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enter image description here

I have a series of shapefiles using polylines to represent the hydro network of a region. As you can see in the picture, these polylines go into great detail. These polylines are very segmented even though it seems they run in one continuous line.

My goal is to isolate specific rivers from these shapefiles and make each rivers into one polyline. I have a list of which rivers I am targeting.

Most likely, these rivers would take the longest paths in these shapefiles. How can I determine longest path of segmented polylines? Once I find the longest path I can determine which river it represented and separate it into its own shapefile.

I need to data calculate sinuosity of rivers.

I'm using ArcGIS 10.1 with an ArcInfo license.

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    i might ask about the source of the data - govt-provided hydrography layers usually consist of individual arcs at the whim of the original digitizers/as needed for type/duration attribution, or perhaps aggregated confluence-to-confluence into reaches, but also include some attribute such as name or ID that can be used to aggregate them into culturally-recognized 'rivers'. lacking any of that, you might want to look at the RivEX tool - www.rivex.co.uk
    – MC5
    Nov 27 '13 at 19:18
  • What precisely do you mean by "segmented"? Does that mean what looks like a connected polyline on the map often is represented by two or more separate features? Also, do you have the original DEM from which these data were derived?
    – whuber
    Nov 27 '13 at 19:48
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    The polylines follow the rivers I want to analyze, but they are not one single polyline following the river. They are separated into many polylines, this is what I mean by segmented. The data is government provided as a feature in a gdb, but I converted it to one shapefile by clipping and merging it to fit the study area. I do not have the original DEM.
    – JC11
    Nov 27 '13 at 20:06
  • Are there any attributes associated with the polylines that can be used to merge features? Often layers of this type will contain a 'stream order' attribute.
    – Radar
    Nov 27 '13 at 20:29
  • RivEX can automate the extraction of the main channel from a vector network for each catchment, especially if the network was derived from a DEM. Your sample image shows a coastline, that would have to be removed first. If you wanted main channels for sub-catchments then better off using the Source ID which it can calculate. You can download a demo to see how it functions.
    – Hornbydd
    Nov 27 '13 at 22:18