Planation Stream Piracy. '17u 



IKirtioii (if tlic iiiiioiif stream valley at the Cnt-ofT Col is HOrt foct almvo sea 

 lc\cl. Tlic c.I is thus SO feet higher than the valley-flat of Salt (M-eek. 

 I'.iit tiie col is at present some distance west of the place where tlic jaracy 

 was etfeetod. and in that distance the parent stream had a r.ill of 10 to 1," 

 feet. Thus. Upper Cut-off Creek at the time it was diverted was jicrched 

 !M) to 95 feet ahove Salt Creek flood-plain. At the time of divcisioii tiie 

 waters of Upper Cut-off Creek entered Salt Creek valley over a fall !m> to 

 it") feet high. This fall may have endured for some time, hut 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 iRH-uliar gradient of tlie diverted stream 

 has deei)ly entrenched the valley, having cut it some 90 to 95 feet deeper 

 Ilia II the valley of the parent stream. Thus the Upper Cut-off Creek drain- 

 age hasin furni.shes an excellent example of a stream basin that has been 

 statically rejuvenated.* 



Migmiion of the Cuf-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 \<'as probaldy 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. Tiie 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 b.v the piracy gave rise to 

 a condition favorable fin- normal beadward 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 i)ositioti at the time the planation piracy 



Fig. 3. 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. 



"C. A. Malott, Static RcjuvcUiition, Scionop, Xew Series, Vol. LIT. N... i:W8, Aug. 

 20, 1920. 



