Explore the data and ask questions

When a volcano erupts, how much time do residents have to evacuate? That depends. Lava flows downhill and travels faster over steep ground. In the early 1990s, residents of Kalapana, a town in the southeastern Puna region, had days or even weeks to prepare for a lava flow that eventually covered the town. By contrast, a 1950 lava flow down the western flank of Mauna Loa reached the sea in about four hours. Although scientists monitor ground movement on the island continuously, there is no way to know how much advance notice residents living downhill of an eruption will receive.

Open the map and explore the data

First, you'll begin to explore the relationships among lava flow zones, emergency shelters, and population. By the end, you'll be ready to ask some questions that you'll answer in the remaining lessons.

  1. Go to the ArcGIS Online group, Analyze Volcano Shelter Access in Hawaii.
  2. Click the Content tab, then click the thumbnail of the Shelter Access Analysis map to open it.

    Shelter Access Analysis map

    The map opens to the island of Hawaii.

    Island of Hawaii

    As shown in the legend, the island is divided into nine categories of lava flow risk, from extremely high hazard to extremely low hazard. Under the partially transparent zones, census blocks symbolize population density (people per square mile) in shades of gray. The map also shows the locations of volcanoes and emergency shelters.

  3. If you are not signed in to your ArcGIS Organizational account, click Sign In and sign in with your ArcGIS Organizational account credentials.
    Note:

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

  4. On the map, click a volcano to see its pop-up.

    Volcano pop-up

    You see the volcano's name, elevation, type, and date of last eruption.

    Tip:

    In this example, the pop-up title bar shows "1 of 4". When you open a pop-up, you also access pop-ups for other features at or near the same location. (These may be in the same layer or different layers.) Click the white arrow in the title bar to see the other pop-ups.

  5. Open the pop-ups for the other volcanoes.

    Hualalai, Mauna Loa, and Kilauea are active. Mauna Kea is extinct. Loihi is also active, but since it’s undersea, it’s not a factor in this analysis.

  6. On the ribbon above the map, click the Bookmarks button and choose Kona.
  7. Open the pop-up for an emergency shelter.

    Emergency shelter pop-up

    Almost all the emergency shelters on the island are schools.

  8. Close the pop-up.
  9. On the ribbon above the map, click the Bookmarks button and choose Hilo – Puna.

    Hilo Puna bookmark

    The map zooms to the island’s east coast. Hilo is the island’s largest town, and most of the population lives in or near it. At this scale, the census blocks are easier to see under the hazard zone.

    Hilo Puna region

  10. Click a hazard zone to see its pop-up. (If a pop-up for a different layer appears, use the arrow in the pop-up title bar.)

    Lava flow hazard zone pop-up

    Hilo lies in a high hazard zone, as do the populated places to the south.

  11. Open pop-ups for the other lava flow hazard zones in the area.
  12. When you're finished, click the Bookmarks button and choose Kona.
  13. Open the lava flow hazard zone pop-ups in this area.

    The west coast is the other main population center on the island. Most of the people here live along the Kohala Coast, a medium-high hazard zone. Many also live in the high-hazard Mauna Loa Northwest Slope zone to the south.

  14. Use bookmarks to explore the other parts of the island. When you're finished, zoom to the Hawaii Island bookmark.

    As you start to work with analysis tools in the next lesson, you'll need to have your own copy of the map.

  15. On the ribbon, click the Save button and choose Save As.
  16. In the Save Map window, change the title to Shelter Access Analysis.

    Save map

  17. Click Save Map.

    The map is saved to your content page in the organization.

Many people, on different parts of the island, live in high-hazard lava flow zones. Usually, there are a good number of emergency shelters in these areas. But how accessible are these shelters? And how should accessibility be measured? Which high-risk parts of the island may need additional shelters? Next, you'll use analysis tools to evaluate shelter access for the brave mortals who put themselves in Pele's way.


Analyze shelter accessibility

Previously, you explored the relationship between lava flow zones, emergency shelters, and population. Next, you'll analyze accessibility by creating drive-time areas around the emergency shelters. Drive-time analysis uses either distance or expected travel time along a street network to show the area within reach of a given location or set of locations. You'll use a drive-time value of 15 minutes to define a shelter as easily accessible. This number was chosen somewhat arbitrarily, and you might want to repeat the analysis later with other values to see how the results change.

This analysis does not attempt to model emergency conditions. In a real emergency, all sorts of things may happen. Evacuation routes may be cut off by lava flow, roads may be jammed, emergency shelters themselves may lie in the lava flow path, and so on. Nonetheless, the ability to see which areas of the island have easy access to a shelter, and which do not, is a useful planning aid.

Create the drive-time layer

You'll continue working with the map you saved in the last lesson. If the map is already open in your browser, skip the first three steps about signing in and opening the map.

  1. If necessary, sign in to your ArcGIS organizational account.
  2. At the top of the page, click Content.
  3. In Content, click the ellipsis next to your web map and choose Open in Map Viewer.

    Open in Map Viewer

  4. If necessary, at the top of the Details pane, click the Content button.

    The Contents pane lists all the layers in the map and lets you work with their properties.

    Note:

    If you are continuing directly from the last lesson, the Details pane of your map will show the legend. If you opened the map from your Content page, it will show the contents. The Legend pane is useful for looking at the map; the Contents pane is useful for working with it.

  5. In the Contents pane, point to the Emergency Shelters layer and click the Perform Analysis button.

    Perform Analysis button
    Tip:

    You can also access the Perform Analysis pane from the ribbon.

  6. In the Perform Analysis pane, click Use Proximity and choose Create Drive-Time Areas.

    Create drive-time areas

  7. In the Create Drive-Time Areas pane, for Measure, confirm that Driving Time is the selected option. Change the time to 15 minutes.

    Change drive time to 15 minutes

  8. Leave the Use traffic box unchecked.
    Note:

    With the box unchecked, the analysis assumes that traffic flow is unimpeded and motorists observe the speed limit. These conditions probably wouldn't hold in an emergency, but you don't have a strong reason to base traffic conditions on a specific day or time.

  9. For Areas from different points, click Dissolve.

    Dissolve option

    The default Overlap option creates a unique drive-time area for each shelter. Dissolving the areas creates one output feature instead of many. The same total area will be covered.

  10. Name the result layer Shelter in 15 minutes and add your name or initials to the end to make it unique in the organization.

    Result layer name

    Tip:

    A unique name prevents your analysis result layer from conflicting with somebody else's in your organization.

  11. Click Run Analysis.

    When the analysis is finished, a new layer is added to the map. It shows the areas on the island that are within a 15-minute drive of a shelter.

    Drive-time layer on map

  12. In the Contents pane, point to the Shelter in 15 minutes layer. Click the More Options button and choose Rename.

    More Options button

  13. In the Rename window, change the layer name to Area within 15 Minutes of Shelter and click OK.

    Rename drive-time layer

  14. On the ribbon, click the Save button and choose Save.

Change symbols for the Census Blocks layer

You want to compare the area within 15 minutes of a shelter to populated areas of the island, but the map symbology makes that difficult. It will help to turn off the Lava Flow Hazard Zones layer. You can also change the way the census blocks are represented. Although the blocks are areas, it will be easier to see how well they're covered by the drive-time layer if you display them as points. (Essentially, you'll represent each block by its central point.)

  1. In the Contents pane, uncheck the box next to the Lava Flow Hazard Zones layer.

    Now it's easier to see the census blocks.

  2. In the Contents pane, click the Census Blocks layer name to show its symbology.

    Census block symbology

    Census blocks drawn in lighter shades of gray are less densely populated. High-density blocks tend to be small and clustered around Hilo.

  3. In the Contents pane, point to the Census Blocks layer and click the Change Style button.

    Change Style button

    In the Change Style pane, the attribute being symbolized is 2010 Population {Pop 10}. Because this attribute has been normalized by area, the values reflect the population density, not the total count, within each census block.

    Note:

    Normalizing by area is usually the best way to symbolize quantities that are contained within areas of different size. It creates an equal basis for comparing values.

  4. For a drawing style, select Counts and Amounts (Size), and then click Options.

    Counts and Amounts (Size) example

  5. For Size, choose Specify size range. Change the Min size to 6 px (pixels) and the Max size to 40 px.
  6. Click the Symbols button.

    Symbols button for the color palette

  7. In the Symbols window, click Fill and choose an orange-red color (#FF5500) to change the fill color of the symbol.

    New color palette

  8. Set the symbol transparency to 40%.
    Tip:

    Transparency can be applied to symbols within a layer (as here), to the layer as a whole, or to both.

  9. For the outline color, click Outline and choose white. Make sure the Line Width is 1 px (pixel).
  10. Click OK.
  11. Click the Polygons button to change the style of the Census Block boundaries.
  12. For Outline, choose No Color and click OK.

    Outline with No Color

  13. In the Change Style pane, click OK and click Done.

    On the map, the population of each census block is drawn as an orange circle. You don't see the block boundaries. Instead, the graduated circles give you a sense of how population is distributed on the island.

  14. Open the properties for the Census Blocks layer and choose Set Visibility Range.
  15. Click World and choose Cities (1:160,000). Click some white space in the Contents pane to close the properties.

    Set visibility

    On the map, the census block circles disappear and, in the Contents pane, the Census Blocks layer turns to gray because it's now inactive. The census block circles will reappear, and the layer will turn black to show it's active, when you zoom in.

  16. Zoom to the Hilo – Puna bookmark and, if necessary, zoom in so the census block circles reappear.

    Census blocks as graduated symbols

    This way of drawing the census blocks gives a strong visual impression of where people can and can't reach a shelter within 15 minutes.

  17. Save the map.

Change symbols for the Area within 15 Minutes of Shelter layer

The drive-time layer is at the top of the Contents pane, and therefore draws above the other layers in the map. As a general rule, layers of polygon features should be displayed below layers of point features. You'll move the drive-time layer down a few levels and change its color.

  1. In the Contents pane, click to the left of the Area within 15 Minutes of Shelter layer and drag the layer down until it's below all the layers except the Streets basemap.
  2. Point to the Area within 15 Minutes of Shelter layer and click the Change Style button.
  3. For a drawing style, under Location (Single symbol), click Options.
  4. Click Symbols to change the symbol.
  5. Click an orange-red color (#FF5500) to change the fill color of the symbol.

    Symbol settings

  6. Change the outline width to 0 px.
  7. Click OK.
  8. Change the transparency to 60%.
  9. Click OK and click Done to finish changing the symbol.

    Drive-time layer symbology on map

  10. Zoom to the Hawaii Island bookmark.
  11. Save the map.

You've already answered a couple of the questions you had. You measured shelter accessibility with a 15-minute drive time, and you can see on the map where populated areas lie inside and outside of this coverage. Next, you'll create a new layer that consists exclusively of high-hazard zones. This will help you focus on shelter accessibility in the areas of greatest risk.


Combine areas of high lava flow risk

Previously, you determined which areas had access to shelters. Next, you'll find which areas are at the greatest risk of lava flow. Most eruptions on the island occur at the summits and rift zones of volcanoes. Rift zones are areas where the volcano is splitting apart; the rock is weaker there and magma reaches the surface more easily. These zones are extremely high-hazard areas. Once lava makes it to the surface, it flows downhill and follows local topography. Areas downhill of rift zones are likely to be classified as either high-hazard or very high-hazard zones.

Hazard classifications represent the probability, based on historical evidence, that an area will be covered by lava in the event of an eruption. For this analysis, you'll treat the three highest-risk categories alike. You'll combine them into a single layer and mask out the lower-risk zones on the map.

Combining the three high-risk categories is a two-step process. With the Find Existing Locations tool, you'll build a query expression to find zones that meet the right conditions. You'll then use the Dissolve tool to combine these zones into a single feature.

View hazard zone attributes

Your query expression to find high-hazard zones will be based on attribute values (field values) in the table of the Lava Flow Hazard Zones layer. Before building the query, you'll look at the table to see how these values are stored.

  1. If necessary, open your Shelter Access Analysis map.

    Shelter Access Analysis map

  2. In the Contents pane, turn on the Lava Flow Hazard Zones layer by checking its box.
  3. Point to the Lava Flow Hazard Zones layer name and click the Show Table button.

    Show Table button

    The table opens below the map.

    Attribute table for lava flow hazard zone

    Tip:

    You can enlarge the table by dragging the white bar at the top of the table.

  4. Scroll through the table to see the values for the Severity attribute.

    You'll use this attribute name and the values in this field to build the query.

  5. When you're finished, point to the Lava Flow Hazard Zones layer and click the table button again to hide the table.

Find the high-hazard zones

Now you'll build the query with the Find Existing Locations tool. This tool finds features in a layer according to attribute values in the table or spatial relationships to features in another layer. In this case, you only need to work with attribute values. Features meeting the query conditions will be added to a new result layer.

  1. In the Contents pane, point to the Lava Flow Hazard Zones layer and click the Perform Analysis button.
    Tip:

    You can also access the Perform Analysis pane from the ribbon.

  2. In the Perform Analysis pane, click Find Locations, and click Find Existing Locations.

    Find existing locations tool

  3. In the Find Existing Locations pane, click Add Expression to open the Add Expression window.

    Add expression button

    In the Add Expression window, the top line is already set correctly: Lava Flow Hazard Zones where (attribute query).

    Add expression box

    What this means is that you want to find features in the Lava Flow Hazard Zones layer with certain, as yet unspecified, attribute values.

  4. On the second line of the expression, click the arrow to show the fields in the table and choose Severity. Leave the logical operator set to is.
  5. Under the empty input box, click Unique.

    Extremely high hazard expression

    The box changes to a drop-down list containing each unique value from the Severity field. The first value listed, Extremely High Hazard, is one of the ones you want. (The values are listed alphabetically.)

  6. Click Add.

    In the Find Existing Locations pane, the expression is added to the query.

  7. Click Add Expression again.
  8. In the Add Expression window, build the expression Lava Flow Hazard Zones where Severity is High Hazard. Click Add.

    High hazard expression

    The second expression is added beneath the first.

    Expression box with two expressions

  9. Click Add Expression again.
  10. Build the expression Lava Flow Hazard Zones where Severity is Very High Hazard. Click Add.

    Very high hazard expression

    The three relevant expressions have been added, but the query logic isn't right. You want to find features that meet any of these conditions, not features that meet all of them. (No features meet all three conditions, since a feature can have only one severity value.)

  11. In the Find Existing Locations pane, in the query box, click the first and operator to toggle it to or.

    Expression box with three expressions

  12. In the same way, toggle the second and to or.

    Completed expression

    Note:

    When two expressions are connected by "and," a feature is found only if it meets both conditions. When the expressions are connected by "or," a feature is found if it meets either condition. If you combine "and" and "or" operators in a query, you should group the expressions to make sure the logic is evaluated correctly. The Group tool is on the tool palette next to the Add Expression button.

  13. Name the result layer High Hazard Zones and add your name or initials to the end to make it unique within your organization.

    Result layer name

  14. Click Run Analysis.

    When the new layer is added to the map, you can see that it covers about half the island. It includes all features that have one of the three high-hazard values.

    High-hazard zones layer on map

  15. Rename the layer by removing your name or initials.
  16. Save the map.

Dissolve the high-hazard zones

The High Hazard Zones layer represents the area you want to explore more closely, but it still consists of several features with distinct boundaries. Since, for this analysis, you're treating high-, very high-, and extremely high-hazard zones as equally significant, you'll dissolve the layer into a new layer that contains a single feature.

  1. In the Contents pane, point to the High Hazard Zones layer and click the Perform Analysis button.
  2. In the Perform Analysis pane, click Manage Data and click Dissolve Boundaries.

    Dissolve boundaries

  3. In the Dissolve Boundaries pane, for step 2, accept the default option to dissolve areas that overlap or are adjacent. Ignore step 3 because you don't need any statistics.
  4. For step 4, name the result layer Combined High Hazard and add your name or initials. Click Run Analysis.

    Result layer name

    The new layer covers the same area as the High Hazard Zones layer, so you don't need the High Hazard Zones layer any more.

  5. In the Contents pane, point to the High Hazard Zones layer. Click the More Options button and choose Remove.
  6. In the Remove window, click Yes, Remove Layer.
  7. Rename the Combined High Hazard layer to High Hazard Zone.
  8. Save the map.

    Dissolved high hazard zones on map

Copy and filter the lava flow hazard zones

The island is now made up of two parts. The High Hazard Zone layer is the part you care about. The part you don't care about is everything else. You'll symbolize these two parts in distinct ways, but, in order to do so, you need to make a single layer from the part you don't care about—that is, all the medium- and low-hazard zones.

You could do this with the same method you used to create the High Hazard Zone layer (an attribute query followed by a Dissolve operation). Another way to do it is by applying a filter. Like the Find Existing Locations tool, a filter finds features in a layer according to their attribute values. Instead of creating a new result layer, however, the filter hides features that don't satisfy the query. A filter is a display property of a layer rather than a data creation tool.

You'll make a copy of the Lava Flow Hazard Zones layer and apply the filter to the copy. This copy is not a new dataset, but a cloned display of the Lava Flow Hazard Zones layer that is based on the same dataset. You can make many such copies from one and the same dataset and give each copy different layer properties. The copies can coexist in a web map or be saved as items to your Content page and used in different web maps.

  1. In the Contents pane, point to the Lava Flow Hazard Zones layer. Click the More Options button and choose Copy.

    A copy of the layer is added at the top of the Contents pane.

  2. Rename the Lava Flow Hazard Zones – Copy layer to Medium to Low Hazard Zone.
  3. In the Contents pane, point to the Medium to Low Hazard Zone layer and click the Filter button.

    Filter button

  4. In the Filter window, choose Severity from the list of fields.
  5. Change the logical operator to is not.
  6. Under the empty input box, choose Unique.

    The box changes to a drop-down list of values. The first value, Extremely High Hazard, is the one you want.

  7. Click Add another expression.

    Filter expression

  8. Set the second expression to Severity is not High Hazard.
  9. Add a third expression and set it to Severity is not Very High Hazard.

    Three filter expressions

    Note:

    In this case, a feature must meet all three conditions to be displayed. It must not be extremely high hazard and it must not be high hazard and it must not be very high hazard.

  10. Click Apply Filter.
  11. Turn off the Lava Flow Hazard Zones layer.
  12. Turn the High Hazard Zone layer off and on to confirm that this layer and the Medium to Low Hazard Zone layer are mutually exclusive.
  13. Save the map.

    Now you'll change the symbology of the Medium to Low Hazard Zone layer to de-emphasize it.

Change the hazard zone symbols

Cartographically, the map isn't doing what you want. Changing the symbols for the High Hazard Zone and Medium to Low Hazard Zone layers will make a big difference.

  1. In the Contents pane, point to the High Hazard Zone layer and click the Change Style button.
  2. For a drawing style, under Location (Single symbol), click Options.
  3. Click Symbols to change the symbol.
  4. Move the Transparency slider for the fill color of the symbol to 100%.

    Symbol settings

  5. Click Outline and choose an orange-red color (#FF5500). Confirm that the outline width is 2 px.

    Outline color to red

  6. Click OK.
  7. In the Change Style pane, change the overall transparency to 0%.

    Overall transparency to zero

  8. Click OK and click Done to finish changing the style.
  9. In the Contents pane, point to the Medium to Low Hazard Zone layer and click the Change Style button.
  10. Click the arrow next to Choose an attribute to show and choose Severity.

    Severity attribute

  11. For a drawing style, select Location (Single symbol), and then click Options.

    Location (single symbol) example

  12. Click Symbols to change the symbol.

    Symbol button

  13. Click the gray color (#C2C2C2) to change the fill color of the symbol, and set its transparency to 40%.

    Medium to Low Hazard Zone symbology

    Tip:

    The Fill option is automatically selected, as shown by the shading around Fill at the top of the dialog box.

  14. Click Outline.
  15. Uncheck the Adjust outline automatically setting. Choose No color, and then click OK.

    Outline with no color

  16. Click OK and click Done to finish.
  17. Move the Medium to Low Hazard Zone layer below the High Hazard Zone layer.
  18. Save the map.

    Contents pane and map

    The high-hazard zone is transparent with an orange outline, and the areas of medium to low risk are partially masked. The map is now focused on the areas you want to explore in greater detail.

Configure pop-ups

Before continuing with the analysis, you'll configure pop-ups for your layers as needed. When you share the map with others, they'll be able to click map features to get meaningful information.

  1. On the map, click somewhere in the high-hazard zone.

    High hazard zone pop-up

    This pop-up isn't good, but in any case, you don't really need a pop-up for this layer. Map users will know from the legend that this is the high-hazard zone. That's all the information they need.

  2. Close the pop-up.
  3. Open the properties for the High Hazard Zone layer and choose Remove Pop-up.
  4. Click again in the high-hazard zone to confirm that no pop-up appears.
  5. Click somewhere in a medium- to low-hazard zone.

    Medium to low hazard zone pop-up

    This layer has the same pop-up as the Lava Flow Hazard Zones layer it was copied from. You don't want a pop-up here, because you don't want map users paying attention to this part of the map.

  6. Remove pop-ups for the Medium to Low Hazard Zone layer.
  7. Zoom to the Hilo – Puna bookmark.
  8. Click a couple of emergency shelters and census blocks to see their pop-ups.

    Emergency shelter and census block pop-ups

    These pop-ups are already configured nicely.

  9. Click somewhere in the Area within 15 Minutes of Shelter layer to open its pop-up.

    Drive time pop-up

    This pop-up is important for interpreting the map, but the default configuration isn't helpful. You'll configure this pop-up with a custom attribute display that lets you combine your own text with values from the layer's attribute table.

  10. Close the pop-up.
  11. In the Contents pane, point to the Area within 15 Minutes of Shelter layer. Click the More Options button and choose Configure Pop-up.
  12. In the Configure Pop-up pane, change the Pop-up Title to Emergency Shelter Access Area.
  13. For Pop-up Contents, click the arrow next to Display and choose A custom attribute display.

    Pop-up properties

  14. Click Configure.
  15. In the Custom Attribute Display window, type This area is within a fifteen-minute drive of an emergency shelter under normal driving conditions. Click OK.
  16. At the bottom of the Configure Pop-up pane, click OK.
  17. Click the drive-time area again.

    Emergency shelter access area pop-up

  18. Close the pop-up.
  19. Zoom to the Hawaii Island bookmark.
  20. Save the map.

You've created a new layer and symbolized the map to focus attention on the high-hazard lava flow areas. Next, you'll examine the shelter locations and drive-time areas more closely.


Interpret and share results

Previously, you analyzed the physical side of lava flow risk. But what about the demographic side? The landscape and demographics of Hawaii are unique. Your map gives a good general impression of where people live and how accessible emergency shelters are, but you'll learn more from closer examination. Urban and rural locations on the island are close together. Population distribution is uneven and, in many places, infrastructure is simple. (For example, there are many unpaved roads.) Changing basemaps to look at both streets and imagery will give you a better understanding of the relationship among population, shelters, and the drive-time area.

Explore the western part of the island

You'll begin by exploring the southern part of the Kona Coast, around the town of Captain Cook, on the west side of the island.

  1. If necessary, open your Shelter Access Analysis map.
  2. Zoom to the Kona bookmark. Pan slightly south to focus on the High Hazard Zone.
  3. Open the table for the Emergency Shelters layer. Click the Name heading, and choose Sort Ascending. Scroll down, and click the Konawaena High School row to select the feature in the map.
  4. Click the selected feature in the map to open its pop-up and then click Zoom to. Close the pop-up and close the table.
  5. Click a census block symbol that lies outside the drive-time area.

    Census block pop-up

    When you click the symbol, the census block polygon is highlighted. In this example, part of the block lies inside the drive-time area and part lies outside. Although you know that 65 people live within the block, you don’t know exactly where they live. Some, none, or all of them may live within fifteen minutes of the nearby shelter.

  6. On the ribbon, click the Basemap button and choose Imagery.
  7. Click the same census block symbol as before. On the pop-up, click Zoom to.

    Census block on imagery basemap

    The map zooms in on the selected census block.

  8. Change the transparency on the Area within 15 Minutes of Shelter layer to 80%.

    Census block boundary

    At this zoomed-in scale, you can see the locations of buildings. For this census block, it looks like almost all of them are located within the drive-time area.

  9. Pan the map and examine some other census blocks in the area.

    Many of the blocks are large and lightly populated. Judging by the locations of structures, it looks like most of the people in this area do live within the 15-minute drive-time area.

Explore the southern part of the island

The Kau region, in the south and southeastern parts of the island, is rural, remote, and sparsely populated.

  1. Zoom to the South Kona – Kau bookmark.
  2. Change the basemap to Streets.
  3. Change the transparency on the Area within 15 Minutes of Shelter layer to 50%.

    South Kona-Kau

    Even without closer inspection, it’s clear that most of the people in this part of the island do not live within 15 minutes of a shelter.

  4. Turn the Lava Flow Hazard Zones layer on.

    Hawaiian Ocean View subdivision

    The Hawaiian Ocean View subdivision, at the southern tip of the island, is adjacent to the Mauna Loa Rift Zone, an extremely high-hazard zone. This is a place where it might be useful to locate a shelter.

  5. Turn off the Lava Flow Hazard Zones layer.

Find the population of the Hawaiian Ocean View subdivision

It would be interesting to know how many people live in this remote subdivision—and it might strengthen the argument that an emergency shelter should be located nearby. To get the population, you can interactively draw a boundary around the subdivision, then summarize the population inside.

  1. On the ribbon, click the Add button and choose Add Map Notes.
    Note:

    Map notes are features and text that you add to a map interactively.

  2. In the Add Map Notes window, change the name to Hawaiian Ocean View, and click Create.

    Add map notes

  3. In the Add Features pane, click the Area symbol.

    Area symbol

  4. Click the map somewhere outside the cluster of census block symbols to begin drawing a polygon. Move the mouse pointer to start drawing the boundary, and click again to add a corner and change direction.
  5. Continue drawing a polygon that surrounds the subdivision. When you're done, double-click to finish the feature.
  6. Click Close on the map note pop-up. (Or click Delete if you need to start over.)

    Selected map note

    Your map note should look more or less like the one in this example.

  7. On the ribbon, click the Details button to stop adding map notes.
  8. In the Contents pane, point to the Hawaiian Ocean View layer and click the Perform Analysis button.
    Tip:

    You can also access the Perform Analysis pane from the ribbon.

  9. In the Perform Analysis pane, click Summarize Data and click Summarize Within.
  10. In the Summarize Within pane, for step 2, choose Census Blocks as the layer to summarize.
  11. For step 3, change Field to 2010 Population and change Statistic to Sum.

    Summarize Within settings

    The result will be a layer with the same shape as the Hawaiian Ocean View layer but with a total population value for the census blocks inside the polygon boundary.

  12. Name the result layer Summarize Population and add your name or initials. Click Run Analysis.

    Result layer name

    The new layer is added to the Contents pane under the Hawaiian Ocean View layer. (Layers created from map notes always stay at the top of the list.)

  13. Remove the Hawaiian Ocean View layer from the map.
  14. In the map, click the Summarize Population layer to open its pop-up.

    Summary of census blocks pop-up

    The population of the subdivision is 4,438. Now that you have this piece of information, there's no need to keep the layer in the map.

    Note:

    Your population value may vary slightly.

  15. Remove the Summarize Population layer and save the map.

Explore the eastern part of the island

The eastern part of the island includes the town of Hilo, home to about 40,000 people.

  1. Zoom to the Hilo – Puna bookmark, then zoom in a couple of levels on the town of Hilo.

    Hilo

    It looks as if nearly all of Hilo is within the 15-minute access zone.

  2. Pan south to the area south of Kurtistown and east of Mountain View.

    Here, for reasons that aren’t entirely clear, many of the streets are not covered by the drive-time area.

  3. Change the basemap to OpenStreetMap.

    OpenStreetMap basemap

    The main road in this area is HI 11. This is a divided highway and is depicted as a cased yellow line. Highways allow faster travel and have higher speed limits. The roads in the Hawaiian Acres area are drawn with narrow lines to indicate that they are narrower, less improved roads with lower speed limits. The drive time analysis takes speed limit into account, so areas served by these roads are more remote in terms of drive time.

  4. Continue exploring different parts of the map with these three basemaps, and others if you like.
  5. When you’re finished, change the basemap to Streets, and zoom to the Hawaii Island bookmark.
  6. Save the map.
  7. On the ribbon, click the Share button.
  8. In the Share window, share the map with your organization or with everyone.

    Share window

    When you share the map, the Update Sharing window opens, which indicates that the layers that you own may not be visible to others because they are not shared in the same way as the map.

  9. Click Update Sharing to adjust the settings of the listed layers so they can be viewed in the web map.

    Once the map is shared, you can enhance the user experience by making a web application.

  10. Click Done.

In this lesson, you explored the relationship among population, emergency shelters, and high-risk lava flow zones. You evaluated the accessibility of shelters using drive-time analysis. You used other analysis tools to combine the highest-risk zones into a single layer on the map and symbolized this layer to facilitate further exploration. By zooming in and changing basemaps, you were able to see how well the shelter access area covered populated places. You identified an area of the map where a new shelter might be needed, and you found a plausible explanation for why parts of the street network near the town of Mountain View were not accessible to shelters.

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