live in a hill or next to it, a lifestyle aside and which requires vigilance

The landslide took place two years ago. At least one ton of stone won out of the hill and shattered on the ground of a courtyard, two meters below. Without doing injuries or big damage. But everything is still fragile. Friable. “It remains scalable, we can still have a similar movement. It is therefore necessary to avoid circulating below regularly ”observes Arthur Blachier, geologist at Caves 37 (1) on site. “I absolutely avoid going therespecifies the owner of the premises. This is just a storage place. »» That he will soon have to get rid of since he has just sold this pretty house of the 19th^e A century located in Luynes, a stone's throw from the city center.

Interventions have tripled in ten years

When he bought it twenty-five years ago, the risk was already present. He lived there, paying attention and without parking a vehicle too close to the hill. He asked Cavings 37 on January 23, 2025 to establish a new diagnosis of the premises as part of this sale. “Most of the activity concerns council to municipalities and diagnostics in individuals, as part of a sale like here”takes up Arthur Blachier. From a visual observation, it detects the compactness of the rock, the appearance of the vegetation and the morphology of the hill.

Sixty interventions of this type take place each year. In 2013, it was three times less. “There are several reasons for this, he added. The union was less known, we were less called. Today, individuals and municipalities are more sensitive to the question. »» The cavity staff 37 have doubled in ten years.

The union has no specific figures to be given on the number of hillsides inhabited or used as cellars and storage places in Indre-et-Loire today. “But we have 110 members and we estimate that 150 the number of cities concerned in the department”indicates the geologist.

Each situation is different. “The approach is obviously not the same if the hill is a troglodyte habitat or a simple cellar. When it is inhabited, we give advice to people but after, as it is a private property, they do what they want ”observes Arthur Blachier. He does not have the memory of housing evacuated as a precaution before a landslide: “There is no warning sign like cracking or other, it suddenly falls. In Charentilly in early January, the house overlooking the hill was evacuated after there were already some signs before. »»

The owner of the house of Luynes has the memory “From a friend who lives in a troglodyte house in Saint-Étienne-de-Chigny. One evening, he found two tonnes of stone on his bed. »» A stroke of luck. “Fifteen years ago, 10 ^M3 fell into one of the cavities here, he resumes. It made a big boom, a bit like a plane that passes the sound wall. »»

Climate change in question

Since then, everything has been frozen. “The cavities are confined spaces and the evolution is very slow compared to a rocky front. It can put decades before evolving again ”observes Arthur Blachier. Does climate change change the situation? “Yes, because there is a direct relationship between the weather, the climate and the claimsreplies the geologist. It is water that triggers ground movements. It infiltrates and in Touraine, the tuffeau is a porous rock. The water interferes in the voids and the mechanical resistance collapses. »»

It is advisable to cut the vegetation that lives above the cellars. But not to remove everything. Pivoting root plants infiltrate the rock, but there are suitable plants “With horizontal roots that limit streams and infiltration”completes Arthur Blachier. Finally, there is the possibility of consolidating the hills with fences anchored to the rocky massif. “To secure four cavities, it would have been necessary to invest € 15,000. But with lost funds, because it does not change the value of the house ”blows the owner of Luynes.

(1) Intercommunal union in charge of the census and preservation of underground cavities and rocky cliffs of Indre-et-Loire.