Corridors for Streams (with Sample Drawing)

More follow up from my Autodesk University class on Ditches and Streams…Â

Some folks came up to me after the class and said that they really enjoyed the class and loved the stream- but they would never be able to repeat what I did back at the office.

So my mission over the next few weeks- help you repeat it!

I’ve included some explaination and screen captures, as well as a drawing with a completed stream for your download. Dig into the drawing and tear it apart to learn how you might construct your corridor.

Click MORE to learn how and get the drawing….

Remember that corridors are a SCULPTING TOOL.  Just as you can mix and match playdough colors, use different tools to cut playdough and different squeezes to shape playdough… you can use different attachment points, transitions and targets to bend and stretch a corridor into almost anything.

Keep in mind that I showed a stream with a changing cross section- but flip it over, and it’s a berm.  Widen it up, and it’s a pond.  Use your imagination.  Corridors can be used for MUCH MUCH more than roads.

There is no right or wrong way to build a house, right?  You just combine materials and tools together in a sound way that makes sense for your design constraints.  If you learn how corridors are put together, you can combine alignments, profiles and assemblies in any sound way to meet your design constraints.

(Here is a teaser—- Pond as Corridor coming to a post soon!)

Ok, so back to the river.

With that in mind, you need to familiarize yourself with Alignments, Profiles, Assemblies and Corridors before you will be successful.  Do the tutorials, seek online resources and learn them as “roads” first, even if you never do road design.  Then, download the drawing from this post and try it with your own data.

I also must insist that you become familiar with site geometry and realize that parcels WILL FORM when you make your target alignments. (and that is OK)  To read up on site geometry visit:


Corridor Ingredients:

Baseline Alignment and Profiles (on their own Profile View)


Target Alignments and Profiles (don’t have to be on their own Profile View)

Here is what our profile looks like:

And here are our sections:

Since the STEP and POOL sections are only good for ONE INSTANT (at the PVI locations for each type respectively), we will trace the paths that the Top and Bottom of Bank will make.  This slides the assembly larger and smaller as it moves down.

Trace with polylines….

Smooth/Fit as appropriate….

Define as alignments (pay attention to site geometry here)

Make Assemblies for both sides of the river….

Build your corridor…. (note empty space in middle)

Build your corridor surface (TIN fills in empty space)

A Stream! (or berm or pond or anything!)


Click below to download sample drawing:Â

Stream Corridor Sample Drawing



  1. rferguson says:

    WOW! This is pretty awesome. Thanks for posting some of your info from AU. Unfortunately, I was unable to go this year. Hopefully, I can go next year and get a chance to met all of you guys who have helped me out big-time all year long!


  2. Indeed Cool Dana.
    Believe it or not, Rebecca, they are better live than on line.
    The AU stuff ought to be ready for download in a week or two, I’m guessing. Some good stuff this year.

    Uncle FUD

  3. Chris P says:


    I really enjoyed your class on upside-down roads as streams. That’s exactly what we do at my firm.

    Back in the office after my swollen head recovered, so much knowledge gained this year at AU; I got some strange looks describing the concept of arroyos being modeled as inverted roads. Ha

    Once I show them for real, their eyes will uncross. Thank you for sharing the example data.

    Have a most wonderful holiday