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George Mason University Department of Civil, Environmental and Infrastructure Engineering
Dr. Celso Ferreira
Prepared by Lora Baumgartner December 2015 Revised by Brian Ross July 2016
Exercise Topic: GIS and Water Resources Engineering (ArcGIS Spatial Analyst)
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Objective: Delineate GMU Watershed using ArcGIS Spatial Analyst-Hydrology Tools
Challenges:
a) Set up a model builder model to automate your analyses
b) Compare and contrast the results from the three resolutions (1 arc-second, 1/3 arc-second, 1/9 arc-second) in terms of computational
time and precision
c) Compare and contrast the results from multiple Stream Network thresholds (500, 1000, 5000, 10000).
**Refer to the ArcGIS Resource Center for definitions and context of the steps and tools in this tutorial, currently found at
http://resources.arcgis.com/en/help/main/10.1/index.html#//00qn0000013t000000**
Tutorial DEM obtained from GMU Campus Lidar file (provided)
Versions used for this tutorial: ArcMap 10.2.2 (Student), ArcCatalog 10.2.2
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Part 1: Prepare Project
Prepare Arc Catalog
1. Open ArcCatalog. Click the icon labeled “Connect To Folder”.
2. Select the preferred file folder location for ArcGIS project components. The default Geodatabase location is not recommended. The campus DEM file and all project data should be saved to a separate file location.
3. Click “Okay”.
4. Note that ArcCatalog is now showing the GMU Campus DEM file. The associated folder must be selected in the Catalog Tree window. Press F5 throughout the project to refresh ArcCatalog.
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5. Under the File Menu, hover over
the New drop-down menu.
6. Select “File Database”.
7. Specify the preferred name for the new File Database. The File Database (“GDB”) will hold ArcMap components.
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Create New Project
1. Open ArcMap. Select “Blank Map” from the New Maps menu.
2. Set the Default Geodatabase as the newly-created GDB from the previous section of this tutorial.
3. Click “OK”.
4. Select “Extensions” from the Customize menu on the top toolbar.
5. Enable (checkmark) all extensions.
6. Click “Close”. Extensions enable specific analytical functionality within ArcMap.
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7. Select “ArcToolbox” from the
Geoprocessing menu on the top toolbar.
8. Note the ArcToolbox menu in the right sidebar. This tutorial will focus on Spatial Analyst Tools > Hydrology.
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Create Project
1. Select “Save As” from the File menu on the top toolbar.
2. Select the preferred file folder location.
3. Specify the preferred project name.
4. Click “Save”.
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Add Data
1. Select “Add Data” from the File menu.
2. Locate the file location of the previously-downloaded GMU Campus DEM.
3. Select the GMU Campus DEM file.
4. Click “Add”.
5. Note that a DEM Layer has been added in the Table of Contents window on the left sidebar.
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6. Select “Add Basemap” from File >
Add Data.
7. Select the preferred map. “Topographic” is recommended for this tutorial.
8. Click “Add”.
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9. Note that a Basemap Layer has
been added in the Table of Contents window on the left sidebar.
The basemap provides helpful visual context for the DEM. However, graphical rendering of the basemap can slow computations and rendering of later graphics. Any layer can be hidden by unchecking the box next to the layer title. Any layer can be removed from the ArcMap project by right-clicking on the Layer name. Removing a layer in ArcMap does not delete the layer from the project. The layer is still filed with the project in ArcCatalog.
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Part 2: Terrain Preprocessing
Fill Sinks
1. Double-click “Fill” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Surface Raster field.
3. Locate the file folder containing the GMU Campus DEM.
4. Select the GMU Campus DEM file.
5. Click “Add”.
6. Click “Okay” to create the Fill Sinks layer.
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7. Note that a Filled-DEM Layer has
been added in the Table of Contents window on the left sidebar.
No change will be rendered to the DEM graphic.
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Flow Direction
1. Double-click “Flow Direction” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Surface Raster field.
3. Navigate to the project file database that was created earlier in this tutorial.
4. Select the Filled-DEM file.
5. Click “Add”.
6. Click “Okay” to create the Flow Direction layer.
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7. Note that a Flow Direction Layer
has been added in the Table of Contents window on the left sidebar.
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Flow Accumulation
1. Double-click “Flow Accumulation” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Flow Direction Raster field.
3. Navigate to the project file database that was created earlier in this tutorial.
4. Select the Flow Direction file.
5. Click “Add”.
6. Click “Okay” to create the Flow Accumulation layer.
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7. Note that a Flow Accumulation Layer has been added in the Table of Contents window on the left sidebar.
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Extract Stream Network
1. Double-click “Raster Calculator” from the ArcToolbox > Spatial Analyst > Map Algebra menu.
2. Click “Con” in the right window.
3. Click the Flow Accumulation Layer in the left window.
4. Add the threshold for stream delineation.
The recommended threshold for this tutorial is 50,000.
5. Click “Okay” to create the Stream
Extraction (Raster Calculator) Layer.
6. To improve the visual representation of the Stream Network, right-click on the Stream Extraction (Raster Calculator) Layer.
7. Select “Properties”.
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8. Select the tab labeled “Display”.
9. Select “Majority (for discrete
data)” from the Resample drop-down menu.
10. Select the tab labeled “Symbology”.
11. Right-click the Color Block to the left of the “1”.
12. Select the preferred color for Streams.
13. Click “Okay”.
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14. To show the stream network,
enable the Basemap and Raster Calculator layers and disable all other layers.
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Stream Link
1. Double-click “Stream Link” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Stream Raster field.
3. Navigate to the project file database that was created earlier in this tutorial.
4. Select the Raster Calculator (Stream Network) file.
5. Click “Add”.
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6. Click on the file folder icon to the
right of the Input Flow Direction Raster field.
7. Navigate to the project file database that was created earlier in this tutorial.
8. Select the Flow Direction file.
9. Click “Add”.
10. Click “Okay” to create the Stream Link layer.
11. Repeat steps 6 through 9 of the previous task (“Extract Stream Network”) to improve the visual representation of the stream links.
12.
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13. Note that a Stream Link Layer has
been added in the Table of Contents window on the left sidebar.
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Stream Order
1. Double-click “Stream Order” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Stream Raster field.
3. Navigate to the project file database that was created earlier in this tutorial.
4. Select the Raster Calculator (Stream Network) file.
5. Click “Add”.
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6. Click on the file folder icon to the
right of the Input Flow Direction Raster field.
7. Navigate to the project file database that was created earlier in this tutorial.
8. Select the Flow Direction file.
9. Click “Add”.
10. Click “Okay” to create the Stream Order layer.
11. Repeat steps 6 through 13 of the previous task (“Extract Stream Network”) to improve the visual representation of the stream links.
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12. Note that a Stream Link Layer has
been added in the Table of Contents window on the left sidebar.
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Stream to Feature
1. Double-click “Stream to Feature” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Stream Raster field.
3. Navigate to the project file database that was created earlier in this tutorial.
4. Select the Raster Calculator (Stream Network) file.
5. Click “Add”.
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6. Click on the file folder icon to the
right of the Input Flow Direction Raster field.
7. Navigate to the project file database that was created earlier in this tutorial.
8. Select the Flow Direction file.
9. Click “Add”.
10. Click “Okay” to create the Stream Order layer.
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11. Note that a Stream Link Layer has
been added in the Table of Contents window on the left sidebar.
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Flow Length
1. Double-click “Flow Length” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Flow Direction Raster field.
3. Navigate to the project file database that was created earlier in this tutorial.
4. Select the Flow Direction file.
5. Click “Add”.
6. Click “Okay” to create the Flow Accumulation layer.
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7. Note that a Flow Length Layer has
been added in the Table of Contents window on the left sidebar.
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Identify Basins
1. Double-click “Basin” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Flow Direction Raster field.
3. Navigate to the project file database that was created earlier in this tutorial.
4. Select the Flow Direction file.
5. Click “Add”.
6. Click “Okay” to create the Flow Accumulation layer.
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7. Right-click on the new Basin Layer
and select Properties.
8. Select the tab labeled “Display”.
9. Set the transparency to 50%.
10. Click “Okay”.
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11. Note the new Basin Layer overlaid
on the Base Map.
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Create Watershed Outlet (Point Feature)
1. In ArcCatalog, select “Shapefile” from File > New.
2. Specify a name for the new outlet Point.
3. Confirm that the Feature Type is “Point” in the drop-down menu.
4. Click “Edit” to assign a coordinate system to the new Point.
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5. Click the plus sign next to “Projected Coordinate Systems”.
6. Click the plus sign next to “State Plane”.
7. Click the plus sign next to “NAD 1983 (US Feet)”.
8. Select “NAD 1983 StatePlane Virginia North FIPS (US Feed)”.
9. Click “Okay”.
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10. Click “Okay” on the Create New
Shapefile window.
11. In ArcMap, select “Add Data” from File > Add Data.
12. Select the new outlet Point.
13. Click “Okay”.
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14. Right-click the outlet Point and
select “Start Editing” from the Edit Features menu.
15. If a warning about spatial references is shown, check the box indicating that work can continue.
16. Click “Continue”.
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17. Zoom in on the Braddock Road
outlet point on the map, as shown to the right.
A scale of approximately 1:35 is recommended for this step to ensure optimal accuracy.
18. Click the Point in the “Create Features” work menu at the right of the screen.
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19. Place the outlet Point at the
campus outlet, as shown to the right.
20. Click “Stop Editing” from the Editor Toolbar.
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Identify Watershed
1. Double-click “Watershed” from the ArcToolbox > Spatial Analyst > Hydrology menu.
2. Click on the file folder icon to the right of the Input Flow Direction Raster field.
3. Navigate to the project file database that was created earlier in this tutorial.
4. Select the Flow Direction file.
5. Click “Add”.
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6. Click on the file folder icon to the
right of the Input Flow Direction Raster field.
7. Navigate to the project file database that was created earlier in this tutorial.
8. Select the Flow Direction file.
9. Click “Add”.
10. Click “Okay” to create the Stream Order layer.
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11. Note that the new Watershed
Layer has been created.
If watershed is not visible, the Outlet (Point) may not be placed accurately. Enable the Stream Link Layer and zoom in to approximately 1:35 scale on the Point. If the Point Feature is not placed directly in the stream line, repeat steps 14 through 20 in the “Create Watershed Outlet” task. Repeat the Create Watershed task (this section).
