Realistic ground profile for swales
This is a flaw that's been going since MicroDrainage, but when you change the type of a connection from a pipe to an open channel, like a swale, there's no information at all provided about the actual size of that feature.
I had one come in the other day, only attenuation on the whole site was in a swale. Parameters for the swale has been set 0.5m base width, 1:3 side slopes, Mannings n 0.03, everything normal and okay with this, right?
But the manholes at the top and bottom of the link that had been turned into the swale were around 1.6m deep. So the real width of that feature was over 10m wide. Even though the corridor that had been allowed for the swale was a good size, between 3-4m, it was nowhere near accommodating the actual feature.
This hadn't been spotted because InfoDrainage doesn't say it anywhere. When you model a link in this way, it should ask for the top width rather than the base width, or it should as an absolute minimum write the full or maximum width it assumes for the feature somewhere where it is clear to see in the connections review data.
Lucy Moxon
shared this idea
Thank you for the suggestion and thanks to those who commented and voted.
If you try to build your swales using the SWCs rather than converting links to swales, you will see that you can start from the top area and go down (1:3) or you can start from the bottom and go up (1:3).
Does the above address your suggestion? I'd be interested to hear your thoughts once you try it.