Create a layer for the storm drain

To find the area that contributes to the storm water system, you need to start by identifying the location of the storm drain. You'll create a layer on your map that will mark the location of the storm drain. You can complete this lesson using ArcGIS Online or ArcGIS Enterprise, depending on your configuration.

Create a map

You'll create your map by signing in and navigating to an area of interest.

  1. Sign in to your ArcGIS organizational account or into ArcGIS Enterprise using a named user account.
    Note:

    If you don't have an organizational account, you can sign up for an ArcGIS free trial.

  2. On the ribbon, click Map.

    Map

    A new map opens.

    Note:

    The default basemap is Topographic, but your map may have a different basemap depending on your organization's settings.

    Default map

Find the school

You'll find the school by typing its name in the search box.

  1. On the ribbon, in the search box, type Blackman Elementary, which was randomly chosen for this analysis. In the list of suggested locations, click Blackman Elementary School, 586 Fortress Blvd, Murfreesboro, TN, 37128, USA.

    Search name

    Note:

    Some ArcGIS organizations have custom address locators. You may encounter different search results than those in the example image.

    The map zooms to the school. A Search result pop-up confirms the location.

    School location

  2. Close the Search result pop-up.

Use a different basemap to find the nearby storm drain

You can't see the school or any nearby storm drains on your map, but if you use a different basemap that shows satellite imagery, you can. You want imagery that may be more clear than what's available in the basemap gallery and you want a reference layer to provide context and labels for the imagery. You'll browse ArcGIS Living Atlas of the World for these layers and use them for your basemap.

Tip:

To learn more about using ArcGIS Living Atlas layers as basemaps, see the Configuring custom basemaps using ArcGIS Living Atlas layers blog article.

  1. On the ribbon, click Add and choose Browse Living Atlas Layers.

    Browse Living Atlas Layers option

    The search pane appears.

  2. In the search box, type World Imagery (Clarity).
  3. Confirm that Living Atlas is displayed at the top of the pane and press Enter.

    Search for World Imagery (Clarity)

  4. For the World Imagery (Clarity) layer, click the title.

    Open details for World Imagery (Clarity)

    The item details pane appears.

  5. Click Use as Basemap.

    Use World Imagery (Clarity) as the basemap

  6. In the search box, clear your previous text and type Hybrid Reference Layer.
  7. For Hybrid Reference Layer, click the Add button.

    Add Hybrid Reference Layer

  8. In the search pane, click the Back button. If necessary, click Content.

    You return to the Contents pane. It lists the layers on the map, including your new basemap.

    Layers in the Contents pane

    You will move the Hybrid Reference Layer to your basemap and set it as a reference layer. Setting the Hybrid Reference Layer as a reference layer ensures that the labels always appear above your data as reference, no matter what data you add to the map.

  9. In the Contents pane, point to Hybrid Reference Layer, click the More Options button, and click Move to Basemap.

    Move Hybrid Reference Layer to basemap

    The Hybrid Reference Layer is moved to the World Imagery (Clarity) basemap.

    World Imagery (Clarity) basemap layers
  10. Point to Hybrid Reference Layer again, click the More Options button, and click Set as Reference Layer.

    The Hybrid Reference Layer icon changes to indicate its being used as a reference layer.

    Hybrid Reference Layer set as reference layer

    The map is updated to show an image of the school building and the surrounding area.

    Map of school and surrounding area

  11. Zoom in and pan to the south (down) along the road that passes to the west of the school until you see where the drainage ditch passes under the road as shown below:

    Find storm drain on map

    Now that you know where the storm drain is, you’ll create a layer for it on the map. The layer you create will be used to find the upstream watershed and the downstream flow path for the storm drain.

Create a new layer

You'll create a new layer for the storm drain layer by adding a point to the map. To add the point, you'll use a Map Notes layer.

  1. On the ribbon, click Add and click Add Map Notes.
  2. For the name, type Storm Drain.

    Add Map Notes window

  3. Click Create.

    In the Add Features pane, you can choose a symbol to show the storm drain location.

  4. In the Add Features pane, click the Pushpin symbol and click the storm drain location on the map.

    Pushpin symbol

  5. Change the title to Storm Drain and the description to Storm drain near Blackman Elementary School.

    Map Notes info

  6. So that you can see the symbol more easily, click Change Symbol.
  7. Change the style category from Shapes to Basic.

    Basic style

  8. Scroll down and click the yellow pushpin symbol to select it.

    Yellow pushpin

  9. Click OK. Click Close.

    Pushpin location

  10. Click the arrow at the upper right of the Add Features pane to close it.

    Close pane

Save the map

Before proceeding with the analysis, save your map.

  1. On the ribbon, click Save and choose Save.

    Save

  2. In the Save Map window, for the title, type Storm Drain Analysis.
  3. For the tags, type storm drain, watershed, flow path, and trace.
    Tip:

    Separate the tags with commas.

  4. For the summary, type Watershed and flow path analysis for storm drain near Blackman Elementary School.

    Save Map

  5. Click Save Map.

You've made a layer for the storm drain.


Create watersheds for the storm drain

Previously, you identified a storm drain and created a layer to store its location. Next, you'll use the Create Watersheds tool to create watersheds, or upstream contributing areas, for the point in the storm drain layer.

Create a default watershed

You'll first create a watershed by keeping all the default parameters in the tool.

  1. If necessary, open your Storm Drain Analysis map.
  2. In the left pane, click the Content button so you can see all the layers on the map.
  3. In the Contents pane, point to the Storm Drain layer and click the Perform Analysis button.

    Perform Analysis

  4. In the Perform Analysis pane, click Find Locations and choose Create Watersheds.

    Create Watersheds

    Note:

    If you are using your Enterprise account, this tool may not be available. Your portal administrator must enable services in your portal. The two services that are required for this tool are the Esri World Elevation Service and the Esri Hydrology Service. Once the services are enabled, the tool will be ready for use.

  5. Change Result layer name to Default Watershed and add your name or initials to make your layer unique in the organization.
  6. If necessary, uncheck the Use current map extent box.

    Result layer name

  7. Click Run Analysis.

    When the analysis is completed, two layers are added to the map and appear in the Contents pane—one with the default watershed and another with adjusted points used to compute the watershed.

    Watershed results on the map
    Note:

    To find the watersheds, the analysis points are adjusted so they fall precisely on a drainage line. The adjusted locations are written to the Adjusted Points output layer.

  8. In the Contents pane, point to the Default Watershed layer. Click the More Options button and choose Zoom to.

    Zoom to layer

  9. If necessary, zoom out one level so you can see the entire watershed area.
  10. Click the watershed to see its pop-up.

    Small watershed pop-up

    As you can see from the information in the pop-up, the size of this watershed is quite small (0.02 square miles or 0.05 square kilometers). These results are not unusual. If your analysis point is located away from a drainage line, the resulting watershed is likely to be very small and not of much use in determining the upstream source of contamination. In most cases, your analysis point should be positioned on the nearest drainage line to find the watershed that flows to a point on the drainage line. To find the closest drainage line, you can specify a search distance, which is what you’ll do in the next section.

    The results of this tool should be used to provide a regional understanding of the watershed rather than identify the exact location of the watershed at local scales. You'll do that next.

Create an upstream watershed

Next, you'll create a larger upstream watershed by specifying a search distance.

  1. Run the Create Watersheds analysis again.
    • Use a search distance of 0.5 miles.
    • Change the result layer name to Upstream Watershed (add your name or initials).
    • If necessary, uncheck the Use current map extent box.

    Create Watersheds pane

    When the analysis is completed, you’ll see that another watershed has been added to the map that encompasses nearly the entire smaller watershed.

    Two watersheds

  2. Turn off the Default Watershed and Default Watershed - Adjusted Points layers.
  3. Zoom to the Upstream Watershed layer and click the watershed to see that it's much larger, covering more than 21 square miles (55 kilometers).

    Watershed results

    The underlying data to this lesson is updated periodically so your numbers could vary.

  4. Close the pop-up.
  5. Press Shift while you draw a box on the map around the storm drain point and the adjusted point at the northern extent of the watershed.

    The map zooms in to that area.

  6. On the ribbon, click the Measure button and click the Distance button.
  7. On the map, first click the point you created, and double-click the adjusted point to find the distance between the two.

    Measure tool

    Note that the distance is less than the 0.5-mile value you input before you ran the tool.

  8. Click the close button at the upper right of the Measure window to close it.
  9. Save the map.

You've identified where the water in the storm drain comes from.


Find the downstream flow path from the storm drain

Previously, you identified where the water in the storm drain comes from. Next, you'll create a trace, or flow path, in a downstream direction from the point in the storm drain layer.

Perform the analysis

You'll use the Trace Downstream tool to find the downstream flow path.

  1. If necessary, open your Storm Drain Analysis map.
  2. In the Contents pane, point to the Storm Drain layer and click the Perform Analysis button.
  3. In the Perform Analysis pane, click Find Locations and choose Trace Downstream.
  4. In the Trace Downstream pane, change Result layer name to Storm Drain Trace (add your name or initials).
  5. If necessary, uncheck the Use current map extent box.

    Trace Downstream pane

    Note:

    If you are using your Enterprise account, this tool may not be available. Your portal administrator must enable services in your portal. The two services that are required for this tool are the Esri World Elevation Service and the Esri Hydrology Service. Once the services are enabled, the tool will be ready for use.

  6. Click Run Analysis.

    When the analysis is completed, the trace line is added to the map and appears in the Contents pane.

    Trace Downstream results

    When you're zoomed in, the trace line is angular and does not appear to align well with Puckett Creek, which flows through the treed area to the north. As with the watershed, at these large map scales, the trace on the map does not give you a good idea of the real flow path. In urban and suburban environments, the flow path is often determined by human constructs, such as drainage ditches, concrete channels, and culverts, which allow water to flow under roads, railroads, and other obstructions. Often, these are not visible in the landscape, as they've been constructed underground.

Explore the length of the trace

Next, you'll explore the length of the trace.

  1. To better see the trace, turn off all the watershed result layers.
  2. To see the entire flow path, zoom to the Storm Drain Trace layer.

    Trace downstream

  3. To see how long the path is, in the Contents pane, point to the Storm Drain Trace layer and click the Show Table button.

    Show Table button

    The trace is more than 1,200 miles long.

    Tip:

    The area units shown in tools and tables are set in your ArcGIS organizational account or your personal profile. Because there is no way to change the units in the table's field, you can either change your profile and rerun the analysis, or add a new field to the table and calculate it to show the length in the desired units. For example, you'd multiply miles by 1.609344 to get kilometers, and kilometers by 0.6213711922 to get miles, adjusting the number of decimal points depending on how precise you want the measurements to be. This is what you’ll do in this lesson to calculate kilometers.

    Results table

    Note:

    Your results may differ slightly.

    To find and show this distance in kilometers, you'll first add a new field to the table.

  4. In the Table pane, click the Options button and choose Add Field.

    Add Field

  5. In the Add Field window, for Name, type LengthKilometers, and for Display Name, type Length in Kilometers. Change Type to Double (for numbers with decimal places).

    Add Field dialog box

  6. Click Add New Field.
  7. In the table, scroll to the right, click the Length in Kilometers field heading, and choose Calculate.
    Note:

    If you don't see the new field in the table, click the Options button, choose Show/Hide Columns, and check the Length in Kilometers box.

    Calculate

  8. In the Calculate Field window, click SQL.

    When calculating fields you can write an expression using Esri's Arcade language, or using SQL. SQL is more appropriate for this expression because you are writing a basic calculation.

  9. In the Calculate Field window, in the Fields list, click AnalysisLength.

    AnalysisLength option in the Fields list

    This is the true name of the field, but the alias, Length Miles, is what's shown when the table is displayed.

  10. Continue building the expression by clicking the multiplication button (*) and typing 1.609.
  11. Click the Validate button to verify that the expression was entered correctly.

    Validate button in the Calculate Field window

  12. Click Calculate.
  13. Check the results to see that the length in kilometers is approximately 2,045 kilometers.

    Length in Kilometers

  14. Click the close button at the upper right of the table to close the table view.
  15. On the ribbon, click Basemap and choose Topographic.

    Topographic option in the basemap gallery

  16. Save the map.
  17. Take a few minutes to pan and zoom, exploring the flow path on the map.

    Explore map

    From the storm drain, the flow path enters Puckett Creek, which connects downstream to the Cumberland River. The path meanders west through Nashville, and then flows north to connect with the Ohio River. Once it connects to the Mississippi River, the path flows to New Orleans and enters the Gulf of Mexico at the mouth of the Mississippi. In all, it touches the border of or passes through seven states, two major rivers, two large lakes, and a number of smaller lakes and rivers.

You've identified where the water for a storm drain in Tennessee comes from and where it will enter the Gulf of Mexico.


Share your map with others

Previously, you completed the downstream trace analysis. Now, you'll share your results with others. Before sharing your map, you'll make a few edits to clean it up, which can include setting the map extent, renaming layers, removing layers, and changing symbols.

Clean up the map

First, you'll make some changes to the map to clean it up.

  1. If necessary, open your Storm Drain Analysis map.
  2. Zoom to the Storm Drain Trace layer.
  3. In the Contents pane, point to the Storm Drain Trace layer. Click the More Options button and choose Rename.
  4. For Layer Name, type Downstream Flow Path.

    Rename window

  5. Click OK.
  6. Change the name of the Upstream Watershed layer by removing your name.
  7. Turn on the Upstream Watershed layer.
  8. In the Contents pane, point to the Default Watershed layer. Click the More Options button and choose Remove.
  9. Also remove the two Adjusted Points layers.

    At this point, your map should appear as shown below.

    Final map

  10. In the Contents pane, point to the Upstream Watershed layer and click the Change Style button.

    Change Style button

  11. Click the arrow next to Choose an attribute to show and choose Show location only.

    Show location only

  12. On the Location (Single symbol) drawing style, click Options.

    Drawing style options

  13. Click Symbols to change the symbol.

    Click Symbols

  14. Click the blue color shown below (#0070FF) to change the fill color of the symbol.

    Choose fill

  15. Click OK.
  16. Click OK and click Done to finish changing the symbol.
  17. Save the map.

Share your map

Now that your map is in good shape, you'll share it.

  1. On the ribbon, click Share.

    Share

  2. Choose to share your map with everyone or your organization.

    Share with Everyone

  3. In the Update Sharing window, click Update Sharing.

    Update Sharing

    Tip:

    The layers in your map must have the same sharing properties as your map. Any analysis layers you create are, by default, not shared, so you're prompted to share the layers on your map.

  4. To share your map with someone by email, copy the hyperlink (web address) shown in the Link to this map box and paste it in your message to them.
    Note:

    To share your map on Facebook or Twitter, click the icons at the right, if available.

    Link to map

  5. Click Done to save your changes.

    Try repeating the analyses for other storm drains or other places in the environment where storm water and pollution can enter the storm drainage system. For example, choose a point on the Chicago River, which was reversed in 1900, to see how this river flows down to the Mississippi River and into the Gulf of Mexico rather than into Lake Michigan.

    You can also use the option in the Trace Downstream tool to split the downstream flow path into segments of a specified length. This would allow you to see more easily how long the trace was.

    Trace downstream settings

    For example, for the Chicago River flow path in an example storm drain analysis map, the length of the trace was nearly 1,500 miles (2400 kilometers). Using 500 miles as the length for each segment, you can see that the first 500 miles of the flow path extend from the point on the Chicago River to just about where the Ohio River joins the Mississippi, and the 1,000-mile mark is at about the northern border of Louisiana.

To see where storm water pollution that enters the ocean will be circulated, try the Esri Message in a Bottle app, which tracks ocean currents globally in space and time. Use the app to follow and predict the migration of a message in a bottle, pollution, or other suspended objects.

You can find more lessons in the Learn ArcGIS Lesson Gallery.