That process which Moini mentioned will prepare the text to be split up into the different layers. But I'm not clear if you want the text to be joined with the contour lines, or just on top of the lines. If the text is to be on top of the lines, the text pieces will be separate paths.
If you want the contour lines joined with the text, so that the text is cut out as part of the same contour line, some more editing will be needed.