GIS Activity #2 - Houston, TX Hurricane Routes
A new map opens.
Tip:
If you're in a new session, clicking Map will open a new map. Otherwise, it will open an existing map (the last map you were using). If an existing map opens, click New Map.
Your map's appearance varies based on your account or organizational settings and your browser window size. It may show the United States (such as in the example image), the world, or another extent. The only layer on the map is the basemap, which provides geographic context such as water bodies and political boundaries. The default basemap is Topographic, but your map may have a different basemap depending on your organization's settings.
Above the map is the ribbon. To the left side of the map is the Details pane, which provides information about the map and its layers. Next, you'll navigate to your area of interest.
Note:
Some ArcGIS organizations have custom address locators. You may encounter different search results than those in the example image.
The map zooms to Houston. A Search result pop-up confirms the location.
- Close the Search result pop-up.
Add a layer
Next, you'll add a layer to your map that shows hurricane evacuation routes in Houston. You'll add this layer from ArcGIS Living Atlas of the World, a collection of curated geographic data from around the globe.
- On the ribbon, click Add and choose Browse Living Atlas Layers.
The search pane appears. The layer you want to add is owned by the Federal User Community, an ArcGIS account that contains United States governmental data. You can find the layer more easily by adding the name of the layer's owner to the search terms.
- Confirm that Living Atlas is displayed at the top of the pane
- In the search box, type Hurricane Evacuation Routes. Then, type owner:Federal_User_Community.
- Press Enter.
The search returns a single result.
- For the Hurricane Evacuation Routes layer, click the Add button.
The layer is added to the map.
The routes are displayed as dark gray lines that travel throughout the city, but they don't stand out clearly against the Topographic basemap. You'll change the basemap to one with a lighter color scheme so the routes stand out.
- In the search pane, click the Back button. Click the Show Contents of Map button.
The Contents pane appears. It lists all layers on the map, including the basemap.
- On the ribbon, click Basemap and choose Light Gray Canvas.
The basemap changes. The evacuation routes stand out much more against the lighter-colored, less-detailed basemap.
Navigate the map
Before you explore, you'll create a bookmark of the current extent so you can quickly return to it when needed.
- On the ribbon, click Bookmarks and choose Add Bookmark.
A text box for the bookmark's name appears.
- In the text box, type Houston and press Enter.
The bookmark is added. You can choose this bookmark to automatically navigate to the map extent where the bookmark was created.
- Close the Bookmarked places window.
You're now ready to explore the city.
- Zoom in to the center of the city, near the Houston label, until the Buffalo, Brays, and White Oak Bayous appear on the map.
Tip:
There are several ways to zoom. You can click the Zoom In button in the corner of the map or scroll up with the mouse wheel. Alternatively, you can press Shift while drawing a box around the area you want to zoom to.
- If necessary, pan the map until all three bayous are visible.
Houston has several major bayous (flat, low-lying marshes or wetlands). During a hurricane, these bayous are prone to flooding and can become especially dangerous. You may want to keep this area in mind when you later identify high-risk areas.
- Add a bookmark for the current map extent. Name the bookmark Bayous.
- On the ribbon, click Bookmarks and choose Houston.
The map zooms to its original extent.
Change the style
Although the evacuation routes stand out more against the light basemap, they could be even more eye-catching. You'll change the layer's style, also known as its symbology, to give the routes a brighter color and a thicker line width.
- In the Contents pane, point to the Hurricane Evacuation Routes layer and click the Change Style button.
The Change Style pane appears. Layers can have either a single symbol or multiple symbols based on attribute information such as names or speed limits. You'll learn more about attribute information later. Right now, you're only interested in showing the location of roads, not particular characteristics of each road, so you'll continue to symbolize the layer with a single symbol.
- For Location (Single symbol), click Options.
The pane changes to provide multiple style options, such as the layer's transparency or the range of map extents at which it is visible. You'll change the color and size of the symbol itself.
- Click Symbols.
A window appears with a color palette and other options.
- On the color palette, choose the blue color on the bottom row, fourth column from the right.
After you choose the color, the six-character hexadecimal code changes to #004C73.
- For Line Width, choose 3 px.
- Click OK.
The new line color and width are applied to the layer.
- In the Change Style pane, click OK. Then, click Done.
With the thicker, brighter symbol, the routes are eye-catching and stand out.
The routes layer is a feature layer, which means it consists of individual features with distinct characteristics. In this case, each route segment is a feature. You can view a feature's characteristics, also known as its attribute information, by clicking the feature on the map and opening its pop-up.
- Click a segment of an evacuation route.
Its pop-up appears.
From the pop-up, you learn the name of the route (in the example image, I-45), as well as whether the route is paved and what type of road it is. The owner of the Hurricane Evacuation Routes layer specifically configured this pop-up to present attribute information in a clear and readable way. You'll learn how to configure pop-ups in a later lesson.
- Click a few route segments to view their pop-ups. When finished, close the pop-up.
Add demographic data
Next, you'll determine areas of the city that are likely in need of evacuation assistance. To do so, you'll add a layer containing demographic data by census tract. United States census tracts divide counties into smaller geographic areas, which are useful for revealing spatial patterns.
- On the ribbon, click Add and choose Search for Layers.
Unlike the routes layer, the demographic data you'll add isn't in the Living Atlas. Instead, it's owned by the Learn ArcGIS administrator account.
- At the top of the pane, choose ArcGIS Online.
- In the search box, clear any existing search text and type Houston Census Tract Demographics owner:Learn_ArcGIS. Press Enter.
- Add the Houston Census Tract Demographics layer.
Note:
It may take a few moments for the layer to appear on the map.
The layer is added to the map. It's styled by location and shows all census tracts with a single color. Right now, the layer doesn't tell you anything or provide any insight into areas in need of evacuation assistance.
- Click the Back button.
The new layer is listed in the Contents pane above the Hurricane Evacuation Routes layer you added in the previous lesson.
Layers are drawn on the map in the same order they appear in the Contents pane. In your map, the evacuation routes are partially covered by the census tracts because the Houston Census Tract Demographics layer is above the Hurricane Evacuation Routes layer in the Contents pane (you can still see the routes somewhat because the census tracts layer is transparent). To better see the routes, you'll reorder the layers.
- In the Contents pane, point to the Hurricane Evacuation Routes layer, click the More Options button, and choose Move up.
Tip:
You can also reorder layers in the Contents pane by dragging them.
The layers are reordered and the evacuation routes are now displayed on top of the census tracts on the map.
Next, you'll look at the layer's attributes. Every layer has a table that contains all attribute data about the geographic features in the layer. You'll view the table for the Houston Census Tract Demographics layer to find data that will help you identify areas that are vulnerable during a hurricane.
- In the Contents pane, point to the Houston Census Tract Demographics layer and click the Show Table button.
The layer's attribute table opens. Each row in the table represents a feature (in this case, a census tract area). The columns, or fields, provide different types of information about the census tract features. For example, the FIPS Code field contains a code that represents the state, county, and census tract identifier for each census tract feature, and the Total Owner/Renter Households (ACS 2013-2017) field shows the total number of households in each tract.
Tip:
To make the table larger, drag the top of the table.
- If necessary, use the scroll bar at the bottom of the table to scroll all the way to the right.
- Locate the Percent of Households without a Vehicle field.
This field shows the percentage of households in each tract that do not own a vehicle. Areas with a high percentage of people who don't own vehicles might need help evacuating, so you'll style the layer using the values in this field.
- Close the table. In the Contents pane, point to the Houston Census Tract Demographics layer and click the Change Style button.
The Change Style pane appears. When you styled a layer previously, you styled evacuation routes with a single symbol based on location. This time, you'll choose an attribute and style the census tracts with multiple symbols.
- For Choose an attribute to show, choose Percent of Households without a Vehicle (ACS 2013-2017).
Based on the attribute you chose, several styles become available. The list of available styles is determined by your type of data, a process known as smart mapping. In this case, the recommended smart mapping style is Counts and Amounts (Color), which is marked by a blue check mark and applied to the map. This style symbolizes each census tract with a different color based on households without a vehicle.
The colors are based on a color ramp called High to Low. Census tracts with the lowest values have a light color, while those with the highest values have a dark color.
Note:
Your default colors may differ from those in the example image.
The default color ramp can make it difficult to see the evacuation routes in areas with high percentages, so you'll change the color ramp to ensure all layers remain visible throughout the map.
- For Counts and Amounts (Color), click Options. In the more advanced options, click Symbols.
A window appears with options to change the fill color and outline of the symbols on the map. You'll choose a blue-themed color ramp to match the evacuation routes.
- For Fill, in the color ramp selector, click the blue-to-gray color ramp.
- Click OK.
The new color ramp is applied to the map.
In this map, census tracts with a higher-than-average percentage of households without a vehicle stand out in blue. Based on the legend, the average percentage is about 6 percent. A clear pattern of limited access to vehicles stands out in downtown Houston, close to the geographic center of the city. These census tracts would likely benefit the most from increased evacuation assistance, such as public transportation.
- In the Change Style pane, click OK. Then, click Done.
Now that the layer is styled to show the percentage of households without a vehicle, you'll give it a more descriptive name.
- In the Contents pane, point to the Houston Census Tract Demographics layer. Click the More Options button and choose Rename.
- In the Rename window, type Percentage of Households Without a Vehicle and click OK.
The layer name is updated in the Contents pane.
Save and share the map
Next, you'll save your evacuation map and assign it a title, tags, and a summary to make it easy to find and identify later. Then, you'll share the map to make it accessible.
- On the ribbon, click the Save button and click Save As.
The Save Map window appears.
- For Title, type Houston Evacuation Map.
Next, you'll add tags. Tags are terms that allow users to search for your map on ArcGIS Online.
- For Tags, type each of the following tags, pressing Enter after each one:
- Hurricanes
- Roads
- Evacuation Routes
- Houston
The summary appears on your map's details page and should provide information so users better understand your map's purpose.
- For Summary, type This map shows hurricane evacuation routes in Houston, Texas.
- Click Save Map.
The map is saved. It now appears in your account's content. You can access your content by clicking ArcGIS (public account) or Home (organizational account) and choosing Content. For now, you'll set the sharing permissions.
- On the ribbon, click the Share button.
- In the Share window, check Everyone (public).
- Click Done.