Farm Tile Modeling

[HemM]

Hello, I need help modeling a 100 Acre farm that is tiled. The goal is to size a culvert, downstream, for a flood event. I'm stuck on how to model the farm area. Flow goes overland but also infiltrates into the tiles, which all routes to a ditch downstream, and to the culvert.

Thoughts-

Storage:
underground pipe volume

Outlets:
- Main tile outlets to ditch -device 1
- Tiles that feed into the main line - device 2 (feeds to 1)
- Infiltration (0.5in/hr) - device 3 (feeds to 2)
- How would I model the overland flow or separate that from the infiltration outlet?

 

[psmart]

Obviously, there will be a runoff component, but the presence of the tiles means that the soil will not exhibit standard runoff behavior as predicted by the SCS method, so standard CN values will not apply. You will also have some storage and time lag as the water penetrates the soil to the tile. Again, this flow regime is beyond the scope of traditional runoff and routing calculations. If you know how the system will behave I can help you model that behavior, but there are too many unknowns to predict the behavior with any certainty. Perhaps you can do a rough runoff calculation for surface runoff, added to a constant flow from the tiles.

 

[HemM]

Obviously, there will be a runoff component, but the presence of the tiles means that the soil will not exhibit standard runoff behavior as predicted by the SCS method, so standard CN values will not apply. You will also have some storage and time lag as the water penetrates the soil to the tile. Again, this flow regime is beyond the scope of traditional runoff and routing calculations. If you know how the system will behave I can help you model that behavior, but there are too many unknowns to predict the behavior with any certainty. Perhaps you can do a rough runoff calculation for surface runoff, added to a constant flow from the tiles.

Thanks for the tips and fast reply. I'm going to think how best to proceed... probably assume no infiltration and model the culvert off a larger conveyance.