Ingrid Girardeau and Manuel Parizot, respectively BRGM Regional Director and Acting Regional Director in Réunion and Mayotte, are in charge of assignments to support public policies and research projects, particularly with respect to water, natural hazards, geothermal energy and mineral resources. Their teams provided invaluable support to the local authorities during cyclones Chido and Garance last winter.
How is BRGM involved in cyclone-risk prevention?
Ingrid Girardeau - On Reunion Island, as in Mayotte, BRGM produces natural hazard maps, particularly of landslides and coastal flooding. These documents help public authorities to regulate urban development in the most exposed areas, through natural-hazard prevention plans.
Manuel Parizot - Indeed, cyclones, depending on their intensity, cause landslides, flooding, bank retreat or even coastal flooding. It is therefore important to limit the exposure of property and people to these hazards.
Storms with colossal impacts
After cyclone Garance hit Réunion, BRGM teams carried out more than 130 geological risk assessments on homes, as seen here in the Butor ravine.
© BRGM
What was your role during the cyclone crises at the end of 2024 and beginning of 2025 ?
I. G. - During each hurricane season, i.e. from November to May, we are on-call to carry out emergency diagnostics of geological risks, particularly on roads. We are also involved in the prefecture's cyclone crisis management procedures, working alongside DEAL Réunion to appraise ground movements and the risk they can pose to homes. It is on the basis of our reports that the authorities issue evacuation orders and prohibit accessto certain areas. After Garance, we had to bring in colleagues from mainland France to help us with this assessment, while others were mobilised to validate our deliverables, which can have major consequences for the population and for which BRGM may be held liable.
M. P. - Mayotte, which hasn't suffered such a devastating cyclone for a century, doesn't have the same risk culture when it comes to this type of event. Faced with the immediate consequences, the first priority was to re-establish basic services, especially as another storm, Dikélédi, hit the island on the following 10th January! We were therefore called in to carry out field surveys just two month after Chido ! It should also be noted that our reports contain longer-term recommendations for mitigating the risks associated with cyclones, mainly in terms of studies to be carried out.
Are you still involved once the crisis is over ?
I. G. - Yes, if the local authorities need us. In particular, we participate in public meetings to explain to residents the risks involved and the need to evacuate homes, such as those built illegally at the bottom of ravines. We are also asked to attest the state of ‘natural disaster’ in the municipalities concerned. We may also accompany official visits by government representatives who have come to observe the damage on site.
M. P. - For our part, we were consulted on the drafting of the Act for the reconstruction of the island. And we are at the disposal of the authorities to implement this ambitious programme, which aims to make Mayotte a sustainable and resilient island.
Issue No.1 of BRGM mag, BRGM's magazine, was published in November 2025.
© BRGM
BRGM mag n°1 : The subsoil, a key to the future of territories
BRGM launches BRGM mag. This new magazine for the general public aims to explain why the subsurface is so vitally important and the essential contribution made by the French geological survey in responding to today's main environmental, energy and sovereignty concerns.
Borrowing from journalistic codes, BRGM mag has adopted a deliberately flexible range of features, to be able to adapt to its latest news, with varied forms (articles, interviews, computer graphics, reports, FAQs, etc.), as well as a popularised and educational editorial style to make the information accessible to as many people as possible.
This first issue examines the increasingly central role of the subsurface in land use planning and ecological transition. Because an essential part of our future is playing out beneath our feet.
