If watercourse alignments have been imported (GIS >> Streams) then this data is likely to be 2D. Thus in order to rasterise this information into the DEM linear interpolation is undertaken between intersected contour lines along each stream alignment. This algorithm will piece together complete stream alignments from a network of stream segments and process each in turn from the main stream to last tributary. The watercourse interpolation algorithm is described in more detail in the algorithm section.
