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Maggie Hutson 12‐01‐2011 GIS & GPS GEO 327G
Project Report
I. Introduction
Endangered species are protected under the Endangered Species Act and regulated by
the U.S. Fish and Wildlife Service. Areas where these species are found have more
developmental and environmental regulations, and so in a way inhibit “economic progress”. It is
of utmost importance to establish areas where it is likely that these species occur so that
developers can plan accordingly. George Veni established zones of varying likelihood where
endangered karst invertebrates might occur in Travis, Williamson, and Bexar counties based
upon the location of the Edwards Formation, both laterally and vertically.
II. Problem formulation
My first idea for this project was to incorporate slope, elevation and the location of the
Edwards Formation to calculate my own version of the Veni lines to compare them to the lines
that George Veni has created to predict where caves with potential endangered karst
invertebrates might live. I also wished to compare my own “Veni lines” to known locations of
caves with endangered karst vertebrates. The location of these caves is kept highly secret, so
unfortunately was unable to do this. Therefore, my final product took into account the Edwards
Formation outcrop as well as the slope. Contour lines are also present on the map to give an
idea of elevation.
III. Data Collection
Since Bexar County does not adjoin Travis and Williamson Counties the data for this
project oftentimes repeats itself since I had to get it separately for these counties. I got the
Bexar Count Karst Zone Shapefile as well as the Travis and Williamson County Karst Zone
Shapefile off of the U.S. Fish and Wildlife Service’s Austin Ecological Services Office’s website
located at http://www.fws.gov/southwest/es/austintexas/Maps_Data.html. I received the
Edward Limestone Outcrop Shapefile from Dr. Helper. He took the shapefile from the Geologic
Map of Texas, extracting any polygons that were classified as some kind of Edwards Formation.
I downloaded two DEMs off of the Seamless Server located at
http://seamless.usgs.gov/website/seamless/viewer.htm. Due to the size of the area I had to
download a DEM for Travis and Williamson Counties, and a second one for Bexar County. This
allowed me to only download two sets of DEMs instead of the four it would have taken me
otherwise. I also poached the Texas counties shapefile from lab 2. This lab had a map of Texas
with all of the 254 counties.
IV. Data Preprocessing
Bexar County Karst Zone Shapefile and Travis & Williamson County Karst Zone Shapefile
were downloaded as zip files, so had to be unzipped. The Edward Limestone Outcrop Shapefile
was also downloaded as a zipped file off of an online site Dr. Helper sent to me; this also had to
be unzipped before use. The two DEMs did not come with spatial referencing, so I had to go to
the Seamless Server and figure out what spatial reference system they were in. I then had to
access the files in ArcCatalog. Under properties I had to assign the two DEMs with the
Geographic NAD 83 spatial reference system that they were given in. The three counties I was
interested in had to be extracted from the Texas counties shapefile. I had to select Williamson
and Travis county and extract the data to their own shapefile, then I had to repeat this for Bexar
County.
V. ArcGIS Processing
Once the data preprocessing was complete and all other data was downloaded I started
to “clean up” the data so that it would be in the form that I would want it for my project. This
first entailed projecting the DEM raster into the Projected NAD83 spatial reference system for
both the Travis/Williamson County DEM and the Bexar County DEM. After this was completed I
then had to clip both of these DEMs to their respective counties so that the elevation data only
shows up in the area I am interested in. I then had to clip the Edwards outcrop shapefile first to
the Travis/Williamson County shapefile, then perform a second clip to clip it to the Bexar County
shapefile. I had to clip the Travis and Williamson County Karst Zone Shapefile to within the
bounds of Travis and Williamson County. Then I clipped the Bexar County Karst Zone shapefile
so that it only showed up in Bexar County. I then created contours for Travis/Williamson County
and also for Bexar County; I created contours starting at 100 meters in 50 meter intervals the
last contour was at 450 meters in Travis/Williamson Counties and 600 meters in Bexar County
(Figure 1).
Figure 1. Fifty meter Contour Map of Williamson and Travis Counties
Then I had to do slope calculations for each of the raster datasets. I first did the slope calculation with
no z factor, however this turned up a slope raster for Travis and Williamson County that was obviously
wrong (Figure 2).
Figure 2. An incorrect way to create a slope raster for Travis and Williamson Counties
This made me realize that the horizontal spatial reference system was actually in decimal degrees, and
not in meters like the vertical spatial reference was. This meant that I had to go to Data Management
ToolsProjections and TransformationsRasterProject Raster. I put in the DEM as my input, saved it
to my geodatabase and gave the output an appropriate name. The Coordinate System I projected it into
was NAD_1983_StatePlane_Texas_Central_FIPS_4203, which would put the x and y lateral data into
meters like the elevation data was in. I then used the Spatial Analyst ToolsSurfaceSlope and
calculated the slope both for Travis/Williamson and Bexar Counties (Figure 3).
Figure 3. Slope Calculations for Travis and Williamson Counties
Now all of my generic calculations are out of the way, so I was able to start processing my data
in fuller depth. I opened the attribute table for each of the Edwards Formations and added a new field.
I entitled this field Rankings and gave every formation in the Edwards a ranking of 4. I am basing this off
of the assumption that anywhere the Edwards outcrops has the potential to contain caves, and
anywhere it does not outcrop, there are no caves. I then proceeded to Conversion ToolsTo
RasterPolygon to Raster. Under this tool put the input as the Edwards Formation, the output named
appropriately, the value field as your ranking field that I added. I left the cell assignment type as
cell_center. I changed the priority field to my ranking field NOTE: IMPORTANT this apparently makes
the difference in your raster being all one color versus it assigning many many different numbers to the
different vector polygons. The cell size I imported from the slope DEM, and under the environments
button the output extent I also put as the slope DEM’s coordinate system. The raster then comes out
like Figure 4 below.
Figure 4. Edwards formation as a raster, and slope for Travis and Williamson Counties
I then changed the slope symbology categories to 5 classes and based the ranges off of the
natural breaks. Thus I ended up with 5 different slope ranges 0‐2; 2‐5; 5‐10; 10‐15; 15‐53 for both
Travis/Williamson and Bexar Counties. I then reclassified each of these rasters based upon the different
slope categories giving them the values 4; 3; 2; 1; 0 respectively. I then added both of these rasters
under Spatial Analyst ToolsMap AlgebraRaster Calculator and they came out looking like Figure 5.
Figure 5. Raster of Slope Suitability and Location of Edwards Formation for
Travis and Williamson Counties
Due to the fact that my suitability model was already much more restricted than the model that
George Veni came up with, I decided not to further restrict my model by trying to factor in elevation as
another habitat suitability requirement.
VI. Conclusion
In comparing the two maps it is plain to see that the suitable habitat Veni Zones (Zones 1 and 2)
cover a much wider area than my entire suitable habitat zones. There could have been many
differences in the two calculations. Firstly, Veni could have used a geologic map that was made for a
smaller area instead of one for the entire state of Texas because oftentimes his zones appear to exceed
the Edwards Formation zone I have. Because these were thirty meter by thirty meter cells my slope
calculation covers a relatively expansive area and I could have eliminated some areas that actually are
suitable for habitat. I am also not entirely sure what Veni used to calculate these zones and I may have
left out a formation that is also suitable for caves, which could explain the slight disparity in our maps.
Unfortunately I am not able to compare my map to that of known cave locations with endangered
species because those locations are kept secure for various reasons. However, it is apparent that
suitable habitat probably exists throughout % of Travis and Williamson and % of Bexar Counties. So if
there are caves these endangered karst invertebrates could have a significant amount of suitable habitat
left, and hopefully they will endure.
Maggie Hutson12-2-11
FWS Veni Zones for Travis, Williamson and Bexar Counties
q0 20 4010 Miles
1:1,000,000
Zone 1 - Species Known to OccurZone 2 - Species Likely to OccurZone 3 - Species Probably do not occurZone 4 - Area which requires further rsearchEdwards Formation
Maggie Hutson12-2-11
Zones of Potential Caves with Karst InvertebratesIn Travis, Williamson, and Bexar Counties
50m contour linesNot likely habitatPossibly habitatProbably habitatLikely habitatVery likely habitatEdwards FormationCounty Boundaries
q0 2010Miles
1:800,000