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drtees203 post(s) |
Some jurisidictions require that a critical area buffer that extends onto a steep slope be measured from the top-of-slope, or the point on the landscape where the slope is less than a certain percentage and extending for a minimum distance. The Display Options dialog in M8 allows one to specifiy particular colors for specific slopes. However, I would like to be able to define a line on the landscape where the slope is a certain percentage or less over a minimum distance. My current project involves a stream in a deep, artificial channel. The remainder of the site is relatively flat. The top-of-slope I am trying to define as a line is the point where the percent slope of the artificial channel is less than 5 percent. The solution I used involved applying the slope transform to the surface subset, using the Display Options menu to provide the color separation parameters, copying and saving the resulting surface as an image, and then using the Trace function to create a broad area for the color that represented a slope range between 0 and 5. I am figuring that there is a much more elegant solution that I am not seeing in the documentation for M8. I have attached an M8 map file with a subset of LIDAR data containing the stream channel. I appreciate any insights. Attachments: Top of Slope.map
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That sounds good. An alternative would be to make a single contour area (areas below heights: 5) from the slope surface. If you need a line, you could create a single contour line at 5° slope. (Decompose the contour after creation if you want to delete some parts.)
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I've found that this method creates a lot of noise on detailed slope rasters. Consider smoothing out the slope raster a bit first in the Transform dialog. You can play with the second variable a bit to vary the smoothing. Avgvalue([DEM], 4)
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