I converted a raster to polygon, after converting polygon to lines I have one line of the channel of a river which border a river. But I need to split this line in two lines: left border and right border of the river.


How can I split this line in two lines, left border and right border?

  • I was just wondering regarding the output that you would like to achieve, can you please describe it? Should it be two separate shapefiles, or the same but with some special attribute which indicates the location of the bank etc. Am I correctly perceive that the upper part of your polyline is enclosed but the bottom is opened? How many of such objects do you have in your project? – Taras Apr 13 '19 at 20:24
  • You may try using SAGA GIS Module Split Lines at Points, you just need to add a point on the top of your river and proceed with the algorithm in the Processing Toolbox. – Taras Apr 13 '19 at 20:40
  • 1
    Alternatively, you may be using the native QGIS tool "Split Features", see this threat How to Split Features in QGIS? – Taras Apr 13 '19 at 20:44
  • There are also several solutions but applied to the river as a polygon, check Creating centerline of a river with QGIS? and Finding centrelines from polygons in QGIS?. – Taras Apr 14 '19 at 11:55

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