GIS in APES – Spring 2012
Mr. Johnston, Bob Jones High School
Ms. Adkison, James Clemens High Schools
Eric Anderson
eric.anderson@nsstc.uah.edu
UAHuntsville ESS Program / ATS Department
Lab 1 – GIS for hydrology and water quality
Preparation
1. Open My Computer or Windows Explorer
2. Create a designated working directory (e.g., create a folder called GIS folder in C: drive)
3. Visit http://nsstc.uah.edu/~anderse/gisinapes.html, and navigate to “Lab 1 – GIS for hydrology
and water quality” to download datasets to C:\GIS (or your designated working directory)
4. Extract the downloaded file directly in C:\GIS (or your designated working directory)
ArcMap
1. Open ArcMap
OK.
. If a “Getting started” window opens, select “Blank Map” and hit
2. First, we’ll add a Basemap and cover some basic navigation. Click the down arrow next to the
Add Data button.
Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
The first time you load GIS data into ArcMap, you need to connect to a folder with your datasets.
Click the Connect to Folder button, and navigate to C:/GIS (or whatever the name of your
working directory is).
Once you have connected to your folder, select the raster dataset called “dem.” This is a Digital
Elevation Model, the basis for many types of hydrological and ecological modeling. Your map
document should look like this:
3. To pan around the map, select the hand
to have centered in your window.
button, click and drag to the new location you’d like
4. To zoom, you can either use the mouse’s scroll wheel or magnifying glass icons
hand. If you ever get lost, hit the globe button
to reset the zoom to the full extent of your
datasets. The four diagonal arrows pointing inward
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near the
allow you to do a fixed zoom in, while
Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
the four diagonal arrows pointing outward
allow you to do a fixed zoom out. You can also
use the blue left and right arrows to go back and forth between recent views.
5. What is the resolution of this DEM? _________________________ (include units)
a. Hint: right click on dem in the Table of Contents, select Properties, and choose the
Source tab.
6. What is the minimum elevation in this dataset? __________________________ (include units)
a. Does this minimum value make sense?
7. What is the maximum elevation in this dataset? ___________________________ (include units)
a. Does this maximum value make sense?
8. Save this map document. Call it Lab1_<your_name>, and be sure to save it in your GIS working
directory.
9. Apply a more interesting color scheme to the DEM by opening up its symbology. Still in the
Layer Properties window, select the Symbology tab. Choose a color ramp suitable for elevation,
by Stretch type select Percent Clip, and under Statistics choose “From Current Display Extent.”
Hit Ok.
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
10. Using the zooming and panning tools, try finding the highest elevation. To query or identify the
value at a specific point, use the Identify button.
11. What state has the highest elevations? To see state and county boundaries hit Add Data
again, and select AL_counties.shp and US_states_conus.shp (hold Ctrl while clicking to
select both). Hit Add.
12. Now we can’t see the DEM beneath the states and counties. Start by changing the symbology of
the states layer. Right click on US_states_conus and select Properties. Choose the Symbology
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
tab, and click the large rectangle below the word “Symbol.” Choose the Hollow symbol to only
show outlines. You can opt to change the outline color here. Hit OK twice to return to the map.
Between which two states is the highest point in this DEM? _____________________________
13. Change the symbology for the Alabama counties layer so that it is also hollow. You may decide
to pick a different outline color or thickness.
14. Use the Measure tool to estimate the area of Alabama.
choose Area / Kilometers for proper units.
Be sure to select the area button and
Click to draw a polygon around the state. Double click to close the polygon, and look at your
Measure window. How many square kilometers did you meausre? ______________________
15. To further enhance our topographic view, we will begin to use Geoprocessing tools. To access
the required extensions, click the Customize menu and select Extensions… Be sure that 3D
Analyst and Spatial Analyst are selected. Leave the rest as they are.
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Lab 1 – GIS for hydrology and water quality
16. Now hit the ArcToolbox Window button
your map document to dock it in place.
Eric Anderson, UAHuntsville
, and drag the window that pops up to the right of
17. Open
Spatial Analyst Tools / Surface / Hillshade.
18. Fill in the tool using the figure below as a guide. The input raster should be the dem in your
Table of Contents. Name the output raster hillshade and be sure to put it in the same folder!
Keep the rest of the fields with their default values. Hit Ok and wait for the process to run.
19. Double click on hillshade in the table of contents to open the properties. On the Display tab,
change the transparency to 80%.
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
20. We will now use this DEM to locate rivers and outline watersheds (a.k.a. areas of influence). In
the ArcToolbox Window, open
Spatial Analyst Tools / Hydrology /
dem as the input, and name the output fdir. Hit Ok.
Flow Direction. Use
.
What do the eight values of the resulting fdir (flow direction) represent?
_______________________________________________________________
21. Next, open
Spatial Analyst Tools / Hydrology /
as the input, and name the output facc. Hit Ok.
Flow Accumulation. This time, use fdir
Where are the lowest values of facc, and what do they mean? Where are the highest values, and
what do they represent?
_______________________________________________________________
_______________________________________________________________
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
22. Now we will use a conditional statement tool to separate what we would like to define as rivers or
streams from the rest. Open
Spatial Analyst Tools / Conditional / Con. Select facc as the
input conditional raster, Expression: value > 100; Input true: 1; Input false: 0; Output raster str:
23. What do you notice about the values of the streams? ______________________________
24. To classify each stream segment with a unique ID, open
Spatial Analyst Tools / Hydrology /
Stream Link. Use str as the input, define the proper flow direction, and name the output
streams.
25. What do you notice about the values of these streams? _____________________________
26. Next, assign an order to each of the streams. This is a useful classifier for hydrology and water
resources. Open
Spatial Analyst Tools / Hydrology / Stream Order. Use streams as the
input, define the proper flow direction, and name the output str_order.
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
What do you notice about the values of these streams? _____________________________
27. Finally, convert these streams to a more useful data type (vector). Open
Spatial Analyst
Tools / Hydrology / Stream to Feature. Use str_order as the input, define the proper flow
direction, and name the output streams.
28. To apply a symbology based on the order, open the streams Symbology from the Table of
Contents (double click, or right click / Properties / Symbology tab). On the left, choose
Quantities / Graduated symbols. Under Value, choose GRID_CODE. Change the color to blue
by clicking on the box under Template. Change the number of classes to six.
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
What is the order of the Tennessee R. as it passes through northern Alabama? _____________
29. Now that we have used elevation to understand how surface runoff accumulates to form rivers,
we will delineate drainage watersheds. Open
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Spatial Analyst Tools / Hydrology /
Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
Watershed. Define the proper flow direction, use streams as the input pour point features, and
name the output wshed.
30. Apply a Symbology to show “Unique Values” to see how watersheds were traced around the
areas of influence for each river segment and tributary.
31. Now we will calculate the slope of the terrain. Open
Spatial Analyst Tools / Surface /
Slope. Use dem as the input, and name the product slope.
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
What is the maximum slope found from this analysis? ______________________ (include units)
32. Which parts of the streams we identified today might be most susceptible to soil erosion due to
steep slopes? We can calculate zonal statistics of the slope within each watershed. . Open
Spatial Analyst Tools / Zonal / Zonal Statistics. Use wshed as the input raster zone data. The
input value raster is our slope. Name the output slope_ws, and let’s calculate the MEAN slope
within each watershed.
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
Describe some of the uncertainties and limitations of this quick erosion susceptibility assessment.
_____________________________________________________________________________
_____________________________________________________________________________
33. Add the two population datasets, urban_areas_seus and pop_places_seus.
In what kind of terrain are the majority of the urban areas located? _______________________
Why might that be? ____________________________________________________________
Which populated places are situated among the steepest terrain? _________________________
34. Compare the locations of urban areas to rivers. Count the number of urban areas that have rivers
running through them. Instead of manually counting, use the Select by Location option. In the
Selection menu, choose Select by Location… and set urban_areas_seus as the target layer and
streams as the source layer:
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
35. You should see a number of urban highlighted in light blue. Right click on urban_areas_seus in
the Table of Contents and select Open Attribute Table…
Out of how many urban area polygons, how many were selected? _______ out of _______
36. Repeat the Select by Location process, but this time, set a search distance of 10 km.
How many were selected this time? ________________
How do you interpret this?
_____________________________________________________________________________
_____________________________________________________________________________
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Lab 1 – GIS for hydrology and water quality
Eric Anderson, UAHuntsville
Understanding topography also helps us to understand floods. Visit the city of Huntsville’s GIS online
maps (http://maps.huntsvilleal.gov/public/) to view floodways and flood fringe, which are important for
insurance rates.
 What are some areas within Madison and Limestone county that are more exposed to floods?
What do you find in these places? Urban development? Agriculture? Schools? Forests?
Wetlands?
______________________________________________________________________
______________________________________________________________________
Hint: Use the other layers found in the interactive map to better answer this.
 How far away is your school campus from a floodway? Flood fringe? ________________
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