The document analyzes potential routes taken by the Dunn-Howland party as they left the Powell expedition at Separation Canyon and traveled north towards Mormon settlements. GIS analysis using cost distance, least cost path, and viewshed tools modeled three possible routes. Route 1, which followed the eastern fork of Separation Canyon and passed Blue Mountain and Ambush Water Pockets, aligned best with historical accounts and had good visibility of landmarks. This route, and a similar route derived from a hiking cost model, were determined to be the most plausible paths taken by the Dunn-Howland party.

1. Mapping the Dunn – Howland Journey
out of the Grand Canyon with GIS
GIS 5100 – GIS Applications
Elizabeth Roycraft

2. 1
Introduction
In the summer of 1869 John Wesley Powell set out with a group of men on a scientific expedition to map
the then unknown portions of the Colorado River. It was the first successful documented navigation of
the river through the Grand Canyon (Stegner 1953). Hardships occurred during that first journey, most
notably the loss of much of the expedition's food supplies relatively early on during the trip (Belshaw
1979, Stegner 1953). As the river became rougher with seemingly no end in sight, morale amongst the
crew dropped and ultimately three men decided to leave the expedition – these men were William (Bill)
Dunn, Oramel Gass (O.G.) Howland, and Seneca Howland (Belshaw 1979, Stegner 1953).
The departure of the Dunn – Howland party from the Powell expedition took place at Separation Canyon
on August 28, 1869. Their destination was ultimately to be the Mormon settlements north of the
confluence of the Virgin and Colorado Rivers (Belshaw 1979, Stegner 1953). Ironically, the Powell
expedition reached their intended destination at the Grand Wash Cliffs only two days after the Dunn –
Howland party had left them (Stegner 1953); Dunn and the Howland brothers did not fare as well. A few
days after their departure from the Colorado River they were murdered somewhere on the high plateau
above the north rim of the Grand Canyon. Speculation abounds as to whether they were murdered by a
local Shivwits tribe (Belshaw 1979, Compton 2013, Dobyns & Euler 1980, Stegner 1953) or by Mormon
settlers afraid of potential informants revealing their location to United States federal authorities
(Compton 2013, Stegner 1953). As their bodies were never found and the only evidence of their murder
was through reports from Mormon settlers, the exact sequence of events leading to their eventual
disappearance may never be known.
While it may not be possible to solve a nearly 150-year-old murder, there is the potential at least to
discover the answer to another minor mystery surrounding the Dunn – Howland party: how did they get
up onto the high plateau above the north rim of the Colorado River? There is some evidence hinting
strongly that the Dunn – Howland party not only made it out of Separation Canyon onto the high plateau
above, but that they also had made one definite stop at Mt. Dellenbaugh. This evidence is known as the
Dunn Inscription, which consists of the faintly etched words "Dunn 1869" on a boulder near the top of
Mt. Dellenbaugh. Some accounts also describe an arrow pointing towards water north of Mt.
Dellenbaugh (Belshaw 1979) but a recent October 2013 visit by a hiker suggests otherwise (Surgent
2013).
Using the known departure point of the Dunn – Howland party (Separation Canyon) and a known arrival
point at Mt. Dellenbaugh, this paper will attempt to answer the question concerning possible routes up out
of the Grand Canyon using Cost Distance and Least Cost Path analysis. Assuming that major landmarks
such as mountaintops would have influenced the group's choice of routes, this paper will also explore how
visible such major landmarks were along their chosen route using Visibility analysis.
Study Area
The study area encompasses a small section of the northern rim of the Grand Canyon in northwestern
Arizona, in an area known as the Arizona Strip. The specific area focused on in this paper runs from the
junction of Separation Canyon with the Colorado River on the south end to Mt. Dellenbaugh (located on
the top of the Shivwits Plateau) on the north end.

3. 2
Figure 1. Location of the study area within northwestern Arizona.
The portion of the Shivwits Plateau under analysis is a long and narrow peninsula roughly 19 miles in
length, and between 2 to 5 miles wide. This peninsula begins roughly 5 miles southeast of Mt.
Dellenbaugh and ends at Kelly Point on its south end; the south end overlooks the Colorado River. This
portion of the Shivwits Plateau ranges in elevation from 6,000 ft. on its southern end to around 6,300 ft.
near its northern terminus.
To provide a sense of the conditions that the Dunn – Howland party would have experienced the elevation
at the start of their journey is about 1,277 ft. while Mt. Dellenbaugh itself is at 7,072 ft. The terrain
within Separation Canyon is a wide gravelly wash enclosed by high granite walls with brushy vegetation,
especially near the water (Belshaw 1979). The vegetation becomes scrubbier as one approaches the upper
edge of the plateau – sheer rock walls and talus slopes are also the norm. Once one is on top of the
plateau the vegetation is a mix of Juniper – Piñon forest interspersed with desert scrub vegetation;
Ponderosa Pine stands become more common as one gains elevation towards the northern end of the
study area (Belshaw 1979, author's personal experience).

4. 3
Analysis Questions
This paper will address the following questions, using a GIS for the analysis:
1. What possible routes are there from Separation Canyon to Mt. Dellenbaugh?
2. Would some routes be more strenuous than others (measured by overall slope rise and distance)?
a. Are some routes better (or at least more likely) than others in terms of slope and
vegetation?
3. What landmarks are visible from the possible routes?
a. Where does Mt. Dellenbaugh become visible?
b. Are there other prominent landmarks along the possible routes?
To answer the first question the Cost Distance and Least Cost Path tools will be utilized. The Cost
Distance tool will give an estimate as to the travel costs across the landscape – in this case, the cost of
traversing steep slopes, certain types of vegetation, and crossing permanent water sources. Weighting
these variables will provide additional options to consider when attempting to model the most realistic
path the group may have taken to get to Mt. Dellenbaugh.
The biggest factor in determining how the group arrived at Mt. Dellenbaugh will be the slope grades that
they had to traverse; vegetation and water crossings are relatively minor considerations, especially given
that there are so few water crossings of any sort along the likeliest travel routes. To answer the second
question, the analysis will consider these factors in three ways: first by using the slope cost only, then the
slope and vegetation cost, and finally all three cost factors together (slope, vegetation, and water
crossings). The length of each of the resulting three least cost paths, as well as the overall elevation
gain/loss along each path, will be calculated and used to answer question 2a.
The third set of questions will be answered using Visibility analysis. It is assumed that the Dunn –
Howland group would have used major landmarks as a way to orient themselves through an unfamiliar
landscape on their trek north towards the Mormon settlements. To determine what was visible to them
(and where) a series of observation points will be created using the three least cost path outputs as a
guide. The observation point locations to be analyzed are as follows:
 The view from Separation Canyon
 The view from the plateau edge for each of the three least cost paths
 The view from Blue Mountain (as suggested by Belshaw (1979:114) during his recreation attempt
of the Dunn – Howland trip)
Informing the analysis discussion will be the results of Mike Belshaw's (1979) recreated trip up
Separation Canyon to Mount Dellenbaugh. Without using a map, Belshaw had hiked up using only the
landscape features as he had come across them as a guide for where to go up next. What he had
discovered was that there was only one likely way up Separation Canyon; this route takes one up the
eastern fork of Separation Canyon and ends near an area now known as Kelly Tanks. The route then
follows the Kelly Point peninsula north to Mount Dellenbaugh, stopping at Blue Mountain and Ambush
Water Pockets along the way (Belshaw 1979).

5. 4
Data Sources and Processing
All base data was obtained from the United States Geological Survey (USGS) National Map Viewer;
additional datasets were derived from these files. All base data was re-projected to NAD 1983 (2011)
State Plane Arizona West FIPS 0203 meters. A description of the base data used and processing
techniques applied are as follows:
DEM: Two DEM rasters were used in the analysis (USGS NED 1 arc-second 2013 1 x 1 degree images;
basic latitude/longitude identifiers are N36 W114 and N37 W114). To prepare these for use the raster
images had to be mosaicked and then clipped to the study area extent. The DEM mosaick was used to
obtain a slope raster (for analysis) and a hillshade raster (for report presentation purposes).
Arizona Place Names: This was a text file of all place names within the state of Arizona. The text file
contained geographic coordinates which were used to export the text file to a shapefile. Specific place
names (such as Mt. Dellenbaugh and Separation Canyon) were then exported to create a source and
destination shapefiles, respectively. This dataset was also used to create a shapefile of specific places
within the overall study area.
National Landcover Dataset: This is a GeoTIFF raster file (3 x 3 degree) and was used to obtain the
types of vegetation within the study area. The raster was clipped to the study area extent, then was
reclassified according to land cover type; the reclassified land cover raster is what was used for the
analysis.
National Hydrography Dataset: The dataset used specifically covers the Lower Colorado – Lake Mead
HU4 region. The NHDPoint and NHDLine shapefiles were clipped to the study area extent; the
NHDPoint shapefile was converted to a raster and reclassified based upon point type. Upon reviewing
the NHDLine and NHDWaterbody shapefile it was discovered that none were present between Separation
Canyon and Mt. Dellenbaugh and so were left out of the analysis; the NHDLine data was kept solely for
report presentation purposes.
Government Unit – United States: A shapefile of state boundaries was used for report presentation
purposes. This data was projected to the current project's coordinate system only – no further processing
was required for this dataset.

6. 5
Analysis
The following analysis steps were taken:
Notes on the Reclassify Tool Parameters
The slope raster was reclassified for the Cost Distance and Cost Path tools to reflect a graduated change in
difficulty as the degree of the slope increases.
Table 1. Slope Reclassification Values
Original Value (in Degrees) Reclassed Value
0 - 5 1
6 – 10 2
11 – 15 5
16 – 20 10
21 – 25 15
26 – 30 25
31 – 35 35
35 – 40 50
41 – 45 100
36 – 50 300
51 – 80 500
The vegetation data (derived from the land cover dataset) was reclassified to show minor increases in
travel cost depending on the vegetation. Admittedly the reclassification system used is subjective,
however there is a slight addition of difficulty when walking through areas characterized by thick scrubby
vegetation as opposed to bare earth or relatively open forest land.
Additional Path Distance Analysis
Ran tool with Modified Tobler's Hiker Function + 3 Cost Rasters Ran tool with Original Tobler's Hiker Function + 3 Cost Rasters
Viewshed Analysis
Ran on Separation Canyon & Blue Mountain
Ran on digitized plateau edge points determined from the Cost Path
results
Determined Optimal Paths
Ran Cost Distance Tool Using the Slope Cost only, Slope + Vegetation
Costs, and Slope+ Vegetation + Water Costs
Ran Cost Path Tool Using the Slope Cost only, Slope + Vegetation
Costs, and Slope+ Vegetation + Water Costs
Reclassified Data
Add Slope and Vegetation Rasters Add Slope, Vegetation, and Water Rasters

7. 6
Table 2. Vegetation Reclassification Values
Original Vegetation Value Reclassed Value
11 – Open Water 500
31 – Barren Land 1
42 – Evergreen Forest 3
52 – Shrub/Scrub 100
71 – Herbaceous 2
Upon reviewing the water data it became clear that only the NHDPoints shapefile would be required – no
significant water bodies or streams were present within area of interest. The NHDPoints shapefile was
converted to raster data in order to integrate seamlessly into the analysis. The NHDLines shapefile was
kept for report display purposes; to the end only named waterways were used in the report graphics.
Table 3. Water Reclassification Values
Original Water Value Reclass Value
458 – Spring or seep 100
487 – Waterfall 500
Notes on the Path Distance Tool
During the literature review for this project the use of Tobler's Hiker function was discovered as a way to
account for the costs associated with travelling on foot (Whitley & Hicks 2003). While the hiker function
is normally associated with assessing travel costs in terms of time and speed (Tobler 1993), it could be
applied to this project as well by using the Path Distance tool.
In the spirit of experimentation I had created two tables of slope values (in degrees) based on Tobler's
Hiker function and applied them as an additional cost along with all three cost parameters discussed
above (slope, vegetation, and water). The first table created uses a modified version of Tobler's formula
to account for off-path travel, and the second table created uses the original unmodified formula; results
from this have been designated as Path Distance 1 and Path Distance 2, respectively.
Table 4. Tobler's Hiker Function Formulas
Modified to show off-path travel 0.6*(6*EXP(-3.5*ABS(SLOPE+0.05)))
Original unmodified formula 6*EXP(-3.5*ABS(SLOPE+0.05))

8. 7
Results
Figure 2. Comparison of the Least Cost Path routes.
Least Cost Path 1 shows the results from using the slope as the only cost factor, and roughly follows the
route that Belshaw (1979) had traversed in his attempt to recreate the Dunn – Howland journey. Cost
Paths 2 and 3 are remarkably similar, but this isn't too surprising given that there was very little in the
way of water crossings that would have skewed the data. Of note is that all paths seem to cross over
Ambush Water Pocket – this area was identified by Belshaw (1979) as being one of the anecdotally
known locations for the murder (which is an unsubstantiated story by Frederick Dellenbaugh, a member
of the original Powell expedition party who had elected to stay on the river).

9. 8
Figure 3. Comparison of the Cost Paths and Path Distance derived routes.
Table 5. Total Length of All Potential Routes
Total Mileage
Cost Path 1 30
Cost Path 2 26
Cost Path 3 26
Path Distance 1 21
Path Distance 2 30
Figure 3 above shows the results of the Path Distance tool compared with the Least Cost Paths. What is
interesting is that the results from Path Distance 2 (showing use of the unmodified Tobler's Hiker
Function along with all three travel costs) almost exactly resembles the route of Cost Path 1 (which used
slope as its only travel cost).
The modified version of the Tobler's Hiker Function, shown as Path Distance 1, seems to be completely
inaccurate and is not being seriously regarded as a possible route. The terrain that it covers includes some
exceptionally steep elevation gains and losses – despite its relatively short distance in terms of mileage
(which would not have been known to the members of the Dunn – Howland party anyway) it would have
presented an extreme physical challenge and would have been eschewed in favor of obviously easier
routes north.

10. 9
Figure 4. Comparison of the Viewshed Analysis data.
Figure 5. Comparison of the Viewshed Analysis data in relation to the Cost Paths.

11. 10
The views from Separation Canyon are quite minimal – as to be expected from the bottom of a steep
canyon. It would appear that the Dunn – Howland party had taken their journey up the canyon on a bit of
faith. The view shed from the edge of the plateau along Cost Path 1 is promising – while not shown very
clearly in Figures 4 and 5 above the view does include a small portion of the southern extent of Blue
Mountain. The view shed from Blue Mountain does include Mount Dellenbaugh – this follows the
expected series of views, as outlined by Belshaw (1979).
Interpretation of Results
Figure 6. Comparison view showing the results of the Cost Path, Path Distance, and Viewshed tools.
In sum, it appears that Cost Path 1 and Path Distance 2 are the most likely routes. Both tend to generally
follow the route as experienced by Belshaw (1979), and views present along both routes would have most
likely influenced the next steps for the Dunn – Howland party. These routes are also the most believable
in terms of traversing the slope; aside from the initial push up the side of the plateau as one gains the top
it would have been physically less challenging. Dunn and the Howland brothers would not have had any
way of knowing this, however – they would have only been able to choose the route up that seemed most
physically possible.
Paths 2 and 3 are also likely route candidates, although Belshaw (1979) had explored the side canyons
along Separation Canyon in an attempt to find a way out and had noted that his route was the only one

12. 11
that seemed physically possible. It is assumed that the Dunn – Howland party would have explored the
side canyons in a similar manner and thus would have come to the same conclusion. Furthermore,
assuming that landmark views would have helped propel the Dunn – Howland party forward there is a
remarkable lack of any along the edge of the plateau at the location of Cost Paths 2 and 3.
Path Distance 1 is unlikely given its extreme elevation gain and loss. The Dunn – Howland party would
have been more likely to follow the easier options as presented by Cost Paths 1 – 3. Path Distance 2
appears to mimic the results obtained from Cost Path 1 – it is unclear if this bolsters the likelihood of Cost
Path 1 as being the route Dunn and the Howland brothers used or if it is simply an anomaly.
It is important to note that these findings are only a model – and the use of Tobler's Hiker Function is a
very good reminder of this. It seems that the use of Tobler's Hiker Function was an unhelpful addition to
the analysis. This is especially true given that its primary purpose is to determine how long it would take
a hiker to traverse an area – not how much effort a hiker would need to put in to walk an area.

13. 12
Conclusions
In conclusion, it does appear that Belshaw (1979) may have been 'on the right path' with his walking
study, as his route nearly follows the results of Cost Path 1. Slope most likely was the determining factor
for the Dunn – Howland party, especially given the landscape extremes they were presented with. The
results of the viewshed analysis at the plateau edge of Cost Path 1 are intriguing, as it leads to Blue
Mountain – and the views from Blue Mountain lead to Mount Dellenbaugh. For a group of men who had
never before been in that area, this would have been an important consideration for determining how to go
north towards the Mormon settlements.
Some ideas for future work include field testing the visibility analysis results and adding additional cost
parameters to the analysis. The Path Distance tool on the whole does seem to be the better choice for
analysis, however determining an appropriate method to model walking travel costs will take a bit more
research. Other parameters may be useful as well, such as soil types or the presence/absence of large
boulder fields and talus slopes. The existing parameters (vegetation cover and water) could also be
tweaked to display historic conditions – for example, historic rainfall averages could be extrapolated for
1869 and applied in some way to model the presence or absence of water in the ephemeral drainages and
known water pockets. Field testing Cost Paths 2 and 3 could also prove useful to finally determine if
alternate ways up were in fact possible.

14. 13
References Cited
Belshaw, M. (1979) The Dunn-Howland Killings: a Reconstruction. The Journal of Arizona History,
20(4), 409-422.
Compton, T. (2013) A Frontier Life: Jacob Hamblin, Explorer and Indian Missionary. Salt Lake City,
University of Utah Press.
Dobyns, H. F. & Euler, R. C. (1980) The Dunn-Howland Killings: Additional Insights. The Journal of
Arizona History, 21(1), 87-95.
Stegner, W. (1953) Beyond the Hundredth Meridian: John Wesley Powell and the Second Opening of
the West. New York, New York: Penguin Books.
Surgent (2013, October 16) Mount Dellenbaugh on SummitPost.org. Retrieved from
http://www.summitpost.org/mount-dellenbaugh/872332.
Tobler, W. (1993) Non-isotropic Geographic Modeling. Technical Report 93-1, Santa Barbara, CA:
National Center for Geographic Information and Analysis.
Whitley, T. G. & Hicks, L. M. (2003) A Geographic Information Systems Approach to Understanding
Potential Prehistoric and Historic Travel Corridors. Southeastern Archaeology, 22(1), 77-91.