I guess what you build has as much to do with what the crossing is used for as it does with the type of structure you build. Mine is the driveway to my house. If I can't get across, I can't leave (or get home). I also have to consider the possibily that a fire truck may have to cross it.
If you can get by with not being able to cross during high water, it would be a lot cheaper to lay down the cement bags. I did this in a creek about 10 years ago and it's still there today.
By the way, the 60" x 20' pipe in the center was $420 and I got it 1/2 price.
