Culvert design?

[jy3050]

Dose StormNet have a function for culvert pipe design? what is the modeling precedure for using StormNet?

[Chris Maeder]

Note that it is very easy to model a culvert and roadway overflow in StormNET.

Define a junction at the upstream end and downstream end of the culvert. Then, define a pipe link between the two nodes representing the culvert. To account for storage upstream of the culvert (from backwater), you can change the upstream junction to a storage node (detention pond). To model the roadway overflow, define another link (open channel) between the two nodes representing the culvert. Obviously, you will need to define invert elevations, etc.

Make certain to account for inlet conditions (inlet loss coefficient) for the headwall structure at the culvert. You define this for the culvert link. A value of 0.5 is typical, but it can go as high as 0.7-0.9 and as low as 0.2. A higher value means there is more momentum loss, a lower value is less momentum loss. Generally the outlet conditions (outlet loss coefficient) for culverts is assumed to be 1.0 (all momentum is lost).

Note that we plan on adding the FHWA culvert nomograph routines (HY8) to future version of StormNET. However, the limitations with HY8 is that it cannot model flow reversals. I'm still trying to figure out how we will handle these cases with HY8.

If you continue to face problems or have questions, feel free to call our technical support team at 1-800-488-4775.

Sincerely,

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

[stevej00]

Chris, Do you have a screen shot of this schematic ?

(sorry for bring up an old post)

[Chris Maeder]

I have attached a StormNET example model that illustrates flow backing up behind a roadway crossing, where culvert flow and road overflow occurs.

The storage area upstream of the culvert is represented as a dentention pond, although in reality this is simply the ponded storage area for water trying to flow through a culvert that is sized to small. Since the culvert is too small, you will also observe road oveflow.

This example model will be included in the next release of StormNET as an example model.