How to use ENVImet- Grasshopper build a sink area?

[Cliff Wang]

Hi,everyone
I use Rhino-Grasshopper to build my city model.There are two city rivers pass through my study area. Rivers and their riverbank are sink space in city.Maybe 2-3 meter lower than ground of city. In Rhino, I made a surface of study area to detect my model.It worked, but a little problem was that it could't detect area of sink area(ex. rivers).Sink area show nothing on SPACES.How can I solve this problem?
Thank you for your help!

[Tim]

Hi,

So, you expected to have a lower terrain in that area, right? Maybe, the resolution is too coarse to see such small differences in the terrain?

Best regards,
Tim