Tuesday, August 3, 2010

Using Hydraflow Express for Channel Calculations

Source: http://bimontherocks.typepad.com/

I was working through a predevelopment time of concentration yesterday using Civil 3D and Autodesk SSA, and I needed a cross sectional area and wetted perimeter for a natural channel.

In Civil 3D, I had my TC path drawn, and using the terrain model, I could see where I entered into channel flow. I used some quick profiles across the channel, some surface analysis and slope arrows to help me get my bearings. 

Then, I made a short alignment across a representative section of the channel. You could make as many as you’d like.
By making an alignment, I could make a profile and profile view as well as labels. I traced the existing ground profile with a layout profile to get more crisp tangent lines, then used profile labels for 1:Z slopes. I used Seth’s trick of using line labels as dimensions to give me some of the other pieces I needed to calc the CSA and WP.
Then, I launched Hydraflow Express from the Analyze tab in Civil 3D.
It was easy to enter the bits I needed for the calculation thanks to my profile view labeling. I could have added a few more labels- such as invert elevation, etc. if I wanted to get more information from the calculator.
As you experiment with Autodesk SSA, don’t forget about the tools in Hydraflow Express. There is no wrong way to use the tools in your toolbox- find the combination that gets you what you need for your design.

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