Assessing the damages of La Palma Volcano

Context

Since 11 September 2021, a swarm of seismic activity had been ongoing in the southern part of the Spanish Canary Island of La Palma (Cumbre Vieja region). The increasing frequency, magnitude, and shallowness of the seismic events were an indication of a pending volcanic eruption; which occurred on 16th September, leading to evacuation of people living in the vicinity.

In this tutorial we are going to assess the number of buildings and population that may get affected by the lava flow and its deposits. We’ll also estimate the value of damaged residential properties affected by the volcano eruption.

Step-by-Step Guide:

1. Access the Data Explorer section from your CARTO Workspace using the navigation menu.

2. In the Data Explorer page, navigate to CARTO Data Warehouse > demo_data > demo_table.

In this tutorial, we are going to use the following 3 tables:

• lapalma_buildings: it contains the buildings in La Palma as obtained from the Spanish cadaster website;

• lapalma_sociodemo_parcels: it contains a sample from Unica360’s dataset in the Data Observatory “Cadaster and Sociodemographics (Parcel)”;

• lapalma_volcano_lavaflow: it includes the lava flow from the Volcano eruption in La Palma, Spain as measured by the Copernicus satellite on 10/04/2021.

3. Spend some time exploring the three tables in the Data Explorer.

4. Select lapalma_buildings and click on "Create map" button on the top.

This will open CARTO Builder with this table added as a layer to a map.

5. Rename the layer to “La Palma Buildings” and the map title to "Assessing the damages of La Palma Volcano"

6. Click on the layer to access the layer panel. In this section, you can style the layer according to your preferences. We have set the Fill Color to purple, reduce the opacity to 0,1. Then, we have set the Stroke Color to dark blue.

7. Let's add the lapalma_sociodemo_parcels source. To do so, follow the below steps:

   • Select the Add source from button at the bottom left on the page.

   • Click on the Data Explorer option.

   • Navigate to CARTO Data Warehouse > demo_data > demo_tables. Search for lapalma_sociodemo_parcels. Once you find it, select it and click on "Add Source".

8. Once added, a new layer appears on the map. Rename it to "La Palma demographics".

9. We'll now change the style of La Palma demographics layer. Access the layer panel and set the Fill Color to green and the Outline color to black. Also reduce the Stroke width to 1. Then, style the size of the points based on the population living in the parcel. To do so, select p_t column in the Radius section and set the range from 2 to 25.

Now, we are looking to analyse the number of buildings, their estimated values for residential properties and total population affected by the volcano lava extent. To perform this analysis, we'll use Workflows.

10. Go back to the Workspace tab in your browser and access Workflows.

11. In Workflows page, use the "New workflow" button to start a new Workflow. Select CARTO Data warehouse as the connection you want to work with.

12. From the Sources panel located on the left side, navigate to CARTO Data Warehouse > demo_data > demo_tables and locate lapalma_volcano_lavaflow. Drag and drop the source table into the canvas.

13. Repeat Step 13 to add lapalma_buildings into the canvas.

14. Now, use Enrich Polygons component to obtain the total of estimated property value of those residential properties affected by the lava flow as well as the total number of buildings affected. Connect lapalma_volcano_lavaflow as the target polygon and lapalma_buildings as the source. In the Variables section, in the node, add SUM for estimated_prop_value column and COUNT aggregation for numberOfBuildingUnits column. The output result is the lava flow source with the addition of the two new properties.

15. Add lapalma_sociodemo_parcels source to the canvas.

15. To obtain the total population affected by the lava flow extent, we will add the Enrich Polygons again. This time, we'll link lapalma_volcano_lavaflow as the target and lapalma_sociodemo_parcels as the source. Then, in the Variables section add SUM of p_t column.

16. Using the Join component, we'll join both Enriched Polygons output in a single table using the geoid as the common column. To achieve that, add the Join component to the canvas, use geoid as the common column for both sources and select Inner as the join type.

17. Save the output result as a new table using the Save as Table component. Set the destination to Organization > Private of your CARTO Data Warehouse and rename the output table to lapalma_volcano_lavaflow_enriched. Then, click on "Run".

17. Now, in the same Workflow, let's perform another analysis. This time, we are going to create a 500 meter buffer around the lava flow, and perform the same aggregations as we have done on Step 14 and Step 15 to compute the total number of buildings and the estimated damaged value of the residential properties within this larger region. To do so, add the Buffer component and link it to lapalma_volcano_lavaflow source. Set the distance to 500 meters. Then, click on "Run".

16. Afterwards, we'll add Enrich Polygons component, this time connecting the Buffer output as the target source. In the source input we'll connect lapalma_buildings source. Add the same aggregated variables: SUM for estimated_prop_values and COUNT for numberOfBuildingUnits. You can review the output in the Data Preview.

17. Let's add Enrich Polygons component again, this time to enrich the buffered output of La Palma lava flow with La Palma sociodemographics. In the Variable section of the Enrich Polygons component, add SUM for p_t to obtain the population affected by this buffered extent.

18. We'll add the Join component to join the output from both Enrich Polygons components. In the Join node, select geoid as the common column from both inputs and set the Join type to Inner.

19. Use the Select component to keep just the necessary columns using the below statement:

geoid,
geom_buffer as geom, 
estimated_prop_value_sum,
numberOfBuildingUnits_count,
p_t_sum_joined

20. Finally, save the results as a table using the Save as Table component. Navigate to CARTO Data Warehouse > organization > private and save your table as lapalma_volcano_lavaflow_enriched_buffer.

20. Now let's go back to Builder. We'll first add lapalma_volcano_lavaflow_enriched as a table data source following the below steps:

    • Access Add source from..

    • Click on the Data Explorer option.

    • Navigate to CARTO Data Warehouse > organization > private. Search for lapalma_volcano_lavaflow_enriched. Once you find it, select it and click on "Add Source".

21. A new layer is added to the map. Rename it to "Lava flow" and move it to the bottom, just below La palma buildings layer.

22. Access Lava flow layer panel and set the Fill Color in the layer styling to light red.

23. Now let's add the enriched lava flow which was buffered by 500 meters. To do so, follow

    these steps:

    • Access Add source from..

    • Click on the Data Explorer option.

    • Navigate to CARTO Data Warehouse > organization > private. Search for lapalma_volcano_lavaflow_enriched_buffer. Once you find it, select it and click on "Add Source".

24. Rename the recently added layer to 'Lava flow buffer' and move it to the bottom, just below Lava flow layer.

25. Set the layer style for Lava flow buffer to very light red. To do so, access the Layer panel and pick the color in the Fill Color section. Also, set the opacity in this section to 0.3 and disable the Stroke Color using the toggle button.

26. In the Interactions tab, enable interactions for both Lava flow and Lava flow buffer layers. For each column, set the right formatting and rename it to a user-friendly label.

27. Change the basemap to Google Terrain by navigating to the Basemap tag and selecting Terrain type.

28. Now, we can add a map description to provide further context about this map to our viewer users. You can use the below markdown description or add your own.

### La Palma Volcano Eruption Impact Analysis 🌋

![Image: Global Populated Places](https://app-gallery.cartocdn.com/builder/lapalmavolcano.jpg)

This interactive map provides an in-depth visualization of the impact caused by La Palma volcano eruption which took place in 2021. It helps understanding the extent of the eruption's effects on the local community and environment.

---
🔍 **Explore the Map to Uncover**:

- **🌋 Volcano Lava Flow Visualization**: Trace the path of the lava flow, providing a stark visualization of the affected zones.

- **🔴 Buffered Lava Flow Zone**: View the 500-meter buffer zone around the lava flow, marking the wider area influenced by the eruption.

- **🏠 Building and Parcel Analysis**: Investigate how buildings and sociodemographic parcels in La Palma were impacted, revealing the eruption's reach on properties and people.

- **💡 Interactive Insights on Impact**: Engage with the lava flow areas to discover key data, such as the estimated value of affected properties, the number of properties impacted, and detailed population statistics.

---
📚 **Interested in Replicating This Map?**
Access our tutorial in the CARTO Academy for step-by-step guidance.

28. Finally we can make the map public and share the link to anybody in the organization. For that you should go to “Share” on the top right corner and set the map as Public. For more details, see Publishing and sharing maps.

Finally, we can visualize the result!