Creating Buffer of specific area using QGIS?

Question

I am trying to create a buffer which would include only the Mediterranean coast of Spain (excluding borders), running from the south western extremity close to Portugal, to the north eastern extremity close to France. Is there a way to to this based on the map I have?

Answer 1

You need to do the following:

• Convert your polygons to lines using Convert polygons to lines tool from Processing toolbox -> Saga -> Vector line tools -> Convert polygons to lines
• Start editing the line shapefile
• Use Split Features tool, shown at the image below, to split the line boundary at both sides of the coastal region, and save the edits

• Select the line along the coast and use Buffer tool to buffer only that line.