Modeling a 3 sided box culvert

[Slate]

I am trying to model a 3 sided box culvert in which the natural stream bed will retain its shape, but may be lowered to provide a no rise situation for the floodway. I have entered my high and low chord data to define my box (instead of using the culvert editor). This is fine if I do not wish to alter the stream bed in any way, but I want to lower the embankments some to provide additional flow. If I am correct, the stream bed is just interpolated through the box that I have defined using the Bridge Deck/Roadway editor so there is no way I can see to alter the stream bed through my box. How do I do this?

[jarvus lunt]

You are modeling your culvert as a bridge and you want to change the the bottom shape inside of the bridge/culvert?

If so, from the bridge editor, click on Options and select "Internal Bridge Cross Sections"

[Slate]

It looks like that is what I need to do. I tried making a section just upstream and downstream of my box so it would interpolate the stream bed the way I wanted it, but it didnt do it exactly correct. Thanks for your help.

[jarvus lunt]

Another option is you could model your culvert as a series of cross sections with lids.