Calculate landslide potential for communities affected by wildfires

Wildfires make the landscape more susceptible to landslides when rainstorms pass through an area after wildfires. Post-fire debris flows are particularly hazardous because they can occur with little warning, can exert great impulsive loads on objects in their paths, and can strip vegetation, block drainage ways, damage structures, and endanger human life. Often there is not enough time between a fire and a rainstorm to implement an effective emergency response plan. However, various post-fire debris-flow hazard assessment models have been developed to estimate the probability and volume of debris flows that may occur in response to a storm.

For more detailed information on hazard assessment, review the following resources:

• USGS Post Wildfire Debris Flow Hazard Assessment Viewer
• Post-fire debris-flow models
• USGS site for burn area emergency response

In this tutorial, you will use ArcGIS Enterprise configured for distributed raster analysis with ArcGIS Image Server. Specifically, you'll create a landslide risk map for the Santa Rosa, California region which was devastated by a wildfire in 2017. Creating the landslide risk map uses raster function chains to derive a burn severity map, topographic slope map, and a land-cover index map, which are combined into one processing chain for ArcGIS Enterprise to execute. The use of distributed raster analysis for this workflow demonstrates how ArcGIS Enterprise can be deployed in a rapid way to process large volumes of data across a widely affected area.

This tutorial was last tested on May 26, 2023, using ArcGIS Pro 3.1 and ArcGIS Enterprise 11.1. If you're using a different version of ArcGIS Pro or ArcGIS Enterprise, you may encounter different functionality and results.

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Requirements

• ArcGIS Pro (see options for software access)
• ArcGIS Enterprise base deployment and a dedicated ArcGIS Image Server
• ArcGIS Image Server license for ArcGIS Enterprise
• Publisher or Administrator role in an ArcGIS Enterprise (learn more)

Configure the image server

Raster analytics in ArcGIS Enterprise allows you to use distributed processing to perform analysis on large image and raster collections much faster than is possible in a stand-alone GIS environment. You can also run complex, multistep raster models quickly, with the ability to publish and share results directly to your Enterprise. To perform raster analysis, you must first configure ArcGIS Image Server in your ArcGIS Enterprise.

This tutorial has the following prerequisites:

• Two licenses are required for raster analysis: ArcGIS Enterprise and ArcGIS Image Server.
• You must have configured, at minimum, a base ArcGIS Enterprise deployment. For help setting up a base deployment, see Get Started with ArcGIS Enterprise Builder.
• You must also have at least one additional server site. If you don't have an additional server site installed and configured, see Install ArcGIS Server on one machine.

• The additional server should be licensed with ArcGIS Image Server. For help, see Authorizing ArcGIS Server.

If you have administrative privileges, you can start the tutorial now. If you do not, you'll need your ArcGIS Enterprise administrator to complete this first module to configure the image server before you can begin the second module of this tutorial.

Register new data stores

Raster analysis services store raster results in a registered data store. This can be either a file share or a cloud store. For this tutorial, you’ll register two new data stores on your enterprise machine: a raster data store and a file share containing your tutorial data.

Note:

If you are using cloud stores, see the documentation on using a cloud store for your raster data store.

1. Create two folders on drive C of your enterprise machine named RasterStore and LandslideData.

   

   Next, you'll ensure that these folders are shared and accessible from all server sites.

   Note:

   ArcGIS Server Manager must be communicating over HTTPS when registering or editing a path for a raster data store.

2. Download the LandslideData.zip file and unzip its contents into the LandslideData folder created on the drive C.

   The 31 files should be located at the root of the C:\LandslideData folder, rather than inside a subfolder.

   

   If you have configured the image server to allow another member of your organization to complete the tutorial, you'll need to ensure that this person has full access to the folder. You'll configure these folders settings next.

3. From drive C, right-click LandslideData and choose Properties.
4. In the LandslideData Properties window, click the Sharing tab and click Advanced Sharing.

   

5. Check Share this folder and click Apply.

   

6. Click Permissions.

   

   Since you are registering a folder, you must grant the ArcGIS Server account permissions to these locations. The ArcGIS Server account is the account you used to install ArcGIS Server, not the primary site administrator specified when the ArcGIS Server site was created. You can find this account by searching for the Services app in the start menu and check the account running the ArcGIS Server service in the Log On As column.

7. In the Group or user names list, select the user's account. If necessary, click Add to search for and add the account before selecting it.
8. In the Permissions box, check Allow for Full Control.

   

9. In the Permissions window, click Apply and click OK.
10. In the Advanced Sharing window, click Apply and click OK.

    In the LandslideData Properties window, note the Network Path for the folder—you’ll need it when you register this folder as a data store later.

    

11. Close the LandslideData Properties window
12. Repeat steps 3 through 11 on the RasterStore folder.

    Now that you've created two folders and updated their permissions, you'll register them with ArcGIS Server using the ArcGIS Server Manager.

    Note:

    If you cannot access the folders from multiple server sites, you can copy the folders containing tutorial data to each of the server machines, and ensure that the file share containing the data is registered to each server site using ArcGIS Server Manager. Refer to the documentation for more information on registering folders on multiple ArcGIS Server sites.

13. Open ArcGIS Server Manager for the enterprise machine using an administrator account.

    Tip:

    Your ArcGIS Server Manager can be found at https://gisserver.domain.com:6443/arcgis/manager.

    If this site has ArcGIS Web Adaptor (IIS) configured, the ArcGIS Server Manager can be found here instead: http://gisserver.domain.com/webadaptorname/manager. The webadaptorname is most commonly defined as server.

14. Click the Site tab and click Data Stores.

    

15. For Register, click the drop-down list and choose Raster Store.

    

16. For Name, type RasterStore.

    This is a unique name for the registered location and should contain only alphanumeric characters and underscores.

17. If necessary, for Type, choose File Share.
18. Next to Path, specify the full path to the raster file share using the pattern \\gisserver\RasterStore. Replace gisserver with the name of the server on your enterprise machine.

    Avoid using local paths such as C:\RasterStore unless the same data folder will be available on all nodes of the server site.

19. Click Create.

    

    The raster data store you registered will now appear in the list of registered data stores. Next, you will register the location where your tutorial data is saved.

    

    Note:

    There may be different data stores in the image than what you have in your configuration.

20. For Register, click the drop-down list and choose Folder.
21. For Name, type LandslideData.
22. For Publisher Folder Path, type the folder name \LandslideData, and for Publisher Folder Hostname, type the server name using the pattern \\gisserver. Replace gisserver with the name of the server on your enterprise machine.

    

    Together, Publisher Folder Path and Publisher Folder Hostname make up a full folder path, so make sure you add slashes in the appropriate places. Like before, avoid using the local path C:\LandslideData unless the same data folder will be available on all nodes of the server site.

23. Click Create.

    The folder with your tutorial data now appears in the list of registered data stores.

    

24. Click Validate All.

    

    When your stores are validated, green check marks appear.

    

    Note:

    Next, you will create matching folders to the ones you created on the Enterprise machine on the ArcGIS Image Server machine. Only do this if those are two different machines. If your image server machine is also the Enterprise machine, then you have already completed steps 25 through 28.

25. If necessary, access your ArcGIS Image Server machine. Repeat steps 3 through 11 to create the folders and share them.
26. If necessary, follow the same process to share the arcgisserver folder with Everyone.
27. Open the ArcGIS Server Manager for your image server machine using an administrator account.
28. Repeat steps 14 through 24, replacing gisserver with the name of your image server.

    Tip:

    To optimize the performance of raster analysis on your system, you should set the number of instances on your server to match your number of cores. In ArcGIS Server Manager, click Services > System > Raster Processing. Under Pooling, set Maximum number of instances per machine to the number of cores available to you.

    Now that you have created folders to store the data for this tutorial and registered them with ArcGIS Server manager, you'll ensure that your servers are federated with your Portal.

Federate an ArcGIS Server site

An ArcGIS Server site licensed as an image server must be federated with your Portal to complete the configuration. Once a federated server is visible in your portal, you can assign it as a hosting server, raster analysis server, or other server type. This is essential for performing distributed raster analysis using ArcGIS Pro later in this tutorial.

1. Sign in to your Enterprise Portal as an administrator.

   Note:

   Your ArcGIS Enterprise Portal can be found at https://webadaptorhost.domain.com/webadaptorname/home. The webadaptorname is most commonly defined as portal.

2. On the ribbon, click the Organization tab and click the Settings tab.

   

3. On the side panel, click Servers.

   

   The Servers pane appears.

4. In the Servers pane, under Federated server sites, click Add server site.

   The Add server site window appears

   

   You'll federate your ArcGIS Image Server to your Portal using this window.

5. For Services URL, enter the URL to your image server.

   This should be the fully qualified domain URL used by external users when accessing the ArcGIS Server site.

   Tip:

   If the site has an ArcGIS Web Adaptor (IIS) configured, the URL will be formatted as http://gisserver.domain.com/webadaptorname

   Otherwise, the URL will be formatted as https://gisserver.domain.com:6443/arcgis (this is the same as the URL used in the next step).

6. For Administration URL, enter the URL used to access ArcGIS Server when performing administrative operations on the internal network.

   This URL will be formatted as https://gisserver.domain.com:6443/arcgis.

7. For Username, enter the name of the primary site administrator account that was used to initially log in to ArcGIS Server Manager and administer ArcGIS Server.
8. For Password, enter the password of the primary site administrator account.

   

9. Click Next.

   After a few minutes, the server is federated, or linked to your Enterprise account. Next, you’ll set it as the Raster Analysis Server in the Configure server role tab.

10. Scroll down to Raster Analysis Server and use the toggle button to enable raster analysis on the server.

    

11. Click Save.

    The federated server settings are saved.

    Your ArcGIS Server for performing raster analytics can now be accessed through your Enterprise. However, no one has access to it yet, aside from administrators. In the next section, you'll create a role that allows other users to leverage the analytical capabilities of your ArcGIS Image Server.

Assign permissions to perform raster analysis

To allow others to perform raster analysis, you'll need to create or edit a role to have the appropriate permissions to use the ArcGIS Image Server. If the rest of the tutorial is going to be completed by yourself or someone else with an administrator role, they already have the correct permissions and can move on to the next module.

If you would like another member of your organization to complete the tutorial who is not an administrator, you'll need to complete the steps below to edit or create a custom role for performing raster analysis.

1. On the side panel, click Member roles.

   

   This pane allows you to create new roles or edit existing roles.

2. Click Create Role.

   

3. For Role name, type Raster Analyst. For Description, type Role with privileges to perform raster analysis.

   

4. Under Role privileges, under General privileges, ensure that the following privileges are enabled as a minimum using the toggle button:

   Category	Privileges
   Members	View
   Content	Create, update, and delete Publish hosted feature layers Publish hosted dynamic imagery layers Publish server-based layers
   Sharing	Share with groups Share with portal Share with public
   Content and Analysis	Standard Feature Analysis Imagery Analysis

5. Click Save.

   Next, you'll assign the Raster Analyst role to your colleague so they can complete the tutorial.

6. Near the top of the page, click the Members tab.

   

7. Find the organization's member who is to complete the tutorial. Under Role, click the menu and choose Raster Analyst.

   

   This member now has all of the permissions that you assigned to the Raster Analyst role. Now, this user can leverage distributed raster analytics through ArcGIS Server while using ArcGIS Pro and Enterprise's Map Viewer Classic.

In this module, you reviewed the prerequisites for performing raster analysis with ArcGIS Image Server. Then, you added data stores, federated an ArcGIS Server site, and assigned the appropriate permissions to perform raster analysis. You are now ready to use your image server for raster analysis. In the next module, you will use distributed raster analysis to create a landslide risk map.

Create a landslide risk map

Image and raster data analysis provides valuable information for decision support in emergency management applications. Imagery can represent current information about a location and situation, and can be analyzed alongside historical imagery and other spatial information. Processing raster data is challenging because files are often large and complex. Additionally, data from different organizations and sources often needs to be shared and analyzed across the enterprise. The elastic distributed processing design of Raster Analytics provides an effective way to share and process large amounts of raster data quickly to support time-critical applications. Once optimized, you can save your processing chain, share it with members of your organization, and execute processing in your Raster Analytics deployment from ArcGIS Pro or the ArcGIS Enterprise's Map Viewer Classic.

In the previous module, you configured ArcGIS Enterprise for distributed raster analysis. In this module, you’ll create a landslide risk map and summarize the landslide risk based on watershed subbasin. You'll use raster function chains to derive a burn severity map, topographic slope map, and a land-cover index map. These individual processing chains will be combined into one processing chain for distributed processing in your Raster Analytics system and then be summarized by watershed subbasin.

Note:

This tutorial uses Map Viewer Classic. Map Viewer Classic is the predecessor of Map Viewer. Some functionality is not yet available in Map Viewer. It is recommended that you use Map Viewer Classic for the following workflow until it is supported in a future release of Map Viewer.

Set the active portal

First, you’ll need to set the active portal in ArcGIS Pro. This configuration step shares your account's licensing information with ArcGIS Pro and allows you to share processed data to your ArcGIS Enterprise for sharing.

1. Open ArcGIS Pro. Click Settings.

   

2. Click Portals.

   

3. If your portal is not listed, click Add Portal and enter your portal URL.

   

   Once detected, the portal is added to the list.

4. Right-click your portal and choose Sign in.

   When you sign in, make sure you use an account that has the correct permissions to use the raster analysis functionality.

5. Enter your username and password and click Sign in.
6. Right-click the portal and choose Set as Active Portal.

   A green check mark appears next to your portal connection.

   

7. Click the back arrow.

   

   Now that you're connected to your Portal, you'll open a project template to begin your analysis.

8. Click Start with another template.

   

9. Browse to C:\LandslideData on your Enterprise machine. Choose the project template file, Landslide_Risk_Project.aptx and click OK.

   

   Tip:

   If you can't locate this file, you can download and unzip LandslideData.zip to your local machine.

10. In the Create a New Project window, name your project Landslide_Risk and save it to your computer. Click OK

    

    The new project opens with a map centered on Santa Rosa, California.

    

Create a burn severity map

Different types of vegetation and materials burn with different intensity depending on their composition, density, topography, wind, soil moisture, and other factors. Generally, higher burn intensities result in higher water repellence and higher potential for erosion from a rainfall event. Burn intensity, or severity, can be derived from multispectral imagery with a near-infrared and shortwave infrared band, such as Landsat 8 imagery. Using raster functions in a processing chain, you’ll compute a burn ratio using Landsat 8 imagery acquired before and after the wildfires that took place around Santa Rosa, California in 2017.

To get started you'll add Landsat 8 imagery from before and after the fire, a digital elevation model, and landcover raster datasets.

1. On the ribbon, click the Insert tab. In the Project group, click Add Folder.

   

2. Browse to the LandslideData folder on drive C of your Enterprise machine. Select it, and click OK.

   

3. On the ribbon, click the View tab. In the Windows group, choose Catalog Pane.

   

   The Catalog pane appears.

4. In the Catalog pane, on the Project tab, expand Folders, and expand the LandslideData folder. Select all of the datasets inside except for Basins.tif and drag them onto the map.

   Tip:

   You can select multiple items at the same time by pressing the Ctrl key and clicking on the files.

   

   The data is now listed in the Contents pane. This includes Landsat 8 imagery for before (Before_L8.tif) and after (After_L8.tif) the October 2017 wildfires in Napa and Sonoma counties. There are also two layers you'll use as inputs for your risk map. The DEM_30m.tif layer is a digital elevation model showing the terrain's elevation. The Sonoma_NLCD2011.tif layer is a portion of the National Landcover Dataset, which shows land use and predominant vegetation type.

5. In the Contents pane, drag the After_L8.tif layer to the top of the list, and drag Before_L8.tif just below it. Turn off and collapse the Sonoma_NLCD2011.tif and DEM_30m.tif layers.

   

   Currently, the Landsat imagery is displayed in the map using the red, green, and blue bands. To compare the burn scars, you’ll display some of the imagery's multispectral bands.

   

6. Under After_L8.tif, right-click the red color chip and choose srband5.

   

7. For green, choose srband4, and for blue, choose srband3.

   

   This band combination displays the Landsat 8 imagery bands in color infrared mode. Vegetation is shown in bright red. Nonvegetated features such as bare and urban areas are displayed in various shades of gray and blue.

   

8. For the Before_L8.tif layer, set the following:

   • Change the red color chip to srband5.
   • Change the green color chip to srband4.
   • Change the blue color chip to srband3.

   

   Next, you'll use the Swipe tool, to compare the before and after imagery of the wildfire.

9. Click After_L8.tif in the Contents pane to select it.

   

10. On the ribbon, click the Raster Layer tab. In the Compare group, click the Swipe tool.

    

    The pointer displays as an arrow in the map display.

11. Click while swiping across the image in the map to compare the imagery before and after the wildfire.

    

    You can swipe vertically or horizontally. Notice that many areas that are red in Before_L8.tif are gray or green in After_L8.tif, indicating lost vegetation.

12. On the ribbon, click the Map tab. In the Navigate group, click Explore.

    

    The pointer returns to normal. Now that all the data is on the map, you’ll use raster functions to calculate the burn severity.

13. On the ribbon, click the Imagery tab. In the Analysis group, choose Raster Functions.

    

    The Raster Functions pane appears. On the System tab are categories of functions available for raster analysis. For this tutorial, two raster function templates, or RFTs, have been created for you. These custom function templates are listed under the Project tab.

14. In the Raster Functions pane, click the Project tab.

    

15. Right-click Landcover_Remap, point to Move to, then point to Custom and click Custom1.

    

    By moving these functions to a custom category, any edits you make to the RFTs will be saved if they are saved in the Function Editor. Changes made in the Project category will be lost if the project is not saved.

16. Click the Project tab. Right-click Burn_Severity and move it to Custom1.

    Next, you'll open and explore the Burn_Severity RFT.

17. In the Custom tab, right-click the Burn_Severity template and choose Edit.

    

    The Function Editor opens and displays the processing chain.

    

    The Band Arithmetic functions turn the pixels of the imagery into expressions. The postfire imagery is subtracted from the prefire imagery and run through a remap function. The remap function categorizes the pixel values into five categories of burn severity. The breakpoints of the five burn severity values are obtained from a landscape assessment study (Key and Benson, 2005). The Attribute Table function in the processing chain assigns a color ramp to the burn severity map. This has already been created for you.

18. Close the Burn Severity RFT in the Function Editor pane.

    

    Now that you understand how this raster function works, you'll use it to calculate the burn severity of the project area.

19. In the Raster Functions pane, click the Burn_Severity template.

    The Burn_Severity Properties raster function appears.

20. For Pre-Fire Imagery, choose Before_L8.tif, and for Post-Fire Imagery, choose After_L8.tif.
21. Make sure Output Layer Type is set to Raster Layer and click Create new layer.

    

    The processing may take a few minutes to complete. When finished, the resulting layer is displayed in the map and listed in the Contents pane. Raster functions are temporary in nature—calculations are performed on the fly, or in real time as you move on the map, and are not saved automatically. Burn severity is computed dynamically in the display as you navigate around the layer.

    

22. On the Quick Access Toolbar, click the Save button.

    

    Now that you've seen what a raster function can do, you'll learn how to build a raster function template in the next section to create a slope index map.

Create a slope index map

The slope map is a critical layer in determining slope stability. Slope steepness is derived from a digital elevation model (DEM). The steeper the slope, the more prone it is to slipping, especially during rainfall after stabilizing vegetation has been burned away. Next, you’ll build and save a raster function template to calculate percent slope and use it to create a steepness index.

1. On the ribbon, click the Imagery tab. In the Analysis group, click Function Editor.

   

   The Function Editor pane docks at the bottom of the map window.

2. In the Raster Functions pane, click the System tab. Expand the Surface group.

   

3. Drag the Slope function into the Function Editor pane.

   

4. In the Function Editor pane, on the ribbon, click Add Raster Variable.

   

   A green box titled Raster is added to the Function Editor pane.

   

5. Select the Raster box and position it to the left of the Slope function box.

   

   The Raster box will define the input dataset for the Slope function.

6. Point to the Raster box to see the Out parameter displayed. Click Out and drag to connect the raster element (Out parameter) to the Slope function (DEM parameter).

   

7. Right-click Raster and click Rename. Type Input DEM and press Enter.

   

8. Double-click the Slope function. In the Slope Properties window, click the Variables tab. For DEM, check the IsPublic field.

   

   The IsPublic option allows you to alter the input data in a later tool process.

9. Click OK.

   Your raster function will take an input digital elevation model and calculate its slope. The next function, Remap, will classify the slope into 5 categories of steepness.

10. In the Raster Functions pane, on the System tab, search for Remap.

    

11. Drag the Remap function into the Function Editor pane to the right of the Slope function.

    

12. Connect Slope to Remap by setting the Out of Slope to the Raster input for Remap.

    

    Next, you’ll set the inputs for the remap to index the slopes (in units of degrees) into five categories.

13. Double-click the Remap function. In the Remap Properties window, click the first box under the Minimum heading and type 0. For Maximum, type 5, and for Output, type 1.

    

14. Set additional categories with the following values:

    	Minimum	Maximum	Output
    2	5	15	2
    3	15	25	3
    4	25	35	4
    5	35	91	5

    

15. Click the General tab. For the Output Pixel Type, in the drop-down menu choose 8 Bit Signed.

    

    The Attribute table tool, which will be the next tool you add, can only take input rasters that are 8 bit. Hence, you set the Output pixel Type to 8 Bit Signed.

16. Click OK.
17. Right-click the Remap function and choose Rename. Type Slope Remap and press Enter.

    This will help distinguish between functions later in this tutorial when you string several raster function chains together.

18. In the Raster Functions pane, search for the Attribute Table function and drag it into the Function Editor pane to the right of Slope Remap.

    

19. Connect the output from the Remap function to the input of the Attribute Table function.

    

20. Double-click the Attribute Table function and set Table Type to Manual.

    

21. Under the blank table, click the Generate button.

    

22. For Maximum Value, choose 5. Click OK.

    Five rows are added with values 1 to 5 and a default green-to-red color scheme.

    

23. Click Class Name for each row and assign the slope classes as follows:

    Value	Class Name
    1	Flat
    2	Low
    3	Moderate
    4	Steep
    5	Very Steep

    

24. Click OK.

    Now that your raster function template is complete, you'll save it.

25. In the Function Editor pane, click Save As.

    

    The Save As window appears.

26. In the Save As window, for Name, type Slope_Index.
27. Make sure Category is set to Custom and Sub-Category is set to Custom1.
28. For Description, type A raster function template to derive slope from an input DEM.

    

29. Click OK.

    Your Slope_Index raster function template (RFT) now appears in the Custom category in the Raster Functions pane.

    

    Tip:

    You may need to clear the search bar before you can see the RFT.

30. In the Raster Functions pane, click Slope_Index.

    

31. For Input DEM, choose DEM_30m.tif. Make sure Output Layer Type is set to Raster Layer.

    

32. Click Create new layer.

    When it is finished processing, the layer displays on the map and is listed in the Contents pane with the name Slope_Index_DEM_30m.tif.

    

33. Close the Slope_Index RFT in the Function Editor pane and save your project.

    Now that you have a function to classify slope, you'll combine a number of RFTs together to create a landslide risk map.

Create the landslide risk map

The landslide risk calculation combines the two variables you just worked with: burn severity and slope. It also includes land-cover, which is also important to landslide risk. Vegetation stabilizes slopes via root systems. Wildfire can wipe out much of the stabilizing vegetation. Some types of vegetation, especially species of chaparral, have adapted to wildfire, and the root systems are especially deep underground to survive fires. Land-cover has already been indexed into five categories for you depending on its stabilizing effect on slopes. To perform the landslide risk calculation, you’ll add the three raster function templates into a chain that will be processed on your ArcGIS Enterprise deployment.

1. On the ribbon, on the Imagery tab, click Function Editor.

   The Function Editor pane appears.

2. In the Raster Functions pane, press the Ctrl key and select the Landcover_Remap, Burn_Severity, and Slope_Index RFTs. Drag them into the Function Editor pane.

   

   By default, the RFTs cluster together. You’ll want to separate them so that you can more easily connect their outputs.

   

3. Click and hold to draw a box around the Slope_Index functions, and then drag the entire group so that it’s below the Burn_Severity RFT.

   

   Tip:

   The green input boxes mark the beginning of each function chain. The Slope_Index RFT starts with the green Input DEM box.

   

4. Drag the Landcover_Remap RFT below Slope_Index RFT.

   

5. Right-click each Attribute Table function and rename it to match the corresponding Remap function.

   Their new names should be Burn Severity Attribute Table, Slope Attribute Table, and Landcover Attribute Table.

   

6. In the Raster Functions pane, click the System tab and search for the Weighted Overlay function. Drag it into the Function Editor pane to the right of the other three RFTs.

   

7. Connect the three Attribute Table outputs to the input parameter of the Weighted Overlay function.

   

8. In the Function Editor pane, click the Auto Layout button.

   

   The RFTs are arranged compactly.

   

9. Double-click the Weighted Overlay function.

   The Weighted Overlay Properties window appears. Inside the Weighted Overlay Table you can assign weights in percentages to each raster.

10. In the Weighted Overlay Table, in the cell next to <Burn Severity Attribute Table.OutputRaster>, type 30. For the <Slope Remap Attribute Table.OutputRaster> layer, assign 55 percent. For the <Landcover Remap Attribute Table.OutputRaster> layer, assign 15 percent.

    

    These hazard weights are loosely based on research done by the USGS for its National Landslide Hazards Program.

    The Remap Table is still empty. Since all three layers have the same number of index categories, you'll map each of them one-to-one.

11. In the Weighted Overlay Table, click the <Burn Severity Attribute Table.OutputRaster> layer. In the Remap Table, under Value, click NODATA to edit the attribute field and type 1. Under Scale, click NODATA and choose 1.

    

12. In the Remap Table, double-click the empty row at the bottom of the Value column and type 2. For Scale, choose 2.

    

13. Repeat the previous step to add rows 1 through 5 for all three rasters in the Weighted Overlay Table.

    

14. Click OK.
15. In the Raster Functions pane, on the System tab, search for the Attribute Table function and drag it into the Function Editor pane to the right of the Weighted Overlay function.

    

16. Connect the output from the Weighted Overlay function to the input of the Attribute Table function.
17. Double-click the Attribute Table function. In the Attribute Table Properties window, for Table Type, choose Manual.
18. Under the blank table, click the Generate button and set Maximum Value to 5. Click OK.

    Five rows are added with values 1 through 5 and a default green to red color scheme.

19. Click Class Name for each row and assign them the values as following:

    Value	Class Name
    1	Low
    2	Medium
    3	High
    4	Very High
    5	Extreme

    

20. Click OK to close the Attribute Table Properties window.
21. In the Function Editor, click Save As.
22. In the Save As window, for Name, type Landslide_Risk. Make sure Category is set to Custom and Sub-Category is set to Custom1.
23. For Description, type Raster Function Template to calculate landslide risk based on wildfire burn severity, slope, and landcover.

    

24. Click OK and close the Function Editor pane.

    Your raster function is complete. You'll now run it using distributed raster analytics.

25. In the Raster Functions pane, clear your search.

    

26. If necessary, click the Custom tab. Click Landslide_Risk.

    The Landslide_Risk raster function appears.

27. Fill in the input parameters as follows:

    • For Pre-Fire Imagery, choose Before_L8.tif.
    • For Post-Fire Imagery, choose After_L8.tif.
    • For Slope Input DEM, choose DEM_30m.tif.
    • For Landcover Remap Raster, choose Sonoma_NLCD2011.tif.

    

28. For Output Layer Type, choose Web Imagery Layer and click Next.

    

    Note:

    If you don't see an option to set your output to a Web Imagery Layer, talk to your administrator to make sure that the Raster Analysis server is set up properly and operational.

    The Output Generation pane appears and allows you to set the properties for the web layer you’ll create in your Enterprise.

29. For Name, type Landslide_Risk. For Description, type This web layer shows a landslide risk estimate for Sonoma County, CA.

    

30. For Tags, type Sonoma County, landslide, risk, wildfire. Press Enter.

    Four separate tags are added.

    

31. Click Run.

    The processing chain is submitted to your Enterprise deployment for distributed processing. A message appears, informing you that the process was submitted.

    

32. Click the Raster Functions notification to view the status of your RFT.

    The History pane appears and the Raster Functions tab is selected. Any raster functions that you have previously used will be listed here.

    Note:

    If the Raster Functions notification disappeared, there is another method to access the status of your raster processing. On the ribbon, click the Analysis tab. In the Geoprocessing group, click History. In the History pane, click the Raster Functions tab.

    

    You'll see a green tick next to the raster function once the process has successfully completed. You'll analyze this layer later using the Map Viewer Classic.

Summarize landslide risk by subbasin

Although the landslide risk map is useful, you want to go further to break down the areas that are most at risk. Because landslide risk is impacted by precipitation patterns and watershed characteristics, you'll summarize risk by watershed basins within the study area. First, you’ll publish the watershed basin layer to your Portal. Then, you’ll use the landslide risk dataset produced in the previous section to summarize risk per subbasin.

1. In the Catalog pane, click the Project tab and browse to the LandslideData folder connection.
2. Right-click Basins.tif and choose Share as Web Layer.

   

   The Share As Web Layer pane appears. This pane allows you to name and configure this raster dataset when you publish it to your Portal.

3. Under Item Details, set the following:

   • For Name, type Basins.
   • For Summary, type Watershed subbasins in Napa and Sonoma counties, California.
   • For Tags, type watershed, basin, California and press Enter.

   

   Next, you'll ensure that this raster dataset is referenced from the LandslideData folder and not saved as a copy to the Portal.

4. Under Layer and Data Type, make sure Reference registered data is selected.

   

5. Under Location, for Server and Folder, choose your Hosting Server.

   

6. Click Analyze, and if there are no warnings, click Publish.

   Note:

   If a warning is shown that the data source is not registered, talk to your administrator to ensure the LandslideData folder datastore is configured properly.

   When the web layer succeeds, a success note is shown in the pane.

7. Save your project.
8. Click the Manage the web layer link.

   

   The item details page for your Basins layer appears.

   

9. Click the browse button next to the Basins layer and choose Open in Map Viewer Classic.

   

   The Map Viewer Classic opens.

   

   Next, you'll add the Landslide_Risk dataset to the map.

10. On the ribbon, click Add and choose Search for Layers.

    

11. Confirm that the search is set to My Content. Find your Landslide_Risk layer, and click the Add button.

    

    The Landslide_Risk layer is added to the map.

    Note:

    If the landslide risk layer fails to load in the map, you may need to wait a few minutes for processing to complete and try again.

    Now that you have a layer for basins and for risk, you'll calculate the average risk per basin with the Summarize Raster Within tool.

12. On the ribbon, click Analysis and choose Raster Analysis.

    

13. Expand Summarize Data, and click the Summarize Raster Within tool.

    

14. For the Summarize Raster Within tool, fill out the following parameters:

    • For Choose area layer to summarize a raster layer within defined boundaries, choose Basins.
    • For Choose field to define the boundaries, choose Value.
    • For Choose raster layer to summarize, choose Landslide_Risk.
    • For Choose statistic to calculate, choose Average.
    • For Ignore missing values in calculation, check the box next to Ignore.
    • For Process as multidimensional, uncheck the box next to All slices.
    • For Result layer name, type Risk per Basin.
    • Uncheck the box next to Use current map extent.

    

15. Click Run Analysis.

    When the analysis finishes, a dataset that shows the average risk per watershed is added to the map.

    

    The areas in white and light gray have higher landslide risk values. This is based on the risk you calculated using the raster function template with the weighted inputs of slope, burn severity, and land-cover. However, the current results are difficult to see with this symbology. After you save the map, you'll update the symbology. This will make it easier to understand the results from your analysis.

16. On the ribbon, click Save and choose Save As.

    

    The Save Map window appears.

17. In the Save Map window, set the following:

    • For Title, type Landslide Risk per Basin (Sonoma and Napa).
    • For Tags, type landslide, risk, wildfire and press Enter.
    • For Summary, type Landslide risk per basin in Sonoma and Napa counties, based on wildfire burn severity, slope, and landcover.

    

18. Click Save Map.

You used raster function chains to create a burn severity map, slope index map, and land-cover index map. You then created a landslide risk map, published layers to the Portal, and summarized risk by watershed subbasin. Next, you’ll communicate your findings to other members of your emergency response organization by creating a web app to share the results across your Enterprise.

Share a web app

In the previous module, you created a risk map that summarized landslide risk per subbasin. Now, you want to communicate the results with the rest of your organization, which includes emergency response personnel in the office and on the ground. To share your results, you’ll create a web app in your Portal.

Prepare your map

Now that you've completed your analysis, you're ready to make your map more presentable for your intended audience. For this, you'll use the Map Viewer.

1. If necessary, open your ArcGIS Enterprise Portal in your web browser and sign in. Browse to the Landslide Risk per Basin (Sonoma and Napa) map you created in the previous module.
2. Click Open in Map Viewer.

   

   Next, you'll remove some layers from the map.

3. In the Layers pane, for Basins, click Options. Choose Remove.

   

4. Remove the Landslide_Risk layer.

   When you switched to the Map Viewer, underscores were added to the name of the Risk_per_Basin layer. You'll remove the underscores.

5. For Risk_per_Basin, click Options. Choose Rename. For Title, type Risk per Basin. Click OK.

   

   Next, you'll update the layer's symbology.

6. In the Layers pane, select the Risk per Basin layer.
7. On the Settings (light) toolbar, click Styles. Under Select Style, ensure that Stretch is selected and click Style Options.

   

8. For Stretch Type, choose Percent Clip.

   

9. Under Color scheme, click the Edit button. In the Color scheme window, click the Edit button.

   

   The Ramp window appears. You'll choose a green-to-red color ramp where the areas of greater risk are red and the lower risk areas are green.

10. In the Ramp window, choose the green-to-red color ramp named Slope.

    Tip:

    Point to a color ramp to see its name.

    

    The colors are reversed. Currently, areas in red are those that have a lower risk value. You'll fix this next.

11. Click Flip ramp colors and in the Style options pane, click Done.

    

12. Now that the Risk per Basin layer has a more appropriate symbology, you'll apply a blend mode allowing your audience to see the layer containing risk values and the underlying basemap.
13. On the Settings (light) toolbar, click Properties.

    The Properties pane appears.

    

14. Under Appearance, under Blending, choose Multiply.

    

    With the Multiply blend mode, you are able to simultaneously observe the basemap with it's features and the colors that represent risk across the study area.

    

    Before you share your results, you'll update the map extent.

15. In the Layers pane, for the Risk per Basin layer, click Options. Choose Zoom to.

    The map centers on the Risk per Basin layer.

    

16. On the Contents (dark) toolbar, click Save and open. Choose Save.

    

    You're ready to share your map as an app for others to use.

Create a web app

Apps allow you to share your results with other users within your Enterprise. You'll be taking the map that you created and sharing it with ArcGIS Instant Apps. These apps can be configured in minutes. While there are many different templates to choose from, you'll build a Basic app in this tutorial. This app will function seamlessly on any desktop or mobile device.

1. On the Contents (dark) toolbar, click Create app. Choose Instant Apps.

   

   You'll be able to choose from a number of different templates.

   

2. Find the Basic template and click Choose.

   

   The Create app - Basic window appears. Before configuring your app, you'll provide a name and tags.

3. For Give your app a title, type Landslide Risk per Basin (Sonoma and Napa). If necessary, for Tags type landslide, risk, wildfire.

   

4. Click Create app.

   An app is generated and you are taken to a page where you can configure it further. The Express pane walks you through the steps of building an app and a preview of the final app is available to you.

   

   Note:

   If the Express window appears, you can close it. This window provides extra information about how to configure Instant Apps.

   You'll make a few adjustments to this app before you share it. Since your app already has a map, you'll start with Step 2. About.

5. In the Express pane, click Step 2. About.

   

   The About pane appears. You can add a title, a legend, and choose where pop-ups appear in the app.

6. In the About pane, use the toggle to turn on Header.

   

   A title appears at the top of the app. This is the same title as your map.

7. Click Next.

   

   The Interactivity pane allows you to configure how users interact with the app. Different widgets can be added or removed from your app to help users turn layers off and on, take a screenshot, or search for locations. You'll leave the defaults.

8. Click Next.

   The final step is the Theme & Layout pane. You can change the app's color scheme and move the widgets to different locations within the app. You'll update the app's theme.

9. In the Theme & Layout pane, under Select a mode, choose Dark.

   

   The banner and widget icons turn dark gray. Next, you'll publish your app.

10. Click Publish. In the Publish window, click Confirm.

    

    After a few seconds, the publishing is complete. Before you share an app with others, you should always test it first.

11. In the Share window, click Launch.

    

    The app opens in a browser tab. Explore your app and test it.

    

    Your app is complete. Next, you'll share it with your organization. You'll switch back to the browser tab where you configured the app in previous steps.

12. In your browser, click the ArcGIS Instant Apps Configuration tab.

    

    You are taken back to the app configuration page. Now, you'll share your app.

    Note:

    If you want to make any changes to your app, this can be done at any time. Be sure to republish your app after making changes.

13. In the Share window, click Change share settings.

    

    Note:

    If the Share window is not visible, on the Contents toolbar, click Share.

    Now, you have the ability to choose who has access to your app.

14. Under Set sharing level, choose Organization. Click Save.

    

    The Update sharing window appears. Since you want to share your app with your organization, this requires you to share your app's underlying web map and any datasets that the map contains with your organization as well. You'll update the sharing settings for the Landslide Risk per Basin (Sonoma and Napa) map and the Risk_per_basin imagery layer.

    

15. Click Update.

    The app and its underlying content have been shared. Next, you'll retrieve a link for your app that you can share with others for them to access the app.

16. On the Contents toolbar, click Share. Click Copy Link.

    

17. Open a new browser tab. Paste the link into the web address bar and press Enter.

    The app opens. You can share this link with others who need access to your app.

In this module, you created a web app to share your landslide risk map. By sharing the web app with your ArcGIS Enterprise, you ensured that all members of your organization, whether in the office or in the field, have access to this vital information for decision-making. The flexibility of sharing in ArcGIS Enterprise and customization using ArcGIS Instant Apps allows you to share the information you want with who you want.

Additionally, your ArcGIS Enterprise deployment is now configured to perform raster analyses. Using the distributed processing capabilities of raster analysis, you created a landslide risk map and summarized the results by watershed subbasin. The patterns that were revealed in your map helped you determine which subbasins were most at risk of landslides after the wildfires occurred. Finally, you created and shared a web app to communicate your findings to your entire organization and help other emergency response personnel gain valuable insight into the risk of landslides.

You can find more tutorials in the tutorial gallery.

Acknowledgements

• World Topographic Map sources: Esri, HERE, Garmin, FAO, NOAA, USGS, © OpenStreetMap contributors, and the GIS User Community.
• Digital Elevation Model (DEM) courtesy of U.S. Geological Survey, downloaded via TNM Download (v2.0).
• Landsat scenes (dated: 19/25/2017, 12/13/2017, 12/22/2017, and 12/23/2017) courtesy of U.S. Geological Survey, downloaded via USGS Earth Explorer.
• U.S. Geological Survey, 2014, National Land Cover Database (NLCD) 2011 Land Cover Conterminous United States: U.S. Geological Survey data release, https://doi.org/10.5066/P97S2IID.
• The basins dataset was derived from the Digital Elevation Model, courtesy of U.S. Geological Survey, and processed using the ArcGIS Spatial Analyst extension.