In general, the default methodology for encroachments at bridges, culverts, and multiple openings, is to use the downstream computed encroachments through the structure, and at the cross section just upstream of the structure (the program does this automatically). There are a few exceptions to this rule.
First, when using Method 1, the user can enter separate encroachment stations downstream of the structure and upstream of the structure. The encroachments inside the structure will be based on what is entered outside (i.e. the encroachment inside the structure on the downstream side is based on the encroachment outside the structure on the downstream side. The upstream inside encroachment is based on what the user places for the cross section upstream and outside of the bridge).
Second, for encroachment methods 2 through 5, the program will allow for separate encroachment calculations at a bridge, when using the energy based bridge computation method. For all other bridge computation methods (Momentum, Yarnell, WSPRO, Pressure Flow, Pressure and Weir Flow, and Low Flow and Weir Flow) the program will use the computed downstream encroachments through the bridge and at the cross section just upstream (as long as the cross section stationing is consistent from downstream to upstream of the bridge).
At a culvert crossing or a multiple opening, when using encroachment methods 2 through 5, the program will always use the computed downstream encroachments through the structure and just upstream of the structure. The only way to override this is to use Method 1 encroachments.
Also, encroachments can be turned off at any bridge, culvert, or multiple opening.