConSpan.
  2. HEC-RAS also has the ability to mix the culvert shapes, sizes, and all other parameters at any single culvert crossing. In HEC-2 the user is limited to the same shape and size barrels.
  3. HEC-RAS has the ability to use two roughness coefficients inside the culvert barrel (one for the top and sides, and one for the bottom). This allows for better modeling of culverts that have a natural bottom, or culverts that were designed for fish passage.
  4. HEC-RAS allows the user to fill in a portion of a culvert. This allows users to model culverts that are buried.