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I have the boundaries and centerline of a river.

The Thalweg line defines the deepest elevation of a watercourse (see Image taken from Google). I do not have accurate enough bathymetry or Digital Elevation Models to determine the proper deepest elevation of a river channel.

I would like to know if it is possible determine the Thalweg line of the river without the bathmetry?

enter image description here

It looks like the Thalweg line follows a predictable pattern where it hugs the outside curve of a river when it meanders and is in the center of the river with it is straight.

I am using ArcGIS 10.1 with all licenses available, and I am familiar with python.

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    The thalweg is going to be closer to the outside of the bend in a meander, but its exact location can vary. The straight line segments are the bigger issue, where the thalweg can meander considerably (which ultimately creates new meanders in the river). Cross-section stations would help considerably if you can get those, otherwise it is not really a solvable problem with just centerline and boundary. Feb 2 '16 at 18:56
  • I am unable to get any cross-section stations. I am more concerned about determining the outside curve of a river using the Thalweg (Highest chance of erosion) than where it falls on a straight section.
    – JC11
    Feb 2 '16 at 19:18
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    @JC11 if position of outside curve is main objective you might want to calculate angles at each vertex
    – FelixIP
    Feb 2 '16 at 19:22
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You don't really give a scale at which you are working at? The entire Amazon or a section of a river as suggested by the image above? Without Bathemetry data or cross sections I would imagine computing a Thalweg would be very difficult, if not impossible (personally never done it). Also what about the geology, bedrock outcrops would constrain the rivers planform.

Just looking at the image I started thinking about radius of curvature as a possible way of measuring erosion rates? This article on Grays River talks about radius of curvature. A quick google search will throw up other articles/journal papers.

If the extent of your data is really what is in your image then you can simply draw the circles by hand?

Just an idea?

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