Thursday, September 9, 2010

GCNP Boundary: H I: The Shivwits (revised 11 Sep 2010) ADDITION 27 SEP 2010

The lands defined by the three boundary segments H, I, and J were for the most part from Lake Mead NRA. Had the logical step been taken, the Park boundary would have been drawn to put all of LMNRA east of the Grand Wash Cliffs in the Park. However, significant parts of these Canyon features -- the Shivwits Plateau, Parashant-Andrus Canyon, Whitmore Canyon and vicinity -- were not added to the Park. Strangely, the administration of the non-GCNP Canyon lands was left with LMNRA in Boulder City. That complexity has been compounded by the 1999 proclamation of Grand Canyon - Parashant National Monument, divided between BLM in St George Utah and LMNRA, although the NPS ranger for that area is headquartered at the BLM office. Just to make life even more confounding, the northwestern half of the GC-PNM has nothing to do with the interpretation and protection of the Grand Canyon. Nor with the Parashant, for that matter.

Here is the official 1975 Act map. From the west, segment H is the straight east-west line followed by the bump. Segment I is the wiggly stuff trying to follow a rim. J is the east end including that horn that sticks up northwest below "Boundary". But there is a problem. 
Here is a terrain courtesy of Google maps, to show the problem. We need to pick up the boundary at the river R, carry it up through the topography to the mid-level SANUP plateau, a feature similar to the Esplanade and the Tonto Platform, and finally walk along, keeping the Grand Canyon drainages to our right until we get to an appropriate point to scramble up to the ultimate plateau, the SHIVWITS, where segment I starts, after which we will go along the uppermost rim, over to the Shivwits' east side, where we drop down to do segment J (not on this map).
So far there are two solutions. What the official map indicates is the blue line on the detail map below.

To follow this line, go two miles north from the river crossing measuring from the south bank. From the official map, the start seems to be from the south line of T32N. However, on the BLM map, that south line is a mile south of the river. I suspect NPS used a pre-survey township grid base, while the BLM now uses the surveyed lines. It may not matter as long as the distance is two miles from the south bank, as the official map shows.
When you have walked the two miles, you find yourself, unintentionally I think, right in the middle of the Pearce Canyon drainage. Turn right, and unheeding of the wash's turns, scramble straight up due east. You are now on the Sanup plateau. Wander off not quite northeast toward the southern edge of that cliff above you (that is Snap Point), float up it, and plant your flag. You are now on the Shivwits level, and we can follow the rim into Segment I. 

It is quite clear that the official map's solution, like the area included in segment G, includes too much; land that is not part of the Canyon topographically--Pearce Canyon drains west from the Grand Wash Cliffs. It may be that this line comes from a map we generated in the late 1960's, which also included too much in this area and was never refined. And that is the case, as I explain in the post about Segment G. I am sorry I did not do better 40 years ago.
 So I planted some red crosses to show how it would go if were a more pure Canyon line, starting across the river from the ridge of the Grand Wash Cliffs, up ENE to a piece of the Sanup, and then strolling around keeping the Pearce Canyon drainage to the left and the Canyon's inner gorge to the right, ending up at the southern end of Fort Garret Point (Ft. G. p), and then up onto the Shivwits. Again, another piece of work for the future.

Although I have no documentation, I do remember talking to NPS-DSC staff who were checking out the boundary after the Park Act was passed. They had been out to Snap Point and it is possible that they provided information for a placing of the official line. In any case, I do have copies of very large-scale LMNRA maps revised by NPS-DSC to show the boundary as of May 1975, and they seem a reasonable realization for this segment, H, of the Act's map, as well as for I, the Shivwits rim. 

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