Creating a zone or district map layer that merges county boundaries.
Build a zone or district layer for a disaster relief operation (DRO) using only ArcGIS Online (AGOL) — no ArcGIS Pro, and minimal credits.
Recipe by Marty Malley — Disaster Services Volunteer, North Central Division
01
Scenario
Often in a large disaster response operation (a DR — each operation carries a DR number like DR492-27) there is a need to divide the response area into districts or zones, and a map layer is needed to show them. Very commonly, the zones or districts involve collections of counties. This mapper aid describes the process a mapper can use to create a zone or district map layer in ArcGIS Online (AGOL) — without needing to use ArcGIS Pro, and consuming minimal credits.
If your zones or districts don't follow county lines, you will need a more sophisticated approach than this one, and probably need to use ArcGIS Pro.
02
Approach
Four moves, all inside ArcGIS Online.
Open the US_Counties_Red_Cross_DRO_Zones layer in a new map.
Select all of the counties that are in the DR response area using a filter.
Annotate those counties with the zone (or district) name and DRO number.
Use the Dissolve tool to create a zone (or district) layer. Note: this may require a Publisher license.
03
Filter The Counties
Pull up the national county layer and narrow it to just your operation's counties.
From your My Content page, click My Organization and search for US_Counties_Red_Cross_DRO_Zones. Open it in Map Viewer.
Go to the layer list and highlight the layer.
On the right side of the page click the Filter icon. When the Filter panel opens click Add New.
For Condition select County and State then Includes. Use the Select Values dropdown to select all of the correct counties for the DR. The Search box is your friend. The Includes clause should contain a list of all of the state/county pairs. Select Save.
The map should immediately filter to the counties you selected. Confirm that it looks right and there are no dangling counties.
Walkthrough coming. A short animated capture of this step group will appear here after the first recording session.
04
Tag Zone Name And DR Number
Open the table and label each county with its zone and operation.
In the Layers list on the left, click the 3 dots and then Show Table. The data table should open showing only the counties you selected.
Edit the table, applying a zone name (e.g. Zone A, Zone B) to each county.
Apply the DR number (e.g. DR492-27) to each county. If desired, apply an optional zone label and notes to each county.
These edits are immediately applied to the feature layer. You now have a filtered layer with all of the counties for your DR.
Shared layer. These edits change the shared national layer for everyone. Coordinate with other active operations, and clear your zone tags when the operation closes.
Walkthrough coming. A short animated capture of this step group will appear here after the first recording session.
05
Run Dissolve
Merge the tagged counties into one polygon per zone.
Click the Analysis Tools icon in the right tool bar.
In the search bar type Dissolve — select the Dissolve Boundaries tool.
In the Input Features box select the counties layer.
Enable Dissolve Features with Matching Field Values and Create Multipart Features.
In the Output Name box put something like DR492_27_Zones (using your DR number), select a folder where you want it to go, and click Estimate Credits — it should be a tiny number, like way less than 1. Click Run.
It will take a little while to run, but when it is done, you will have a new zone layer on the map and in the folder you sent it to. I recommend then opening the new feature layer and setting the Visualization the way you want it.
Add it to your DR situational awareness map.
Bonus: you can use the filtered county layer to label the counties on your situational awareness map. Just filter it using the DR number and symbolize it as you see fit. This is a simpler county layer than Master ARC Geography, which carries a large number of attributes.
License check. Dissolve needs a Publisher role and a small number of credits. If you don't have that role, use the toolkit below — it produces the same zone layer with no credits and no Publisher license.
Walkthrough coming. A short animated capture of this step group will appear here after the first recording session.
06
Watch It Done
Demo video coming. A 2-minute recording of this whole recipe, start to finish, will appear here after the first recording session.