Reunion

Climate risk and vulnerabilities of Réunion

Réunion is highly exposed to climate and multi-hazard risks because of its location in the south-west Indian Ocean cyclone basin, steep volcanic terrain, intense tropical rainfall, short and fast-reacting river catchments, active volcano, narrow coastal development zones, and concentration of people, roads, utilities, tourism assets, and public services between the mountains and the sea. Official French risk documents identify Réunion as exposed to most major natural hazards, including floods, landslides, cyclones, storms, earthquakes, volcanic activity, and forest fires. (Reunion)

Réunion is highly exposed and vulnerable to climate change and multi-hazard risks due to its location in the south-west Indian Ocean cyclone basin, steep volcanic terrain, intense tropical rainfall, short and fast-reacting river catchments, active volcanic system, narrow coastal development zones, and concentration of people, infrastructure, tourism assets, and public services in hazard-prone areas. The island faces recurrent risks from tropical cyclones, extreme rainfall, flash floods, landslides, rockfalls, coastal erosion, marine submersion, sea-level rise, drought, wildfires, heat stress, earthquakes, and volcanic eruptions. Climate change is expected to intensify these vulnerabilities through stronger rainfall extremes, warmer temperatures, coastal impacts, drought stress, wildfire risk, and increasing pressure on transport corridors, water systems, energy networks, settlements, ecosystems, tourism, and vulnerable communities. Strengthening multi-hazard early warning systems, impact-based forecasting, flood and landslide risk reduction, coastal adaptation, volcanic monitoring, resilient infrastructure, risk-informed land-use planning, disaster risk financing, and locally led preparedness is essential to reduce losses and protect Réunion’s communities and development gains.

1. Multi-hazard exposure

Réunion’s risk profile is unusually complex for a small island. The main hazards include cyclones, intense rainfall, floods, landslides, rockfalls, coastal submersion, coastal erosion, volcanic eruptions, earthquakes, drought, forest fires, and heat stress. French state risk-planning materials note that the island’s geography and geology expose it to volcanoes, cyclones, landslides, floods, and forest fires, while ORSEC emergency planning includes specific arrangements for volcanic, flood, cyclone, tsunami, weather-warning, and terrain-movement risks. (Les services de l’État à La Réunion)

Réunion’s volcanic origin and rugged topography are central to its hazard profile. A BRGM geological-risk report identifies cyclones, heavy rainfall, forest fires, landslides, floods, volcanic eruptions, and earthquakes as key hazards, while also emphasizing that slope movements are a major risk in steep escarpments, cirques, ravines, cliffs, and riverbanks. (InfoTerre)

2. Tropical cyclones, extreme rainfall, and flood vulnerability

Cyclones are among Réunion’s most destructive hazards. They can bring destructive winds, extreme rainfall, storm surge, river flooding, flash floods, landslides, rockfalls, coastal damage, electricity outages, drinking-water disruption, and transport isolation. The 2025 Cyclone Garance event illustrates this risk: Le Monde reported four deaths, wind gusts up to 234 km/h, rainfall exceeding 300 mm in three hours, widespread flooding, infrastructure damage, more than 180,000 homes without electricity, and about 80,000 residents without drinking water. (Le Monde.fr)

Flood risk is amplified by the island’s short, steep watersheds. Heavy rainfall can rapidly generate dangerous runoff in ravines and river channels, overwhelming roads, bridges, drainage systems, and low-lying settlements. French prevention documents repeatedly link Réunion’s historical disaster experience to cyclones, heavy rains, floods, landslides, and rockfalls, while risk-prevention plans for several communes focus specifically on flood and terrain-movement hazards. (Reunion)

3. Landslide, rockfall, and slope-instability vulnerability

Landslides and rockfalls are major risks because Réunion has steep volcanic slopes, deeply eroded valleys, unstable escarpments, intense rainfall, and road corridors cut into difficult terrain. Terrain-movement risk is concentrated along cliffs, ravines, cirques, riverbanks, and high-slope areas, where heavy rainfall and cyclones can trigger slope failures. (DDRM La Réunion)

This creates serious implications for transport connectivity. Roads, bridges, coastal highways, mountain access routes, and settlements in ravines or below unstable slopes may be disrupted by landslides, debris flows, falling rocks, flood debris, and washed-out sections. During Cyclone Garance, landslides, branches, and power cables led to road and bridge closures, while parts of the road network were damaged or washed away. (Le Monde.fr)

4. Coastal erosion, marine submersion, and sea-level-rise vulnerability

Réunion’s coast is exposed to marine submersion, coastal erosion, storm waves, cyclone swell, sea-level rise, and damage to coastal infrastructure. DEAL Réunion materials note that populations and activities are particularly exposed to natural risks including cyclones, floods, coastal erosion or marine submersion, landslides, and volcanic eruptions. (Reunion)

Coastal-risk planning is active in several communes. The official natural-risk portal lists public consultations and risk-prevention plans for coastal hazards, including shoreline retreat and marine submersion, showing that coastal erosion and coastal flooding are recognized land-use planning concerns. (risquesnaturels.re)

5. Volcanic and seismic vulnerability

Réunion’s volcanic risk is dominated by Piton de la Fournaise, one of the world’s most active basaltic shield volcanoes. Volcanic eruptions may generate lava flows, gas emissions, ash, road closures, exclusion zones, tourism disruption, and emergency-management requirements. Le Monde reported that a January 2026 eruption triggered the ORSEC-Volcano emergency plan, with access to the Enclos Fouqué caldera closed for safety. (Le Monde.fr)

Earthquake risk is generally lower than in major plate-boundary countries, but official French risk-prevention materials include seismic risk among Réunion’s major hazards. This means earthquake-safe planning, emergency preparedness, and public awareness remain relevant within the island’s wider multi-hazard framework. (Reunion)

6. Sector-specific vulnerability summary

7. Social vulnerability

The most vulnerable groups include low-income households, people living in flood-prone ravines or coastal zones, residents below unstable slopes, older persons, people with disabilities, isolated mountain communities, households dependent on agriculture or tourism, and communities with limited ability to evacuate or recover quickly. Vulnerability is highest where hazard exposure overlaps with steep terrain, difficult road access, weak housing, limited savings, dependence on single access roads, and repeated exposure to cyclones or floods.

8. Priority resilience needs

Réunion’s resilience agenda should prioritize multi-hazard early warning systems, impact-based cyclone and rainfall forecasting, flood and landslide nowcasting, coastal inundation warnings, slope-risk monitoring, volcanic surveillance, resilient transport corridors, coastal-zone planning, risk-informed land-use regulation, drought preparedness, wildfire prevention, ecosystem-based adaptation, emergency shelter planning, and community-based preparedness.

A practical resilience package should include: