I was asked to identify concentrated flow paths on a terrain but specifically where the flowline exceeds a certain slope, for evaluating erosion potential. I am familiar (I think) with the Analyze Trace Slope tool, but would like to find a way to efficiently isolate parts of flowlines that exceed the specified slope. Any creative ideas?
Can you use a thematic display style that colors triangles from the surface if they exceed your slope? I have done something similar in Civil 3D for fill slopes and ped ramp design, but haven't ever tried in GEOPAK or ORD.
That's a good thought and as part of this I need to highlight slope areas that exceed 3:1 so thematic slope display works well for that. But if there's a ditch with say 6:1 side slopes on a 5% grade, I need to identify that even though the slopes are not a concern, the flowline of the ditch is steep enough to need to be looked at for erosion protection due to the concentrated flow. If it is a constructed ditch with a known profile that's one thing but it seems like a lot of areas of concern are where the fill limits run down into a ravine. So what I am thinking of is some way to highlight just slope of flowlines as opposed to areas.
Chris, I see what you are getting at here. I was just thinking that the edges of the triangle would be at least so it would at least weed out some of the places you wouldn't need to check, but at least with something like a 5% grade you'll get a lot highlighted areas.
I was thinking you could you use the Analyze Trace Slope tool. Turn the resultant line into a civil feature and create a surface profile. From there you could at least visualize the path your interested in and measure slopes from the profile view. Only catch is I can't seem to find a clean way to drop the line work from the trace slope. Depending on how long your areas are for evaluation, creating a quick horizontal geometry by PI and sampling the surface does let you visualize it. From there I was able to draw a short line at my slope of concern and just move it down the alignment to identify areas that are close to that to examine. Hope that all makes sense, if not let me know I and will try and explain it better. An interesting question, it's been to spend a little time thinking about it...back to work.
Due to time constraints what I wound up doing was using the Geopak DTM Tools > Analysis > Sump Lines to draw all the possible flow paths (trace slope works too but more clicking), and then looked visually for any places where flow paths crossed more than two contour lines in 100 feet (for a 2% slope). I drew a 100 foot diameter circle and moved it around, which helped me train my eyes to see the denser contour areas. Then I create-complex-chained the sump lines that qualified. I had to cover 2.5 miles of hilly terrain so I suspected that creating and opening the profiles I would run out of time. Thanks for the insights! Mission accomplished.
Nice process. I do have concern about the number of times that the "solution" is to go back to tools in GEOPAK or InRoads SS2, especially since those tools don't move forward into ORD.