This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

How to accurately model a culvert in PondPack V8i

Hello all,

I am in the process of refining some of my models and I was wondering what is the most accurate way of modeling a typical culvert that diverts a stream under a road?

For example, lets say I have Catchment A that flows into a stream. The stream then flows south for 100' to a large culvert. The culvert goes under the road for 50' and at this point, Catchment B flows into the stream. The stream then continues for another 100' before coming to an outfall.

Personally, I would have Catchment A flow to a Junction (say J1), model the stream as a conduit for 100' from J1 to a new junction (J2) right before the Culvert. I would then model the Culvert as a new Conduit traveling for 50' from J2 to J3. Then I would add Catchment B and have it flow to J3. Finally, I would connect J3 with the outfall using another 100' long conduit modeled as the stream.

However, I hesitate to do this, because I know that conduits are supposed to represent open channels and not pipes. And since the Culvert is in theory "piping" the stream under the road, it is not an open channel.


I suppose you could also just do all that mumbo jumbo above within the travel time calculations of each catchment. In which case, there would be no need to model anything I mentioned above, besides the two catchments flowing to the same outfall.

So to sum everything up, which is the better method of modeling such a scenario? Model the stream then culvert, then the stream again, or just include all that in the travel times of the individual catchments?

Thanks.

TimZ

Parents
  • Hello TimZ,

    It is possible to model circular conduits in PondPack, however these only attenuate flow. If you are not concerned with entrance losses for culvert and if the culvert will never flow full, you could use circular channel link type.

    However, if you want to size the culvert or check for overtopping, the circular channel would not be sufficient for your modeling case. The optimal solution would be to use CivilStorm or SewerGEMS, which are fully dynamic programs that will model the transition from open channel to culvert and back to open channel without issue.

    There are options that you can try. If you are trying to size the culvert, you could model the system with the circular channel to get the attenuated hydrograph. With this hydrograph, you could use CulvertMaster to check the culvert size based on the peak flow.

    If you want to model this completely in PondPack, you could try the following. From the upstream stream, you would end this with an outfall. The outfall would drain into a no-volume pond. This pond would have an pond out node with a composite outlet structure though. The outlet structure would include the culvert you want to model. This outlet structure would be connected to the next junction, then continue to the next stream. Basically, the no volume pond-pond outlet-pond outlet structure combination would represent the culvert in the system. While a roundabout way of modeling it, it takes advantage of the HDS-5 culvert calculations used with the culverts in the pond outlet structures.

    Information related to modeling conduits that may become pressurized in PondPack can be found at the following link: http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/17037.modeling-closed-or-pressurized-pipes-in-pondpack

    Regards,
    Scott
Reply
  • Hello TimZ,

    It is possible to model circular conduits in PondPack, however these only attenuate flow. If you are not concerned with entrance losses for culvert and if the culvert will never flow full, you could use circular channel link type.

    However, if you want to size the culvert or check for overtopping, the circular channel would not be sufficient for your modeling case. The optimal solution would be to use CivilStorm or SewerGEMS, which are fully dynamic programs that will model the transition from open channel to culvert and back to open channel without issue.

    There are options that you can try. If you are trying to size the culvert, you could model the system with the circular channel to get the attenuated hydrograph. With this hydrograph, you could use CulvertMaster to check the culvert size based on the peak flow.

    If you want to model this completely in PondPack, you could try the following. From the upstream stream, you would end this with an outfall. The outfall would drain into a no-volume pond. This pond would have an pond out node with a composite outlet structure though. The outlet structure would include the culvert you want to model. This outlet structure would be connected to the next junction, then continue to the next stream. Basically, the no volume pond-pond outlet-pond outlet structure combination would represent the culvert in the system. While a roundabout way of modeling it, it takes advantage of the HDS-5 culvert calculations used with the culverts in the pond outlet structures.

    Information related to modeling conduits that may become pressurized in PondPack can be found at the following link: http://communities.bentley.com/products/hydraulics___hydrology/w/hydraulics_and_hydrology__wiki/17037.modeling-closed-or-pressurized-pipes-in-pondpack

    Regards,
    Scott
Children
No Data