Planation Stream Piracy. 257 
portion of the parent stream valley at the Cut-off Col is 595 feet above sea 
level. The col is thus 80 feet higher than the valley-flat of Salt Creek. 
But the col is at present some distance west of the place where the piracy 
was effected, and in that distance the parent stream had a fall of 10 to 15 
feet. Thus, Upper Cut-off Creek at the time it was diverted was perched 
90 to 95 feet above Salt Creek flood-plain. At the time of diversion the 
waters of Upper Cut-off Creek entered Salt Creek valley over a fall 90 to 
95 feet high. This fall may have endured for some time, but the nature 
of the rock is such that the fall could not have persisted. The rocks are 
easily eroded and weathered, and there are few or no ledges of superior 
hardness. The correction of this peculiar gradient of the diverted stream 
has deeply entrenched the valley, having cut it some 90 to 95 feet deeper 
than the valley of the parent stream. Thus the Upper Cut-off Creek drain- 
age basin furnishes an excellent example of a stream basin that has been 
statically rejuvenated 
Migration of the Cut-Off Col—At the time that the parent Cut-off stream 
was divided into two parts by the lateral planation of Salt Creek the 
divide between the two parts was probably immediately west of the place 
where the cut-off was effected. The rejuvenation of the upper stream 
basin was followed by its intrenchment far below the former fairly well 
graded valley-level. The tributary stream which comes in from the south 
near Phillips School was probably for a time a tributary to Lower Cut- 
off Creek. But the rejuvenation brought about by the piracy gave rise to 
a condition favorable for normal headward erosion piracy. Rainwash 
and gullying on the west brought about the capture of the somewhat slug- 
gish stream from the south, thereby enlarging the basin of Upper Cut-off 
Creek. Headward erosion continued westward down the course of the par- 
ent stream, and the small ravines on either side were captured in succes- 
sion. The divide has now migrated by this headward erosion process about 
one-fourth mile west of its original position at the time the planation piracy 
Fig. 38. View directly across the “Cut-off Col’ from the south. The small 
ravine at the left is the very head of Lower Cut-off Creek. 
2 Sea Malott, Static Rejuvenation, Science, New Series, Vol. LII, No. 1338, Aug. 
