HELP with a HEC-RAS Multiple Opennigs Hydraulic Model

I have this river I am modeling, Denton Creek that divides into a main channel and a slough 200 feet upstream and comes together 1200 feet downstream. There is an existing bridge on the main channel and a Relief bridge south of it over the Slough on the same road, FM 156. Each structure is parallel to a railway bridge about 120 feet west of FM 156. I am trying to modthe roadway bidges as a "Multiple Openning" problem. I have the following questions:

1) To establish the stagnation points, do I use the "Multiple Opening Analysis" tool on just the roadway bridges?

2) Each time I use the "Multiple Opening Analysis" tool on the roadway bridges and the RAILROAD bridges downstream I get an error message.

3) Should I be modeling this problem with a Multiple Opening Approach?

Some one please help?

Dear Francis :

If the flow divides into two separate reaches, then you should model them as two separate conveyance areas. The multiple opening option is for bridges openings that are closely connected, where the conveyance can balance through them quite easily.

Note that we have a split flow example on our website that demonstrates how to do this.

If you have any additional questions or need any further information, please contact me again.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com