Exercise 4: Visualizing Cyclone Impact Results – Aina Styles Her Layers#

Characteristics of the exercise#

Type of trainings exercise:

  • This exercise can be used in online and presence training.

  • It can be done as a follow-along exercise or individually as a self-study.

Exercise Track:

This exercise is part of the Madagascar Anticipatory Action Cyclon Analysis Exercise Track

Estimated time demand for the exercise

Relevant Wiki Articles

Aim of the exercise:

Aina, the GIS expert at the Malagasy Red Cross (CRM), is preparing for the upcoming cyclone season. She wants to improve her team’s ability to act quickly once a storm is forecasted by automating key analyses in QGIS. These include estimating exposed populations, identifying impacted services like health and education, and assessing whether health posts can be reached from key warehouses within a critical 10-hour window. The goal is to prepare an end-to-end analysis and visualization workflow that can support fast, data-driven anticipatory action before a cyclone makes landfall.

Instructions for the trainers#

Trainers Corner

Prepare the training

  • Take the time to familiarise yourself with the exercise and the provided material.

  • Prepare a white-board. It can be either a physical whiteboard, a flip-chart, or a digital whiteboard (e.g. Miro board) where the participants can add their findings and questions.

  • Before starting the exercise, make sure everybody has installed QGIS and has downloaded and unzipped the data folder.

  • Check out How to do trainings? for some general tips on training conduction

Conduct the training

Introduction:

  • Introduce the idea and aim of the exercise.

  • Provide the download link and make sure everybody has unzipped the folder before beginning the tasks.

Follow-along:

  • Show and explain each step yourself at least twice and slow enough so everybody can see what you are doing, and follow along in their own QGIS-project.

  • Make sure that everybody is following along and doing the steps themselves by periodically asking if anybody needs help or if everybody is still following.

  • Be open and patient to every question or problem that might come up. Your participants are essentially multitasking by paying attention to your instructions and orienting themselves in their own QGIS-project.

Wrap up:

  • Leave time for any issues or questions concerning the tasks at the end of the exercise.

  • Leave some time for open questions.

Aina now has all the analysis results she needs — but numbers and tables alone won’t convince her colleagues or decision-makers. What they need are clear and easy-to-read maps that can be used directly in meetings and reports.

To save time, Aina doesn’t want to adjust colors and legends manually each time a new cyclone comes in. Instead, she will use ready-made style files (.qml) that instantly give layers a professional and consistent look. Where no style exists yet, she will create one herself, so that next time the map can be updated with just a few clicks.

In this task, you will help Aina make her cyclone impact maps both informative and visually compelling by applying and creating QGIS style files.

Tasks#

1. Load Required Layers (if not already loaded)#

Make sure the following layers are already loaded into your QGIS project. These are outputs from Task 3:

  • example_Harald_2025_Track

  • cyclone_harald_buffer

  • Harald_Exposed_Population

  • admin2_health_affected

  • admin2_education_affected

If any are missing:

  • Load them using drag & drop from your results folder, or

  • Use Layer → Add Layer → Add Vector Layer or Add Raster Layer

2. Apply Predefined Style Files#

Apply the following.qml style files to the respective layers:

Layer

Style File

example_Harald_2025_Track

storm_track_cyclone_style.qml

cyclone_harald_buffer

exposed_cyclone_area_style.qml

Harald_Exposed_Population

exposed_population_style.qml

admin2_health_affected

exposed_healthsites_style.qml

admin2_education_affected

exposed_education_facilities_style.qml

Note

⚠️ For the health and education facilities, the provided style files are linked to the column containing the sum of exposed facilities.
They are not based on the percentage column.

Steps:

  • Right-click on the layer in the Layers Panel

  • Select Properties

  • In the window that opens, go to the Symbology tab

  • At the bottom left, click Style → Load Style…

  • Click on the three points

  • Navigate to the corresponding .qml file in the folder layer_sytleand select it

  • Click Open, then Apply and OK to confirm

💡 If the style doesn’t load correctly, double-check the column names and make sure the column name used in the .qml file matches the one in your layer. To do this, open the Attribute Table of the layer and compare field names.

../../_images/fr_MDG_AA_intermediate_result_model_task4_exposed_pop_style.PNG

Carte montrant le nombre de personnes exposées par district après l’application du style .qml.#

../../_images/fr_MDG_AA_intermediate_result_model_task4_exposed_HS_sum_style.PNG

Carte indiquant le nombre total d’établissements de santé exposés par district, représentés avec le style prédéfini.#

../../_images/fr_MDG_AA_intermediate_result_model_task4_exposed_ES_sum_style.PNG

Carte affichant le nombre total d’établissements scolaires exposés par district, après application du fichier de style .qml.#

3. Style Percentage Layers Manually#

Aina also wants to visualise the percentage of exposed health and education facilities. However, since there is no prepared style available, she must complete the process manually.

Steps:

  • Right-click on the layer admin2_health_affected → select Duplicate Layer

  • Rename the duplicated layer to:

    admin2_health_affected_percentage

  • Right-click on the layer in the Layers Panel

  • Select Properties

  • In the window that opens, go to the Symbology tab

  • Set Symbology to Graduated

  • Choose the correct field:

    • pct_health_affected

  • Open the Histogram tab to view the value distribution by clicking on calculate histogram

  • Next go back to Classes and set the following configuration:

    • Mode: Equal Interval

    • Classes: 4

  • Click OK.This will create four classes (0–25%, 25–50%, 50–75%, 75–100%)

  • Choose a color ramp (e.g., light yellow → dark red)

  • Optionally customize class labels for clarity

  • Click Apply

  • Repeat the same process for the layer admin2_education_affected. After duplicating the layer, rename the new one to:

admin2_health_affected_percentage

🧠 Why 4 equal classes?
This helps visualize severity across districts using simple and interpretable risk categories. However, you can experiment with Natural Breaks if data is unevenly distributed.

4. Save Your New Styles for Reuse#

Save your manually created styles as .qml files for future reuse.

Steps:

  • Right-click on the layer in the Layers Panel

  • Select Properties

  • In the window that opens, go to the Symbology tab

  • Click on Style → Save Style…

  • Save the file in the folder layer_sytle

  • Use these filenames:

    health_pct_affected_style

    education_pct_affected_style

5. (Optional) Import Styles into Your QGIS Library#

To reuse your styles in any future project:

  • Go to Settings → Style Manager

  • Click Import/Export → Import Items

  • Browse to and select your saved .qml files

The styles will now appear as presets in the Layer Styling Panel.