Identify landslide risk areas in Colorado

Historic rains pounded Colorado's Front Range for a week in September 2013, triggering floods and mudslides that killed 10 people and caused $2 billion in damage. In this lesson, you'll analyze Boulder County's flood- and mudslide-prone areas for vulnerable populations as part of an analysis seeking to minimize the loss of life and property should a similar disaster strike the region.

This lesson was last tested on April 18, 2024.

View final result

Requirements

• Publisher or Administrator role in an ArcGIS organization: ArcGIS Online (see options for software access) or ArcGIS Enterprise (learn more)
• 1 credits

Analyze flood risk

You'll first examine your study area in Boulder County, along with some layers depicting floodways, geologic hazards, and census blocks. After visually investigating their relationships for a better understanding of the region's unique geography, you'll buffer and enrich the Floodways layer to determine areas of high flood risk.

Sign in and explore the map

To investigate the data, you first need to open the map.

1. Open the Boulder County Geologic Hazard Zones web map.

   The map opens in Map Viewer.

   

   Next, you will sign into your ArcGIS account so you can save a copy of the map to your own account.

2. Sign in to your ArcGIS organizational account.

   Note:

   If you don't have an organizational account, see options for software access.

3. On the Contents (dark) toolbar, click Save and open and click Save as.

   

4. In the Save map window, for Title, type Boulder County Map and add your name or initials. For Summary, replace the existing text with Web map displaying areas of high flood and landslide risk.

   Note:

   You cannot create two layers in an ArcGIS organization with the same name. Adding your initials to a layer name ensures that other people in your organization can also complete this tutorial. Once a layer has been created, you can rename it in the map to remove your initials, which will not affect the name of the underlying data layer.

   

5. Click Save.

   You now have a copy of the map saved to your account's My Content page and the updated title is shown at the top of the map.

   The Legend pane is open and shows that the Geologic Hazard Zones layer has four classifications: Major Hazard, Moderate Hazard, Moderate Constraint, and Minor Constraint.

   These classifications represent the likelihood of major geotechnical problems—primarily landslide potential—determined by slope (steepness of terrain), aspect (direction of slope), and soil type. Most of the Major Hazard zone in is on the western side of the county, and a thin corridor of the zone extends up the central part of the county. There are also additional Major Hazard zones scattered in the southeast.

Filter the hazards layer

For your analysis, you will only use the Major Hazard classification. In this step, you'll filter the layer to display only this classification, making visual analysis easier.

1. In the Contents toolbar, click Layers.

   

2. In the Layers pane, for the Geologic Hazard Zones layer, click the Options button and click Show table.

   

   The table appears and shows the attributes of the layer. For this data, there is only one visible attribute: the Description field, which describes the type of hazard zone. You'll use this field to filter the layer.

   

3. Close the table.
4. In the Layers pane, if necessary, click the Geologic Hazard Zones layer to make it active.

   The blue line next to the layer name indicates that the layer is active.

   

5. In the Settings (light) toolbar, click Filter.

   

   The Filter pane appears, which allows you to create an expression that will limit the features a layer displays.

6. In the Filters pane, click Add expression.
7. For Expression, confirm that the first drop-down menu of the expression is set to Description, and set the value drop-down menu to Major Hazard.

   

   The expression is set to Description is Major Hazard, which means to show only features that are major hazards.

8. Click Save.

   The map updates, now with only the major hazards (in red) visible.

   

Investigate the census block points and floodways

While the geologic hazard data provides some insight into the landscape of Boulder County, it does not help you understand which areas are at risk in the event of a major flood or landslide. For that, you'll need to compare the high hazard zones to floodway and population layers.

1. In the Layers pane, for the Census Block Points layer, click the Visibility button.

   

   The Census Block Points layer is visible on the map.

   

   Each point indicates the centroid of a census block, a small geographic unit used by the United States Census Bureau to track population. Larger points indicate higher populations.

   Note:

   Learn more about United States census geography.

   A visual comparison of the census blocks to the geologic hazard zones brings some good news: the majority of the census blocks lie outside of the Major Hazard zones. You might assume this means most people (and property) will be safe when disaster strikes.

   Unfortunately, although landslides and other geologic hazards may begin in high geologic hazard zones, that's not necessarily where they end. Floods can carry mud and debris from the narrow canyons of the Rocky Mountains as far as a kilometer downstream and cause subsequent flooding upstream, impacting areas outside of the hazard zones.

   To expand your analysis to include the possibility of geologic hazard flow from one area to another, you'll examine the Floodways layer.

2. In the Layers pane, click the Visibility button for the Floodways layer to turn the layer on.

   The Floodways layer is visible on the map.

   

   A floodway is the channel of a stream and the areas adjoining the channel that carry floodwaters downstream. They comprise part of the flood plain, which is the area that may be underwater during a major flood event.

   The floodways flow from west to northeast, draining from the high elevation of the Rocky Mountains into the relatively low elevation of the eastern plains. Unlike the Geologic Hazard Zones layer, many of the floodways intersect large population centers. During a flood, large numbers of people may be at risk.

As previously explained, the floodways only comprise part of the flood plain. If you are to fully understand the risk involved in a flood event similar to the September 2013 flooding, you'll need to estimate the area that may be submerged during a flood.

Buffer the floodways and examine potential flood extent

Although the Federal Emergency Management Agency (FEMA) freely provides flood plain GIS data, for the instructional purposes of these tutorials, you'll instead create a buffer around the Floodways layer to estimate the flood plains. While not an exact approximation of flood activity, it'll give you an idea of the stakes involved during a natural disaster.

1. In the Settings toolbar, click the Analysis button.

   Note:

   If you do not see the Analysis button in Map Viewer, contact your ArcGIS administrator. You may not have the privileges required to perform analysis.

   Learn more about licensing requirements for spatial analysis.

   

2. In the Analysis pane, click Tools.
3. In the Tools pane, expand Use proximity and click the Create Buffers tool.

   

4. In the Create Buffers pane, for Input features, choose Floodways.
5. Under Buffer settings, for Distance values, type 200 and press Enter. For Units, choose Meters.

   

   Two hundred meters is an estimation of the flood fringe, or the area around a floodway that may become inundated with water during a major flood. The floodway and flood fringe combined make up the flood plain.

6. Under Result layer, for Output name, type Floodway Buffers and add your name or initials.

   Running analysis tools requires credits. Credits are the currency used across ArcGIS Online. They are consumed during specific transactions, such as performing analytics, storing features, and geocoding.

   Before running an analysis, you can use the Estimate credits button to check how many credits will be consumed. When running analysis tools, the credit cost is typically calculated by multiplying the number of features by the credit cost of the tool.

   Note:

   You can learn how many remaining credits are in your ArcGIS Online account if your organization administrator has allowed you to view that information. If it is enabled, at the top of the page, click your username and choose My settings. On the My settings page, click Credits to see how many remaining credits are in your account. If it is not enabled, contact your organizational account administrator.

7. Click Estimate credits.

   This analysis will consume 0.023 credits.

8. Click Run.

   When the analysis is complete, a new layer is added to your map.

   

   At this point, you no longer need the Floodways layer.

9. In the Layers pane, for the Floodways layer, click the Options button, and choose Remove.

   

   Next, you will update the layer name for the Floodway Buffers layer.

10. In the Layers pane, for the Floodway Buffers layer, click the Options button and choose Rename. Remove your name or initials and click OK.

    It is important to remember to periodically save your progress on your map, so you will save the map now.

11. On the Contents toolbar, click Save and open and click Save to save your map.

    Now that you have estimated the extent of flooding, you'll investigate a few places around Boulder County where flooding may pose a particular problem.

12. On the Contents toolbar, click Bookmarks. In the Bookmarks pane, choose City of Boulder.

    

    The map zooms into the city of Boulder.

    

    Boulder is the most populous city in Boulder County as well as the seat of the county government. Several estimated flood plains run through the city, with many census block points (and thus large numbers of people) at risk. The damage here during a major flood in both property and life could be catastrophic if authorities are not properly prepared.

13. Zoom to the Lyons bookmark.

    The map zooms into the city of Lyons.

    

    Lyons is a small town nestled in the Rocky Mountains where two floodway buffers converge. Compared to Boulder, few people live here. However, the floodway buffers cover all major roads into and out of the town, including the Ute Highway and the South St. Vrain Highway. While fewer people may be at risk in this area, those who are at risk may be potentially stranded if flooding renders the roads unusable.

14. Zoom to the Louisville bookmark.

    The map zooms into the city of Louisville.

    

    Louisville is a suburban community in southern Boulder County, near the Denver metropolitan area. A major floodway buffer runs along the southern fringe of the city. However, although many more people live in Louisville than in Lyons, a relatively small portion of that population lives in an area at risk of flooding. Furthermore, while some major roads are in danger of being blocked by floodwaters, the flood plain mostly runs through non-vital infrastructure, such as the Coal Creek Golf Course and the Dutch Creek Park. While it is an area that may be a flood risk, at the present moment, Louisville does not appear to be a particularly high-risk area.

15. Zoom to the Boulder County bookmark and save the map.

You've conducted a visual analysis of the population at risk during a flood, but visual analysis can only give you a rough idea of what is really happening. In the next section, you'll conduct a more precise analysis of the at-risk population.

Enrich the floodway buffers and display the data

You'll use the Enrich Layer tool on the Floodway Buffers layer to find an estimate of how many people live in potential danger of flooding. Then, you'll configure the layer's pop-up to better display the population data.

1. In the Create Buffers pane that is still open, click the back arrow.
2. Expand the Enrich data section and click the Enrich Layer tool.
3. In the Enrich Layer tool pane, for Features to enrich, choose Floodway Buffers.
4. Under Enrichment data, click the Variable button.

   

   The Data Browser appears. It is a directory of all of the attributes with which you can enrich your layer.

5. In the Data Browser category page, locate and click Population.

   

6. Under Choose a Popular Variable, check 2023 Total Population (Esri).

   

   Note:

   Data Browser information is updated periodically. Your variables and values may differ. Use the most updated data available.

7. At the top of the Data Browser page, confirm that only one variable has been selected. Click Select at the bottom of the window.
8. In the Enrich Layer pane, for Output name, type Enriched Floodway Buffers and add your name or initials.

   

9. Click Run.

   Note:

   Running this tool will require 0.23 credits.

   A new layer is added to your map. It looks like the original Floodway Buffers layer, but this new layer contains attribute information about population. You can find this information in the layer's table or the layer's default pop-up.

10. In the Layers pane, remove the Floodway Buffers and Census Block Points layers.
11. Rename Enriched Floodway Buffers to Floodway Buffers.

You've investigated the data on flood risk and mapped where and who is at risk in a flooding event using the Create Buffers and Enrich Layers tools.

Configure pop-ups

Next, you will configure the pop-ups for the Floodway Buffers layer so when your audience clicks on a floodway area, they will see the most important information related to the area.

1. Click one of the floodway buffers on the map to view its pop-up.

   

   The 2023 Total Population attribute is in the pop-up, but it's not displayed in the most intuitive way. The pop-up could also use some information explaining what the floodway buffer represents.

2. Close the pop-up.
3. In the Layers pane, ensure the Floodway Buffers layer is active, and on the Settings toolbar, click Pop-ups.
4. For the Title, delete the existing text and click the add field button.

   

5. In the Add Field pane, under the Fields list, click Name.

   The pop-up title will now display the name of the creek selected in the Floodway Buffer layer.

   Instead of showing the list of fields and their values, you want the pop-up to show a customized sentence that includes the total population data. First, you will remove Fields list.

6. In the Pop-ups pane, click the Options button for Fields list and choose Delete.

   

7. Click the Add content button and choose Text.

   The text editor appears

8. In the text editor, type A total of and type an open curly bracket, {.

   A list of fields appear. The open curly bracket indicates you want to include dynamic text based on one of the fields in the layer.

   

9. In the list of fields, click 2023 Total Population.

   The field name for the 2023 Total Population field adds to the text.

   

10. At the end of the existing text, type people live in this 200 meter floodway buffer meant to estimate the area underwater during a major flood event.
11. Highlight the {TOTPOP_CY} text and click the Bold button.
12. Click OK.

    The pop-up updates.

    

    Next, you want to configure the format of the 2023 Total Population field so that it doesn't have any decimal places.

13. In the Settings toolbar, click Fields.
14. In the Fields pane, click the 2023 Total Population field.
15. In the Formatting window, for Significant digits, choose 0 Decimal places.

    

16. Click Done.

    The pop-up is configured.

17. Save the map.

Analyze landslide risk

Previously, you examined a map of Boulder County to better understand the spatial relationship between geologic hazards, floodways, and human population. You then mapped flood risk and enriched the data with population statistics. Next, you'll identify areas of landslide risk and investigate additional data variables, such as property value, that might be important to understand the total risk posed to an area.

Find floodplains that intersect geologic hazard zones

As you learned in the previous tutorial, floodplains can be dangerous simply for their flooding potential. However, the danger does not end there. When floodplains intersect areas of high geologic hazard, they can become corridors for conveying mud and debris in an event known as a landslide. To find where these landslides might occur, you'll first find floodplains that cross geologic hazard zones.

1. If necessary, open your Boulder County Map.
2. In the Settings toolbar, click the Analysis button.
3. In the Analysis pane, click Tools. Search for and open the Find by Attributes and Location tool.
4. In the Find by Attributes and Location tool pane, click the Build new query button.

   

   You'll need to build an expression to find floodway buffers that intersect hazard zones.

5. In theQuery builder window, click Spatial expression and click Next.
6. Ensure that Find features from is set to Floodway Buffers. Under Where, build the expression Intersects Geologic Hazard Zones.

   

   Based on this expression, the tool will create a layer that includes only floodplains that touch the geologic hazard zones. The operation only considers filtered features, so only Major Hazard zones will be used for the analysis.

7. Click Add.
8. In the Criteria section, check the Include only the parts of features that meet the criteria box.

   

9. In the Result layer section, for Output name, type Potential Landslide Risk Areas, add your name or initials.

   

10. Click Run.

    Note:

    Running this tool requires 0.064 credits.

    A new layer is added to the map, depicting only floodway buffers that intersect Major Hazard zones.

    

    While these floodway buffers have the potential of ferrying landslide debris downstream, it is unlikely that the entire length of the floodplain constitutes a landslide risk zone. Landslide debris can only travel so far along the relatively flat eastern plains before it comes to a stop.

11. Save the map.
12. In the Layer pane, click the Visibility button on and off for Floodway Buffers layer to better see the Potential Landslide Risk Areas layer.
13. Use Bookmarks to zoom to the City of Boulder bookmark.

    

    The new layer represents the floodplains that intersect zones classified as a major hazard. These are areas where rock and mud from the hazard zones may funnel into the floodplains and cause a landslide.

14. In the Bookmarks pane, click the Boulder County bookmark.
15. Check the box next to the Potential Landslide Risk Areas layer to turn it back on.

Derive landslide risk areas and explore the results

In this section, you'll derive new locations a certain distance from the Potential Landslide Risk Areas layer. These new locations will indicate areas potentially affected by a landslide—the landslide risk area.

1. If the Find by Attributes and Location tool pane is still open, click the back arrow and open the tool again so that all the previously entered parameters are cleared.
2. In the Find by Attribute and Location tool pane, click Build new query.

   As when you found the potential landslide risk areas earlier, you'll construct an expression to determine the areas you want.

3. In the Query builder window, for Find features from, choose Floodway Buffers. Choose Spatial expression and click Next.
4. Under Where, build the expression Within a distance of 1 Kilometers from Potential Landslide Risk Areas.

   

   One kilometer is the distance you'll use to estimate how far a landslide may travel within the floodways. Normally, the distance will be affected by the slope and terrain of the area over which the landslide travels, but one kilometer will suffice for the purposes of your analysis.

   This expression will derive a new layer that includes all locations in the Floodway Buffer layer within one kilometer of the Potential Landslide Risk Areas layer—in other words, all the areas one kilometer upstream and downstream of where a landslide enters a floodplain.

5. Click the Add button.
6. In the Find by Attribute and Location tool pane, for Output name, type Landslide Risk Areas and add your name or initials.

   Note:

   Running this tool requires 0.047 credits.

   A new layer is added to the map. The new layer depicts areas potentially affected by a landslide.

   

7. Rename the new layer and removing your name or initials.
8. Remove the Potential Landslide Risk Areas layer.

   Now that you've mapped the areas prone to landslide activity, you'll take some time to explore the map a little more closely to see how population and infrastructure may be affected by a landslide event.

9. If necessary, on the ribbon, click Bookmarks and click City of Boulder.

   As with flood risk, the number of people in danger of landslides is relatively high in Boulder, because it is a major population center at a confluence of many floodways and geologic hazard zones. The landslide risk here is primarily downstream, meaning that people and property are under threat of being buried by landslide debris itself.

   

10. Zoom to the Lyons bookmark.

    Only one relatively small landslide risk area threatens Lyons. However, unlike Boulder, the landslide threat here is primarily upstream rather than downstream. The people and property of Lyons aren't in danger of being buried under landslide debris as much as they are in danger of the extreme upstream flooding that might occur if a landslide dams up a floodplain. A landslide event in Lyons may exacerbate the already-severe flooding and compound problems for the people of Lyons.

    

11. Zoom to the Louisville bookmark.

    Only one landslide risk area travels through Louisville, but it is by far the largest risk area in Boulder County, due to the presence of multiple scattered geologic hazard zones throughout the city. As you discovered before, relatively few people in Louisville live in the southern fringe of the city where flooding and landslides are most likely to take place. However, the sheer size of the landslide risk area in Louisville may pose a particular difficulty for disaster preparations.

    

12. Zoom to the Boulder County bookmark and save the map.

Visual analysis only tells part of the story. You'll need to find more exact statistical data on the landslide risk areas to learn the whole of it.

Enrich the landslide risk areas

Next, you'll enrich the Landslide Risk Areas layer with population data to gain an even more complete picture of who and what is at risk during a landslide.

1. In the Analysis pane, search for and open the Enrich Layer tool.
2. In the Enrich Layer pane, for Input features, choose Landslide Risk Areas.
3. Under Enrichment data, click Variable.

   

   The Data Browser window appears.

4. In the search bar at the top of the Data Browser window, type 2023 total population and press Enter. Check the box next to 2023 Key Demographic Indicators (Esri).

   

   Tip:

   Demographic data in the Data Browser window is periodically updated. Use the most recent available data.

   The 2023 Key Demographic Indicators (Esri) group contains the 2023 Total Population field. By checking the 2023 Key Demographic Indicators (Esri) box, you have added 2023 Total Population to your list of selected variables.

5. Click the category button in the Data Browser window to return to the main menu.

   

6. In the search bar, type total housing units and press Enter.
7. Expand 2023 Housing Unit Time Series (Esri) and check the box next to 2022 Total Housing Units (Esri 2023).

   This statistic will indicate at-risk property.

8. Click the category button. In the search box, type average household income and press Enter. Check the box next to 2023 Income (Esri).

   This statistic will give you insight into the characteristics of the population at risk.

9. Click the category button. In the search box, type seniors and press Enter. Expand 2023 Age Dependency (Esri) and check the box for 2023 Seniors (Age 65+) (Esri).

   

   This statistic will inform you of the number of elderly people who live in an area, who may require special assistance in preparing for a flood event.

10. Click Select.

    The four variables you selected are added to the Enrich Layers tool pane.

    

11. In the Enrich Layer tool pane, for Output name, type Enriched Landslide Risk Areas and add your name or initials and click Run.

    Note:

    Running this tool will require 0.48 credits.

    The new layer adds to the Layers pane. Next, you will add data on road density.

12. In the Enrich Layer tool pane that is still open, for Input features, choose the Enriched Landslide Risk Areas layer.
13. Under Enrichment data, click the Variable button.

    The Data Browser window appears.

14. In the Data Browser window, under Variables, in the bottom drop-down menu, choose Landscape.

    

15. Click the Landscape category.

    

16. In the search bar, type road density and press Enter. Check the Relative Road Density (Km) box.

    

    This statistic indicates the average total road length in an area per square kilometer, which will reveal the potential danger to road infrastructure in the landslide risk areas.

17. Click Select.
18. In the Enrich Layer tool pane, for Output name, type Enriched Landslide Risk Areas Landscape and add your name or initials, and click Run.

    Note:

    Running this tool will require 0.12 credits.

    The new layer is added to the map.

    Although the original Landslide Risk Areas, Enriched Landslide Risk Areas, and Enriched Landslide Risk Areas Landscape layers appear the same on the map, the enriched layers contain additional demographic and landscape attribute information. You can view this information in the layer's table or the layer's default pop-up.

19. Remove the Landslide Risk Areas and Enriched Landslide Risk Areas layers from the map.
20. Rename the Enriched Landslide Risk Areas Landscape layer to Landslide Risk Areas.

    

21. Save the map.

You've mapped both areas of flood risk and areas of landslide risk, with relevant demographic and infrastructure data. Now all you have left to do is symbolize the Landslide Risk Areas layer and configure its pop-up to more clearly relate the information to the viewer.

Symbolize the landslide risk areas

Maps aren't just about proper analysis and spatial data. You also need to be able to communicate your results to an audience. In the final section, you'll change the visual aspects of the Landslide Risk Areas layer to better convey the danger involved by using a custom icon to denote landslide risk.

1. In the Layers pane, ensure the Landslide Risk Areas layer is active, and in the Settings toolbar, click Styles.
2. In the Styles pane, under Choose attributes, click the Field button.

   

3. In the Select fields window, check the box for Buffer distance in Meters.

   

4. Click Add.

   Buffer distance in Meters measures the size of the buffer for each feature in the Landslide Risk Areas layer. You could use any field to symbolize the layer, but this field is convenient because it only contains one value—200, the size you set your buffer distance to be in the previous tutorial. This results in one symbol type.

   Normally, only point features can be symbolized with an icon. However, you can symbolize polygon features as if they were point features by using a graduated classification scheme such as size or color.

5. Click Counts and Amounts (size) and click Style options.

   

6. In the Style options pane, scroll below the histogram and click the symbol under Background symbol style.

   

   The Background symbol style window appears. You can use this window to change the background of your symbol's icon.

7. For Fill color, choose a bright yellow color, like ffff3f.

   

8. For Outline color, choose black. For Outline transparency, type 50. For Outline width, type 2.

   

9. Close the Background symbol style window.
10. In the Style options pane, click the symbol under Symbol style.

    

    The Symbol style window appears, allowing you to change the graduated circles symbol (as opposed to the symbol for the polygon features). Instead of using a default symbol, you'll add a custom symbol.

11. In the Symbol style window, click Basic point.
12. In the Change symbol pane, for Category, choose Uploaded Symbols.

    

13. Download the landslide icon image. Save the image to a location on your computer that you can easily locate, like the Desktop or Downloads folder.

    The URL takes you to a symbol specifically designed to communicate landslide risk.

14. Drag the image or click Browse to add the downloaded image to the Change symbol window.

    The landslide icon adds to your list of uploaded symbols.

15. Select the landslide icon and click Done.

    The default size of 12 pixels appears small on the map. You are unable to adjust the size of the symbol in the Symbol style window because you are symbolizing by an attribute Buffer distance in Meters. Although Buffer distance in Meters is always the same value, by default, it is treated as though it has multiple values. You can adjust the Size range slider for the symbols.

16. Close the Symbol style window.
17. In the Style options pane, for Size range, set the lower range to 24 and the upper range to 25.

    

    The symbol size is set to a more proportional size on the map.

18. Turn off the Include in legend option.

    

    The style for the Landslide Risk Areas layer is now configured.

    

Configure a pop-up for landslide risk areas

Next, you'll configure the layer's pop-up to convey only the information with which you enriched the layer.

1. In the Layers pane, ensure the Landslide Risk Areas layer is active. On the Settings toolbar, click Pop-ups.

   

2. In the Pop-ups pane, click Title and delete the existing text.
3. Click the add field button.

   

4. In the Add field window, click Name.

   The dynamic text {Name} appears in the Title.

5. At the end of the title, type Landslide Risk Area.

   

   The pop-up preview updates with the new title.

   

   Next, you will update which attributes to display in the pop-up.

6. In the Pop-ups pane, expand Fields list and click Select fields.

   

7. In the Select fields window, click Select all and click Deselect all.

   All the fields are not selected and you can choose the ones you want to display.

8. In the Select fields window, choose the following fields and click Done:
   • 2023 Total Population
   • 2023 Senior Population
   • 2023 Total Housing Units
   • 2023 Average Household Income
   • Relative Road Density

   

   The fields add to the Pop-ups pane and display in the pop-up preview.

   

   Next, you will update the format of the field values and remove the unnecessary decimal values.

9. In the Settings toolbar, click Fields.
10. In the Fields pane, click the 2023 Average Household Income field. In the Formatting window, for Significant digits, choose 0 Decimal places and click Done

    

11. Use what you have learned to update Significant digits to 0 Decimal places for the 2023 Senior Population and 2023 Total Housing Units fields.

    The Relative Road Density attribute indicates an average density of roads per square kilometer. Because it is depicting an average and not a whole number, such as people or households, you can keep it formatted with two decimal places.

    The pop-up is configured.

    

    The numbers displayed in this pop-up are merely estimates based on a generalized approximation of floodplains. However, they do provide a look at the devastating potential of flooding and landslide risk in this geologically tumultuous region.

12. Save the map.

Over the course of this tutorial, you identified the spatial relationships between different types of data both visually and analytically. You identified areas of flood and landslide risk in Boulder County and combined these areas with relevant information on demographics and infrastructure. Finally, you symbolized the data and configured pop-ups to communicate your results clearly and concisely, creating a finished web map that will inform users about the unique geologic conditions of the region.

You can find more tutorials in the tutorial gallery.

Acknowledgements

• All Adobe Stock images are © 2024 Adobe Stock. All rights reserved.
• Boulder County, Floodways, and Geologic Hazard Zones data from the Boulder County GIS Portal.
• Census Block Points: Esri; U.S. Department of Commerce, Census Bureau.
• Topographic map sources: Esri, HERE, Garmin, FAO, NOAA, USGS, Intermap, METI, OpenStreetMap contributors, and the GIS User Community