Watershed Analysis

[Anonymous]

Is there a way to make the Watershed Analysis in Civil 3D take less time w/o piece mealing it w/boundaries? Simplifying the surface does nothing. My surface has a ton of data and its over several hundred acres at least. I have a feeling the program is looking at a cross section like this 1.0' - 1.01' - 1.0' and treating it like a continental dvidie. I tried using the function to merge watersheds with hieght differential smaller than a certain range but that didn't help the process take any less time. Even with that and a boundary in place im still getting a TON of watersheds.

[fcernst]

Yes, this has been an issue since LDD 1. How could this be better if the height differential doesn't seem to ever work for us?

Could the software take an initial stab at it, and then ask the engineer, : "How does this look?', with a Yes or No dialog box..

Then if the engineer says 'No", the software takes another stab at it, decreasing the number of Watersheds by some percentage the engineer can previously set, say 10% per iteration for instance.  Then when things start looking more like the amount of basin discretization the engineer wants for the site, the engineer says "Yes", and we can be done.

[Neilw_05]

According to the README for 2013 SP1:

Surface

• Watershed analysis performance on DEM surfaces has been improved.
• The Drape Image command no longer results in a reversed image when hardware acceleration is enabled.
• The stability of the Level of Detail command has been improved.
• The stability of the Resolve Crossing Breaklines command has been improved.

Perhaps it will help in your situation. You should review forum posts about issues with the service pack before installing it.

[Anonymous]

Well, I guess it could use another service pack because it still needs drastic improvement to even be useable.

[fcernst]

I just did a Watershed analysis on a 30 acre existing topo I have. It would have been desired  to have about 6 or 7 watersheds for existing condition analysis to determine historical offsite release rates, and potential placement of new proposed detention ponds.

Civil 3D created 92 watersheds without "Merge adjacent watershed boundaries" on, and 31 watersheds with it checked on.

The problem is with the "Boundary Segment" type of Watershed, it still created 26 of them with "Merge adjacent watershed boundaries" checked on. Some are only  20 sqft in size, etc...

It's helpful to see the TIN fully discretized like this at first, as a start, so the modeler can check the TIN response to the data provided  to the C3D surface algorithm. However we are not done yet!  

We need a tool for the engineer to aggregate the basins after that, as the engineer sees fit.

We need to have a "Aggregate Watersheds" by selection tool.  To be able to Window Select neighboring watersheds for aggregation into one watershed.

Then I could easily aggregate these Boundary Segment watersheds into useful watershed objects per my engineering judgement that involves hydrologic and hydraulic analysis, drainage plan requirements, specific project requirements, offsite implications, etc...

[Neilw_05]

I totally agree with all you say here. Perhaps a post to the wishes forum would be in order.

[Anonymous]

Great idea! I bet with all the talented programmers out there this could be done.

[Neilw_05]

Having not worked with Watershed styles much I am finding a few other things that need to be addressed.

1) Inability to identify basins either with an inquiry tool or tool tips. Nor is there any graphical feedback to know which basin is selected when picking a record in the table in Prospector.

2) Inability to modify basin display attributes (hatch style, color, etc.) by selecting mulitiple rows. I think this would be better handled by the style with the option to apply overrides vs. it being independent as it is now

3) Edits to the Watershed style does not update the surface. The analysis has to be re-applied after changing the style (note comment 2)

I am sure the list will grow