Topographic profiles with the highest slope
Hi everybody,
First, sorry for my english, it's not perfect and i'll try to do my best here
I'm actually working on a project in Madagascar and i have a lot of work do to with rockslide. Some place might be concern by this phenom and i'd like to work on Arcgis to calculate the propagation of blocks from a cliff in my area.
The idea is "simple" and i've done it (in the past) on Mapinfo using topographic profile (with a raster) and then priting the profile and working on it. I'd like to do this on Arcgis with the software if it's possible.
I have a DTM and a raster with the slopes of my area. I have some cliffs (materialized by a polylign for example) and i'll like to draw a topographic profile in the highest slope. This is relatively easy i think as there is a tool in arcmap to draw this directly.
BUT, i'd like to draw a profile who start from the cliff, and with a certain angle (°). The angle is from an imaginary horizontal line at the top of the cliff. I would like to know where the line (from the top of the cliff) intersect the ground.
An image is better to illustrate (see bellow).
Drawing the topographic profile with the highest slope is possible for sure (even if i'm not sure how arcgis draw this profil)...
This procedure is doable is Arcscène (in 3D) also and it might help me to work with that.
Maybe it's possible. If someone have any leeds, clues, that'd be great
I would really much appreciate some help here
Have a nice evening
Sylvain
The second line just needs to be a fixed horizontal distance from your cliff so you can determine the elevation based on the angle (see image - I hope that helps a little and I haven't made any math mistakes). Then after you have your two surfaces (ground surface and slope surface) you can show both on a profile graph or use raster calculator to compare the ground surface to the slope surface to get the line of intersection.
There is likely an easier way, but this method worked for me.
I might not be understanding the problem completely here, but it occurs to me that another approach you might take is to use Viewshed in map view. You could create a line along the top of your landslide scarp and then define angles to bracket the search area on the raster below, as if you were standing on the bluff and using an inclinometer. See the attached image. The power of this method is that you could do zonal statistics on an intersection of the visible areas with your slope map. You could also vectorize this raster and convert it to cross section features. That should give the same result as starting with a surface profile in cross section view and then drawing a line with your angle of declination to find the intersection on the surface below the bluff.
