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Table of Contents

In this lab, you will be learning a variety of geoprocessing tools, with a focus on those within the Hydrology toolset. You will start by learning how to recondition a DEM file. You will then calculate flow direction and flow accumulation and learn how to generate drainage lines and catchment basins. Be sure to save your progress often. 

Part 1:

Setting Up a

Continuing an Existing GIS Project

Opening an existing project

  1. Using Windows, navigate to your HydrologyLab folder from Labs 1 and 2.
  2. Double-click the HydrologyLab.aprx ArcGIS Project File.

Creating a new map

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Now you will create You will begin by creating a new map document for your project. You will begin by opening ArcGIS Profor Lab 3.

  1. Open the HydrologyLab.aprx file.
  2. On the Standard On the Standard toolbar, click the  the Insert tab and  tab and click New Map.
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  3. Double-click the Map title in the table of contents.

  5. Type Lab3 for Name. Click OK.At the top of the Contents pane, rename the map to "Lab3".

Adding data in ArcMap

You will begin by adding the data you previously copied into your geodatabase to the map.

  1. On In the catalog Catalog pane, expand the Databases section and Hydrologylabthe HydrologyLab.gdb file.Double-click the HydrologyLab geodatabase to expand it geodatabase.

Remember that the data frame map view takes on the projection of the first layer added to it. Because you spent time in Lab 2 to ensure that the the DEMft raster  raster was in the correct State Plane Texas South Central projection, you will add that layer first, so that your data frame map view will also display in the correct local projection.

  1. Drag the  the DEMft raster into the Map Display Lab3 map view.

You can now be sure that the data frame map view will display in the State Plane Texas South Central projection inherited from the the DEMft layer layer. Next you will add the the Flowlines layer layer.

  1. Click In the Catalog pane again and , drag the Flowlines and Subbasin feature class classes into the Map Display Lab3 map view.

Though the Flowlines feature class data is still stored in the NAD 1983 geographic coordinate system, in which it was originally provided from NHDPlus, the Flowlines layer is now being projected-on-the-fly into the State Plane Texas South Central projection of the data frame. Remember that projection-on-the-fly may suffice for the purposes of visual display only, but it cannot be used to calculate spatial relationships. Since you will be calculating many such spatial relationships throughout this lab, it is important for all data to be stored in same projection.

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You will now project the Flowlines layer into the State Plane Texas South Central projection.

  1. In the Analysis tab, click the Tools button to open the Geoprocessing pane.
  2. In the 'Find Tools' search box, type "project".
  3. Click the Project 
  4. Open Toobox.
  5. Double-click the Data Management Tools toolbox à Projections and Transformations toolset à Project tool.
  6. For ‘Input Dataset or Feature Class’, drag in the Flowlines layer from the Table of Contents.

Also notice that the output dataset defaults to your HydrologyLab geodatabase.

  1.  use the drop-down menu to select the Flowlines layer.
  2. For ‘Output Dataset or Feature Class’, rename “Flowlines “Flowlines_Project” Project” to “Flowlines“Flowelines_StatePlane”StatePlane”, since that is the name of the projection you will be using.
  3. For the ‘Output Coordinate System’ box, use the  use the drop-down menu to to select the DEMft layer.

Notice that the familiar State Plane Texas South Central projection is now listed. Because both the input and output coordinate systems are based on the NAD 1983 geographic coordinate system, no geographic transformation is required.

  1. Ensure your Geoprocessing pane Ensure your ‘Project’ window appears as shown below and and click Run Run.
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Now that you have a correctly projected layer, you no longer need the original NAD 1983 layer.

  1. In the Table of Contents pane, right-click the Flowlines layer and select Remove.
  2. Repeat the above steps 4-7 for the Subbasin layer to produce a Subbasin_StatePlane layer.
  3. Click Save on top of the menu bar to save the map documentSave your project.

Part 2: DEM Reconditioning

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First, you will convert the vector flowlines into a corresponding raster with exactly the same dimensions (rows, columns, cell size, and alignment) as the DEM raster. Every raster cell intersecting the flowlines will be assigned a value equal to the COMID (Common Identifier, or unique ID) of the intersecting vector flowline and all other raster cells will be assigned a value of NoData.

  1. At the top left of the Geoprocessing pane, click the Back button.
  2. In the search box, type "feature to raster".
  3. Click the Feature to Raster tool
  4. Click the Toolbox icon.
  5. Collapse the Data Management Tools toolbox.
  6. Double-click the Conversion Tools toolbox à To Raster toolset à Feature to Raster tool.
  7. For ‘Input features’, drag in the select the Flowlines_StatePlane layer from the Table of Contents.
  8. Use the ‘Field’ drop-down menu to For ‘Field’, select the COMID field.
  9. For ‘Output raster’, rename the raster from “Feature“Feature_Flow1” to “FlowlineRaster”Flow1” to “FlowlineRaster”.

In order to align the cells in this new flowlines raster with the cells in the DEM raster, you will alter the extent, snapping, and cell size using the Environments settings.

  1. At the top of the ‘Feature to Raster’ Geoprocessing window, click the Environments… button.
  2. For Extent, use the ‘Extent’ drop-down menu to select Same as layer DEMft.
    3. Use the ‘Snap Raster’ drop-down menu to select the DEMft raster.
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Notice that the output cell size has updated to 300. This is because you selected DEMft as the snap raster, which also has a cell size of 300.

  1.  click the Environments tab on the right.
  2. Under the 'Processing Extent' section, for 'Extent', select Same As layer: DEMft.

The listed Extent coordinates will be updated based on the geographic extent of the DEMft raster.

  1. Under the 'Raster Analysis' section, for ‘Cell Size’, select the Same as layer DEMft.
  2. For ‘Snap Raster’, select the DEMft raster.

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  3. At the top of the Geoprocessing window, click the Parameters tab on the left.
  4. Ensure your Geoprocessing pane Ensure your ‘Feature to Raster’ window appears as shown below and click Run.
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  2. In the Contents pane, uncheck the Subbasin_StatePlane layer.

If you zoom in closely, you will notice the raster cells intersecting the Flowlines_StatePlane layer have been added to the FlowlineRaster layer and are assigned a color.

 

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  1. Symbolize the FlowlineRaster layer using Unique Values based on the COMID values stored in the Value field, so you can see how the COMID values have been assigned to the cells.

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  2. In the Table of Contents pane, collapse the FlowlineRaster symbology.

Creating a binary raster

You currently have a raster where each cell contains either the COMID value or the value NoData. ( NoData cells are transparent, hence you can still see the DEMft layer beneath them. ) Ideally, you would like a raster where all the flowline cells are assigned a value of 1 to use as a simple flag.

  1. Click the ArcToolbox tab.
  2. Collapse the Conversion Tools toolbox.
  3. Double-click the Spatial Analyst Tools toolbox à Math toolset à Logical toolset à Greater Than tool.

Remember that utilizing any tools in the Spatial Analyst Tools toolbox requires first activating the Spatial Analyst extension, which you have already done.

  1. Return to the Geoprocessing pane.
  2. At the top left of the Geoprocessing pane, click the Back button.
  3. In the search box, type "greater".
  4. Click the Greater Than (Spatial Analyst Tools) tool.

The Greater Than tool creates a binary raster The Greater Than tool creates a binary raster with a value of 1 anytime the value in the first input raster is greater than the corresponding value in the second input raster. In this case, you would like to assign a value of 1 anytime the COMID value is greater than 1.

  1. For ‘Input raster or constant value 1’, drag in the select the FlowlineRaster layer from the Table of Contents.
  2. For ‘Input raster or constant value 2’, type “1” “1”.
  3. For ‘Output raster’, rename the raster from “Greater“Greater_Flow1” to “FlowlineBinary”Flow1” to “FlowlineBinary”.
  4. Ensure your ‘Greater Than’ window Geoprocessing pane appears as shown below and click Run.
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The resulting raster assigns each cell a value of 1 when it intersects with a flowline and a value of NoData when it does not intersect a flowline.

 

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Reclassifying a raster

Though you now have a uniform value of 1 to flag the presence of a flowline cell, the remaining cells have a value of NoData, which is not useful for performing mathematical operations across all the cells, so you would like to reassign all cells with a value of NoData to a value of 0.

  1. At the top left of the Geoprocessing pane, click the Back button.
  2. In the search box, type "reclassify".
  3. Click the Reclassify (Spatial Analyst)
  4. Click the Tools icon.
  5. Within the Spatial Analyst Tools toolbox, collapse the Math toolset.
  6. Within the Spatial Analyst Tools toolbox, double-click the Reclass toolset à Reclassify tool.
  7. For ‘Input raster’, drag in the select the FlowlineBinary layer from the Table of Contents.
  8. Use the For ‘Reclass field’ drop-down menu to , select the Value field.

In the ‘Reclassification’ table, you will see a list of old values and new values. You would like to maintain all old values of 1, but you would like to assign all old values of NoData NODATA to a new value of 0.

  1. In the New values column, replace the “NoData” “NODATA” value with a value of “0”“0”.
  2. For ‘Output raster’, rename the raster from “Reclass“Reclass_Flow1” to “Reclassify”.
  3. Click the Environments… button.
  4. For Processing Extent, use the ‘Extent’ drop-down menu to select Same as layer DEMft.
  5. Use the ‘Snap Raster’ drop-down menu to select the DEMft raster.
  6. Flow1” to “Reclassify”.
  7. At the top of the Geoprocessing window, click the Environments tab on the right.
  8. Under the 'Processing Extent' section, for 'Extent', select Same As layer: DEMft.
  9. Under the 'Raster Analysis' section, for ‘Cell Size’, select Same as layer DEMft.
  10. For ‘Snap Raster’, select the DEMft raster.
  11. At the top of the Geoprocessing window, click the Parameters tab on the left.
  12. Ensure your Geoprocessing pane Ensure your ‘Reclassify’ window appears as shown below and click Run.
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You will notice that the output raster is a rectangle that contains encompasses the geometry of the subbasin – , but does not match it exactly.  follow its curved boundaries. In the next section (, 'Calculating Euclidean Distances) distances', you will assign specify a “mask” that will define a more clip the output raster to the specific geometry .  The of the subbasin. In this case, the null values in this raster prevent this the input raster prevented a mask from being an option - , so we you will retroactively clip the reclassified raster.

  1. At the top left of the Geoprocessing pane, click the Back button.
  2. In the search box, type "clip".
  3. Click the Clip Raster tool
  4. Click the Toolbox icon.
  5. Double-click the Data Management toolbox àRaster toolset à Raster Processing toolset à Clip tool.
  6. For ‘Input Raster’, drag in select the Reclassify layer.
  7. Use the For ‘Output Extent’ drop-down menu to , select the Subbasin_StatePlane layer.
  8. Click ‘Use Use Input Features for Clipping Geometry’Geometry.

If this box was not checked, the output would be limited to the rectangular extent encompassing the subbasin, which is the same extent you already have.

  1. For ‘Output raster’, rename the raster to “FlowlineReclass”from Reclassify_Clip to “FlowlineReclass”.
  2. Ensure that your ‘Clip’ window your Geoprocessing pane appears as shown below and click Run.
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Notice that the extent of the output file is now in the shape of the subbasin.

  1. Open the attribute table for the “Reclassify” Reclassify layer and note the ‘Count’ Count of cells with a value of 0.
  2. Now open the attribute table for the “FlowlineReclass” FlowlineReclass layer and note the ‘Count’ Count of cells with a value of 0.

Notice that, although the visual geometry of the two layers has changed (one is a rectangle, and one is the shape of the subbasin), the total number of cells has not changed. ArcGIS has not automatically updated the attribute table for the clipped raster.

  1. At the top left of the Geoprocessing pane, click the Back button.
  2. In the search box, type "build raster".
  3. Click the 
  4.  Click the ArcToolbox tab
  5. Collapse the Raster Processing toolset and open the Raster Properties toolset à Build Raster Attribute Table tool tool.
  6. For 'Input Raster', select the FlowlineReclass Drag in the “FlowlineReclass” layer and click Run.
  7. Now open the “FlowlineReclass” layer again Once again, open the attribute table for the FlowlineReclass layer and note that the number of cells that have been assigned a 0 have decreased to reflect the clipped geometry.
  8. Close all attribute tables.
  9. In the Contents pane, remove the Reclassify layer.Remove “Reclassify”

Now all cells that were previously assigned a value of NoData within the subbasin geometry have been assigned a value of 0.  This will allow you to perform uniform mathematical operations across the entire subbasin in the future.

 

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Calculating Euclidean distances

Next, you will create a new raster where the value of the cell indicates the distance in feet to the nearest flowline.

  1. At the top left of the Geoprocessing pane, click the Back button.
  2. In the search box, type "euclidean".
  3. Click the Euclidean Distance 
  4. Click the Toolbox icon.
  5. Within the Spatial Analyst Tools toolbox, collapse the Reclass toolset.
  6. Double-click the Distance toolset à Euclidean Distance tool.
  7. For ‘Input raster or feature source data’, drag in the select the Flowlines_StatePlane layer from the Table of Contents.
  8. For ‘Output distance raster’, rename the raster from “EucDist“EucDist_Flow1” to “FlowlineDistance”Flow1” to “FlowlineDistance”.
  9. Click the Environments… button the Environments tab.
  10. For Processing Extent, use the ‘Extent’ drop-down menu to select Same as layer DEMft.Use the ‘Snap Raster’ drop-down menu to select the DEMft raster'Extent', select Same As layer: DEMft.
  11. For ‘Cell Size’, select Same as layer DEMft.
  12. For ‘Snap Raster’, select the DEMft raster.

In order to output a raster with the desired geometry (in this case the same as DEMft or subbasin) of the subbasin, you must apply a mask.   Without a mask, the output raster will be a rectangle that contains containing the subbasin geometry., as seen before.

  1. For 'Mask’, Use the ‘Mask’ drop-down menu to select the Subbasin_StatePlane layer.
  2. Click the Parameters tab.
  3. Ensure your Geoprocessing pane Go back to Parameters, ensure your ‘Euclidean Distance’ window appears as shown below and and click Run.
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  4. In the Contents pane, rightRight-click the FlowlineDistance layer and click select Symbology.Select Quantile for Method and 5 for classes.
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  5. For 'Primary symbology', select Classify.
  6. For 'Method', select Quantile.
  7. For 'Classes', select 5.

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You should now see cells that vary in color the farther away they are from the nearest flowline.

 

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Performing map algebra

 

Finally, you are ready to perform the reconditioning step. You can think of this as digging a trench with a funnel-shaped cross-section along each flowline to ensure that water will flow in the intended direction. The math behind this step is explained in the diagram below and all units are in feet, since the State Plane Texas South Central project stores XY coordinates in feet and since you also recalculated the Z elevations in Lab 2 in feet.

 

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  1. Click Tools.
  2. Within the Spatial Analyst Tools toolbox, collapse the Distance toolset.
  3. Double-click the Map Algebra toolset à Raster Calculator tool.

 

  1. At the bottom of the Symbology pane, click the Geoprocessing tab..
  2. At the top left of the Geoprocessing pane, click the Back button.
  3. In the search box, type "calculator".
  4. Click the Raster Calculator (Spatial Analyst Tools) tool.

When entering expressions in the raster calculator, your syntax When entering expressions in the raster calculator, your syntax must be exact, so though you could technically type in the equation below, we’d recommend entering everything by clicking the mouse, so you do not get any syntax errors (at least until you’ve learned the proper syntax).

  1. By double-clicking the layer names and single-clicking the calculator buttons'Raster' layer names and 'Tools' operations and typing the numbers, enter the following equation: "DEMft" - 30 * "FlowlineReclass" - 0.02 * (1500 - "FlowlineDistance") * ("FlowlineDistance" < 1500).
  2. For ‘Output raster’, rename the raster from “demft“demft_raster” to “DEMRecon”raster” to “DEMRecon”.
  3. Ensure your ‘Raster Calculator’ window your Geoprocessing pane appears as shown below and click Run.
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You should notice Notice that the DEMRecon layer looks very similar to the original DEMft. To better understand the difference between the two, you will actually calculate the difference between their corresponding values.

  1. Click the ArcToolbox tab.
  2. Double-click the Raster Calculator tool againIn the geoprocessing pane, delete all text from the 'Map Algebra expression' box.
  3. Using the same clicking technique as before, enter the following equation: "DEMft” – “DEMRecon”DEMft” – “DEMRecon”.
  4. For ‘Output raster’, rename the raster from DEMRecon to “DEMDiff”“DEMDiff”.
  5. Ensure your ‘Raster Calculator’ window your Geoprocessing pane appears as shown below and click Run.
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The DEMDiff layer displays the amount of "earth" that has been removed through the reconditioning process.

 

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Part 3: Analyzing Hydrologic Terrain

You will now undertake a series of geoprocessing steps to understand where water will flow and how much will accumulate. Essentially, you will be learning how to create flowlines and watershed boundaries, similar to those you downloaded from NHDPlus, based on DEM data.

Filling topography sinks

The Fill tool fills sinks in the DEM raster to remove small imperfections in the data. If cells with higher elevations surround a cell, the water gets trapped in that cell and cannot flow. The Fill tool modifies the elevation of the original DEM to eliminate these problems.

 

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  1. At the top left of the Geoprocessing pane, click the Back button.
  2. In the search box, type "fill".
  3. Click the Fill tool
  4. Click Tools from Analysis tab.
  5. Within the Spatial Analyst Tools toolbox, double-click the Hydrology toolset à Fill tool.
  6. For ‘Input surface raster’, drag in the select the DEMRecon layer from the Table of Contents.
  7. For ‘Output surface raster’, rename the raster from “Fill“Fill_DEMReco1” to “FIL”DEMReco1” to “FIL”.
  8. Ensure your ‘Fill’ window your Geoprocessing pane appears as shown below and click Run.
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Calculating flow direction

Now you will calculate the cardinal direction in which water from each cell is expected to flow based on the elevations of surrounding cells. Each direction is assigned one of 8 integer values between 1 and 128 as indicated in the illustration below.

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  1. At the top left of the Geoprocessing pane, click the Back buttonClick Tools from Analysis tab.
  2. In the search box, type "flow".
  3. Click the Flow Direction tool Hydrology toolset, double-click the Flow Direction tool.
  4. For ‘Input surface raster’, drag in the select the FIL layer from the Table of Contents.
  5. For ‘Output flow direction raster’, rename the raster from “FlowDir“FlowDir_FiIL1” to “FDR”FiIL1” to “FDR”.
  6. Ensure your ‘Flow Direction’ window your Geoprocessing pane appears as shown below and click Run.
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The result may appear a bit strange at first, due to the color scheme assigned to each cardinal direction.

 

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  1. Symbolize the FDR layer using Unique Values with a smooth black and white gradient for the Color Scheme.

You will notice the layer now looks more similar to a hillshade or 3D terrain visualization.

 

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Calculating flow accumulation

Finally, you will calculate flow accumulation in each cell from the cells upstream, as illustrated below. Flow accumulation is dependent on the flow direction you calculated previously.

 

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  1. Return to the Geoprocessing pane.
  2. At the top left of the Geoprocessing pane, click the Back button.
  3. In the search box, type "flow".
  4. Click the Flow Accumulation 
  5. Click Tools from Analysis tab.
  6. In the Hydrology toolset, double-click the Flow Accumulation tool.
  7. For ‘Input flow direction raster’, drag in the select the FDR layer from the Table of Contents.
  8. For ‘Output accumulation raster’, rename the raster from “FlowAcc“FlowAcc_FDR1” to “FAC”FDR1” to “FAC”.
  9. Ensure your ‘Flow Accumulation’ window your Geoprocessing pane appears as shown below and click Run.

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  2. Turn off the Flowlines_In the Contents pane, uncheck the Flowlines_StatePlane layer to better see the FAC layer.
  3. Right-click the FAC layer and click the select Symbology.
  4. For ‘Symbology’, use drop-down menu to select ‘Primary symbology’, select Classify.In the ‘Method’ drop
  5. -down menu to For ‘Method’, select Equal Interval.
  6. Use the ‘Classes’ drop-down menu to select 8 classes.
  7. Click the Classify… button.
  8. For ‘Classes’, select 8.
  9. In the 'Classes' tableFor ‘Class Breaks’, double-click the numbers in the Upper Value column  and column and typethe following list: 100, 300, 1000, 3000, 10000, 30000, 100000. (Leave the final max value, 351408 as is.)
  10. Click OK.
  11. Use the ‘Color Ramp’ drop-down menu to select the multipart color schemeFor ‘Color scheme’, scroll down to the very bottom and select the Yellow-Green-Blue (Continuous) color scheme, as shown below.


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Visually trace along the streams until you find the darkest path exiting the watershed. Notice that, according to the model you have just generated, the Buffalo-San Jacinto basin drains north into Lake Houston, instead of south into Galveston Bay. Look for the exact point on the map where this divergence is created. It is circled in the image below. A problem is that the topography in that area is extremely flat and, rather than a single well-defined channel, there are wide bodies of water connecting the bayous to Galveston Bay. Calculating the flow accumulation more accurately would require further editing the base raster so that the wide flat bodies of water are not treated as narrow flowlines. This example also illustrates how you must always double-check the results of your models to ensure they make sense. For the purposes of learning the remaining geoprocessing tools in this lab, you will continue with the existing flow accumulation model, as if it was correct.

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generated, the Buffalo-San Jacinto basin drains southeast into Galveston Bay.

  1. Zoom in to the southeastern outlet point, as indicated below, so that you can see the individual pixels.

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Creating and editing feature classes

You will now create a new point feature class to store the outlet point you just identified.

  1. Click At the bottom of the Symbology pane, click the Catalog tab.
  2. Right-click the Lab1 HydrologyLab.gdb geodatabase and select New àFeature Class… New > Feature Class.
  3. For ‘Name’, type “Outlet”.
  4. For ‘Feature Class Name’, type “Outlet”.
  5. Use the ‘Geometry Type’ drop-down menu to select Point.
  6. For Coordinate System, select Current Map.
  7. Click Run.
  8. Type’, select Point.
  9. At the bottom, click Next.
  10. Click Next again.
  11. For 'Current XY', ensure NAD 1983 StatePlane Texas S Central FIPS 4204 (US Feet) is selected.
  12. Click Finish.
  13. In the Catalog pane, drag the newly created Outlet feature class into the Lab3 map view.
  14. On the ribbonOn the Standard toolbar, click the Edit tab and click the Create button.
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  15. On the Create Features pane, select the Outlet layer and click Point. Click à button.



  16. In the Map Displaymap view, click near the center of the outlet pixel to draw a point there.



  17. On the Editor toolbarribbon, click the Save button.

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  18. When asked if you want to save your all edits, click Yes.
  19. Close the Editor toolbar and the Create Features tab.

Delineating watersheds

Now you will delineate the watershed that flows to the outlet point.

 

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  1. At the bottom of the Create Features pane, click the Geoprocessing tab.
  2. At the top of the Geoprocessing pane, click the Back button.
  3. In the search box, type "watershed".
  4. Click the Watershed (Spatial Analyst Tools)
  5. Click Tools from Analysis tab.
  6. In the Hydrology toolset, double-click the Watershed tool.
  7. For ‘Input D8 flow direction raster’, select the FDR layer from the drop-down menu raster.
  8. For ‘Input raster or feature pour point data’ select the Outlet layer from the drop-down menu.
  9. For ‘Output raster’, rename the raster from “Watersh“Watersh_FDR1” to “Watershed”FDR1” to “Watershed”.
  10. Ensure your ‘Watershed’ window your Geoprocessing pane appears as shown below and clickRun.
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  2. In the Contents pane, right-click the Watershed layer and select Zoom To Layer.

You can toggle the Subbasin_StatePlane layer on and off. Notice that the watershed boundary you have created Notice that this is very close, but does not exactly match the boundaries of the subbasin you were originally provided from NHDPlus.

 

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  1. In the Table of Contents pane, turn off all layers beneath the Watershed layer, so that only the cells within the newly defined subbasin are visible.

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Now that you have delineated the subbasin boundaries, you will generate flowlines. The number of flowlines that are generated will depend upon the flow accumulation threshold you select in separating a flowline cell from a non-flowline cell. For the purposes of this lab, you will select a threshold of 3000.

  1. Click Tools from Analysis tabAt the top left of the Geoprocessing pane, click the Back button.
  2. In the Map Algebra toolset, double-click the search box, type "calculator".
  3. Click the Raster Calculator (Spatial Analyst Tools) Raster Calculator tool.
  4. Using the same clicking technique as before, enter the following equation:    ("FAC" > 3000) & ("Watershed" > 0).
  5. For ‘Output raster’, rename the raster from “fac_rasterca” to “Streams”“fac_rasterca” to “Streams”.
  6. Ensure your ‘Raster Calculator’ window your Geoprocessing pane appears as shown below and click Run.
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Again you should have a binary raster, where flowline cells are assigned a value of 1 and all other cells are assigned a value of 0.

 

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Now you will separate your entire raster of flowlines into individual flowline segments as illustrated below.

 

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  1. Click Tools from Analysis tabAt the top left of the Geoprocessing pane, click the Back button.
  2. In the search box, type "stream".
  3. Click the Stream Link  Hydrology toolset, double-click the Stream Link tool.
  4. For ‘Input stream raster’, select the Streams layer from the drop-down menu raster.
  5. For ‘Input flow direction raster’, select the FDR layer from the drop-down menu raster.
  6. For ‘Output raster’, rename “StreamL “StreamL_Stre1” to “StreamLinks”Stre1” to “StreamLinks”.
  7. Ensure your ‘Stream Links’ window your Geoprocessing pane appears as shown below and click Run.
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  8. Symbolize the StreamLinks layer using unique values.
  9. In the Table of Contents pane, collapse the StreamLinks symbology.


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Delineating catchment basins

Now you will delineate the catchment basin associated with each stream link. These catchment basins are similar to the subwatersheds you downloaded from NHDPlus.

  1. Return to the Geoprocessing pane.
  2. At the top left of the Geoprocessing pane, click the Back button.
  3. In the search box, type "watershed".
  4. Click the Watershed (Spatial Analyst Tools)
  5. Click Tools from Analysis tab.
  6. In the Hydrology toolset, double-click the Watershed tool.
  7. For ‘Input D8 flow direction raster’, select the FDR layer from the drop-down menu raster.
  8. For ‘Input raster or feature pour point data’ select the StreamLinks layer from the drop-down menu.
  9. For ‘Output raster’, rename “Watersh “Watersh_FDR2” to “Catchments”FDR2” to “CatchmentsRaster”.
  10. Ensure your ‘Watershed’ window your Geoprocessing pane appears as shown below and click Run.
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  11. Symbolize the Catchments CatchmentsRaster layer using unique values.Image Removed
  12. In the Table of Contents pane, collapse the Catchments CatchmentsRaster symbology.

Converting rasters to features

Now you will convert the Catchments CatchmentsRaster raster into a polygon feature class.

  1. Return to the Geoprocessing pane.
  2. At the top left of the Geoprocessing pane, click the Back button.
  3. In the search box, type "raster to polygon".
  4. Click the Raster to Polygon 
  5. Click Tools from Analysis tab.
  6. Double-click the Conversion Tools toolbox à From Raster toolset à Raster to Polygon tool.
  7. For ‘Input raster’, select the Catchments layer from the drop-down menu CatchmentsRaster layer.
  8. For ‘Output polyline features’, rename “RatsterT “RatsterT_Catchme1” to “CatchmentPoly”Catchme1” to “CatchmentsPoly”.
  9. Uncheck Simplify polylinespolygons.
  10. Ensure your ‘Raster to Polygon’ window your Geoprocessing pane appears as shown below and click Run.
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  11. Symbolize the CatchmentPoly layer using unique values with ID as the value field.
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  12. In the Table of Contents pane, collapse the CatchmentPoly symbology.

Now you will also convert the raster StreamLinks into a polyline feature class. While you could use the Raster to Polyline tool, you will instead use a tool in the Hydrology toolset, designed specifically for converting raster stream links into polyline features. The difference between the two methods is illustrated below.

 

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  1. Return to the Geoprocessing pane.
  2. At the top left of the Geoprocessing pane, click the Back button
  3. Click Tools from Analysis tab.
  4. Collapse the Conversion Tools toolbox.
  5. In the search box, type "stream".
  6. Click the Stream to Feature  Hydrology toolset, double-click the Stream to Feature tool.
  7. For ‘Input stream raster’, drag in the StreamLinks layer from the Table of Contents select the StreamLinks raster.
  8. For ‘Input flow direction raster’, drag in the FDR layer from the Table of Contents select the FDR raster.
  9. For ‘Output polyline features’, rename the feature class from “StreamT“StreamT_StreamL1” to “DrainageLines”StreamL1” to “DrainageLines”.
  10. Uncheck Simplify polylines.
  11. Ensure your ‘Stream to Feature’ window your Geoprocessing pane appears as shown below and click Run.
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Calculating Strahler stream order

Now you will use the Strahler method to assign a flow hierarchy to the stream links as illustrated below.

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  1. At the top left of the Geoprocessing pane, click the Back buttonClick Tools from Analysis tab.
  2. In the search box, type "stream".
  3. Click the Stream Order  Hydrology toolset, double-click the Stream Order tool.
  4. For ‘Input stream raster’, select the Streams layer from the drop-down menu raster.
  5. For ‘Input flow direction raster’, select the FDR layer from the drop-down menu raster.
  6. For ‘Output raster’, rename the raster from “StreamO“StreamO_Stre1” to “StrahlerOrder”Stre1” to “StrahlerOrder”.
  7. Ensure your ‘Stream Order’ window your Geoprocessing pane appears as shown below and click Run.
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  8. In the Table of Contents pane, turn off all layers except for the new StrahlerOrder layer, so that its symbology is more apparent.

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Calculating zonal statistics

Now you would like to append this Strahler order to the attribute table of the DrainageLines vector layer, so that you may symbolize that layer using graduated symbols according to the Strahler order number. First, you will need to create a table indicating the Strahler order of each stream.

  1. Click Tools from Analysis tabAt the top left of the Geoprocessing pane, click the Back button.
  2. In the search box, type "zonal statistics".
  3. Click the Zonal Statistics as Table (Spatial Analyst) tool Spatial Analyst Tools toolbox, double-click the Zonal toolbox à Zonal Statistics as Table.
  4. For ‘Input raster or feature zone data’, select the StreamLinks layer from the drop-down menu.
  5. Use the For ‘Zone field’ drop-down menu to , select the Value field.
  6. For ‘Input value raster’, select the StrahlerOrder layer from the drop-down menu raster.
  7. For ‘Output table’, rename the table from “ZonalSt“ZonalSt_StreamL1” to “OrderTable”StreamL1” to “OrderTable”.
  8. Ensure your ‘Zonal Statistics as Table’ window your Geoprocessing pane appears as shown below and click Run.
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Adding a new field to an attribute table

Now you will create a new field in the DrainageLines attribute table to store the Strahler order number.

  1. Open the DrainageLines attribute table.
  2. At the top of the DrainageLines attribute table, click the Add Field button.

 


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  2. In the bottom row of the table, for ‘ Field NameFor ‘Name:’, type “StrahlerOrder” “StrahlerOrder”.
  3. Use the ‘Type‘Data Type:’ drop-down menu to select Short Integer for short integer.
  4. Ensure your ‘Add Field’ window Fields table view appears as shown below and click Save on top of  the main tab.

 

 

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  2. On the ribbon, under the Fields tab, click the Save button.

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  3. Close the Fields table view.

Notice the Scroll all the way to the right and notice the new StrahlerOrder field has been added to the end of the DrainageLines attribute table. All of the values are currently null, but will later be populated with the Strahler Order integers from the OrderTable.

 

 

Joining tables

You are now ready to join the OrderTable to the DrainageLines layer based on their common identification fields.

  1. Click At the top right of the DrainageLines attribute table, click the Table Options button and select Joins and Relates > Add Join…Join.

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  2. For ‘Input Join Field’, select the grid_code field.
  3. For ‘Join Table’, select the OrderTable table.
  4. For ‘Output Join Field’, select the VALUE Value field.
  5. Ensure that the ‘Join Data’ your Add Join window appears as shown below and click Run OK.

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Scroll across the table and notice that most of the statistics (Min, Max, Mean, Majority, Minority, Median) are the same and all contain the Strahler order integer, so it doesn’t matter which field you copy, though you will choose the MIN field for this lab.

  1. In the attribute table, right-click on the StrahlerOrder field header and select Calculate Field…Field.
  2. Scroll down the list of ‘Fields:’ ‘Fields’ and double-click the OrderTable.MINORITY field MIN field and click RunOK.
  3. Scroll down the newly populated StrahlerOrder field and notice the values of 1, 2, and 3 corresponding to Strahler order value.

Since you have copied the Strahler order into a field in the original DrainageLines attribute table, you You no longer need the tabular join.

  1. Again, click the Table Options button and select Joins and Relates > Remove Join(s) à Remove > Remove All Joins.
  2. When asked if you are sure you want to remove all joins, click Yes.
  3. Symbolize the DrainageLines layer using graduated symbols based on the StrahlerOrder field.
  4. In the Table of Contents pane, turn on only the Outlet, DrainageLines, and CatchmentPoly, layers and turn offall other layers.

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FOR MAP LAYOUT TO BE TURNED IN

Create an 8.5 x 11 layout showing the vector catchment basins along with the stream links symbolized using graduated symbols according to their Strahler order and the outlet point that you used.

 

 

Deliverables

  1. An exported map of Create an 8.5 x 11 layout showing the DEMRecon layer turned on.
  2. Create an 8.5 x 11 layout showing the vector catchment basins along with the stream links symbolized using graduated symbols according to their Strahler order and the outlet point that you used.