PIRACY

"Possible different paleo-flow direction for the transverse drainage
 upstream of the bedrock high"

  For piracy to work, the captured drainage must have flown in some other direction prior to capture.  To suspect piracy, a paleo-flow direction must exist upstream of the bedrock high and should persist long after transverse drainage incision.  The upper image shows a paleo-flow direction of a simulated pirated transverse drainage in a physical model.  Granite Park Canyon, a tributary to Grand Canyon, provides a field example of a paleo-flow direction and shown in the lower image.  Base-level fall associated with Grand Canyon incision allowed the drainage divide of the canyon rim to retreat and capture Granite Park Wash.