new lab 1 gis for hydrology and water quality preparation · 2013. 3. 19. · lab 1 – gis for...

GIS in APES – Spring 2012 Eric Anderson

Mr. Johnston, Bob Jones High School [email protected]

Ms. Adkison, James Clemens High Schools 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 . If a “Getting started” window opens, select “Blank Map” and hit

OK.

2. First, we’ll add a Basemap and cover some basic navigation. Click the down arrow next to the

Add Data button.

http://nsstc.uah.edu/~anderse/gisinapes.html

Lab 1 – GIS for hydrology and water quality Eric Anderson, UAHuntsville

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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 button, click and drag to the new location you’d like

to have centered in your window.

4. To zoom, you can either use the mouse’s scroll wheel or magnifying glass icons near the

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 allow you to do a fixed zoom in, while


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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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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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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. Be sure to select the area button and

choose Area / Kilometers for proper units.

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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16. Now hit the ArcToolbox Window button , and drag the window that pops up to the right of

your map document to dock it in place.

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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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 / Flow Direction. Use

dem as the input, and name the output fdir. Hit Ok.

.

What do the eight values of the resulting fdir (flow direction) represent?

_______________________________________________________________

21. Next, open Spatial Analyst Tools / Hydrology / Flow Accumulation. This time, use fdir

as the input, and name the output facc. Hit Ok.

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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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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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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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 Spatial Analyst Tools / Hydrology /


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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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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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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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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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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? ________________

http://maps.huntsvilleal.gov/public/

new lab 1 gis for hydrology and water quality preparation · 2013. 3. 19. · lab 1 – gis for...

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