OVERFLOW AND PIRACY (possibly superimposition)

"Topographic control of transverse drainage incision into
 a low saddle across the bedrock high"

  Unlike for antecedence and superimposition, both overflow and piracy transverse drainages are strongly controlled by the topography of the bedrock high.  More specifically, both a drainage spilling across a divide (the upper image) during piracy or a lake overflowing across a basin rim (the lower image) will do so at a low saddle in the bedrock high.  Overflow will always take place at the lowest saddle across the bedrock high.  Piracy, however, doesn't necessarily have to spill across the "lowest" saddle, but will occur at a low saddle in close proximity to the pirated drainage.  One last caveat, superimposed drainages can develop across low saddles if the bedrock high is only partially buried by the covermass.