# Modelling stream in 3D based on known depths across it using ArcGIS Desktop?

I have an excel spreadsheet that contains the elevations across the profile of a stream. I was wondering how to model this in 3-d. Basically there are 6 monitoring stations that are within a stream. I know the elevation of each bank, the slope of each bank, and the depth across the stream at each location. The depth was measured every 20cm across the profile of the stream. eg/ 0.35m across/depth 0.4m, 0.55m across/depth 0.95m, etc. I know that because there are only 6 stations, the result will probably be very blocky, but there are ways to fix that. Basically, I am just looking for somewhere to start. Like I said, I am pretty sure I have all of the pertinent information in an excel spreadsheet, just need to know how to get going.

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You will probably need to create a 3D breakline of the water edge from the data you have, then using the points (you may convert there to point features with a Z value) create a TIN surface from the points and the breaklines.

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Did that work? You mentioned you also know the slope of the bank. If you can calculate the XYZ points on the bank using the slope and distance from the water edge, you could also model the bank surrounding the stream. Create a 3D breakline for the bank perimeter and use the water edge breakline to create a TIN surface of the bank; to remove the stream area, delete it using the "stream" domain (polygon). – Jakub Nov 24 '10 at 14:18
Ya it worked. But the only thing is, the TIN elevation values (filled in areas) are all distorted. The profile of the stream looks alright (viewing just the hard breakline) but the spaces in between are all messed up. The slope of the bank is... estimated at best. So I don't think that creating a TIN from the estimated values will work out so well. Right now, when I visualize in ArcScene, all I can see is the "profile" of the stream, without any polygons connecting the nodes. How would I go about adding the sides of the stream, so as to not have just an outline of the profile? – Andrew Nov 24 '10 at 16:41
And by sides of the stream, I mean the bottom that would be underwater. – Andrew Nov 24 '10 at 16:42
Create the TIN using all the points (with Z values) as well as the breakline. You might need to trim (hard clip) the "convex hull" excess triangulation by a polygon that is the area of the stream bed. – Jakub Nov 24 '10 at 17:42

So you want to create a 3d cross-section of the stream at that one location? Do you have any arc extensions? If not you might try the etsurface from ianko.

Did you see this other question?

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Ya, I have 3-d analyst. Basically, any directions as to where to start would be helpful. ie/ do I have to create a 3-d line, or just use the points and interpolate based on a z-field? The depths we are looking at here are very small (less than a m) but can be exaggerated out anyways, I just need the direction of where to start. – Andrew Nov 23 '10 at 21:17
I'm not sure you will be able to generate a profile using analyst. You would first need a surface to derive the profile from. Are you working with a DEM also? Do you just want a single profile plot? If that is all I had and all I needed I would just draw it in a CAD. – Brad Nesom Nov 23 '10 at 21:26
Does it matter if I have the height of the water? COuld I possibly make a polygon layer, set the elevation of this layer at the water level, and extrude downwards the depths of each of the points across the stream? Does that make sense to anyone? I know there is a way to do it, because I have done it before, I just can't remember how to start. – Andrew Nov 23 '10 at 22:01
I'm not sure I understand what you want to end up with. If you are using arcgis, viewing the data is going to require some 3d. If you just need a simple profile all that seems like a lot of work. You can use argis lke a CAD and just draw your profile laid down on "the ground". – Brad Nesom Nov 23 '10 at 22:35