Photo: Henk Monster · CC BY 3.0100% of Calvisson’s residents live on shrink-swell clay
What the state records for Calvisson: natural-disaster declarations since 1982, risk plans, mapped flood zones, clay ground, earthquake zone, radon and industrial sites. Hazard risk is not graded in France: there is no national flood map, so a town outside the mapped areas can’t be called safe from floods.
6 hazards in Calvisson at a glance
Bars show where the town sits among French towns of 2,500+; they are not a grade. Disaster declarations are shown, not compared.
Flood zones
Disasters declared
Clay ground
Earthquakes
Radon
Industrial sites
Why hazards aren’t graded in France
In the UK, the Hazard risk grade is the share of homes in a mapped flood zone; in the U.S., it is FEMA’s modelled yearly damage to buildings. Both rest on maps that cover the whole country. France maps flood zones in detail only in its 125 areas at highest risk (TRI), so most towns have no figure, and a blank would read as “dry”. The state’s disaster declarations don’t fill the gap: they depend on the mayor applying, and they don’t line up with the mapped zones. So Calvisson has no Hazard grade, and its overall grade uses the other six subjects.
Everything on this page is shown as published. We’ll grade it when France publishes a national flood map.
Flood zones in Calvisson on the map
The state’s own layers from Géorisques, drawn over the street map. Tap a layer to switch it on or off.
Flood zones are drawn only inside the state’s mapped areas (TRI, pink outline). Outside them, the map is blank because nobody has drawn it, not because the ground is dry.
0.2% of Calvisson’s residents live in a mapped flood zone
Residents in the state’s medium-probability flood zones, by where the water comes from. Mapped areas only.
Share of residents in a medium-probability flood zone. Calvisson has more than 32% of mapped towns. The other 2,833 towns of 2,500+ have no detailed map.
| # | Town | People | In a flood zone | |
|---|---|---|---|---|
| 1 | Estaires Nord | 6,525 | 0% | |
| 2 | Bon-Encontre Lot-et-Garonne | 6,530 | 0% | |
| 3 | Bonsecours Seine-Maritime | 6,442 | 0% | |
| … | ||||
| 11 | La Montagne Loire-Atlantique | 6,505 | 0.2% | |
| 12 | Grézieu-la-Varenne Rhône | 6,472 | 0.2% | |
| 13 | Calvisson Gard | 6,486 | 0.2% | |
| 14 | Vezin-le-Coquet Ille-et-Vilaine | 6,471 | 0.3% | |
| 15 | Saint-Priest-en-Jarez Loire | 6,471 | 0.3% | |
| … | ||||
| 40 | Marignier Haute-Savoie | 6,507 | 22% | |
| 41 | Longué-Jumelles Maine-et-Loire | 6,564 | 23% | |
Mapped area: – (flood directive maps, 2nd cycle, 2020). Medium probability is roughly the 1-in-100-year flood. Residents placed by INSEE’s 200 m income grid (2021).
26 natural disasters declared in Calvisson since 1982, 13 for floods
The state’s register of natural-disaster orders, 1982 to January 2026.
- 2023Drought: clay subsidenceMarch 31, 2023 – June 29, 2023 · order published August 2, 2024
- 2022Drought: clay subsidenceJuly 1, 2022 – September 30, 2022 · order published September 26, 2023
- 2021Floods and mudflowsSeptember 14–16, 2021 · order published September 26, 2021
- 2019Drought: clay subsidenceApril 1, 2019 – December 31, 2019 · order published July 10, 2020
- 2018Drought: clay subsidenceJanuary 1, 2018 – March 31, 2018 · order published August 9, 2019
- 2017Drought: clay subsidenceJuly 1, 2017 – September 30, 2017 · order published July 5, 2018
Show all 24 events
- 2016Drought: clay subsidenceJanuary 1, 2016 – December 31, 2016 · order published September 1, 2017
- 2015Floods and mudflowsAugust 23, 2015 · order published January 22, 2016
- 2014Floods and mudflowsOctober 9–11, 2014 · order published December 7, 2014
- 2014Floods and mudflowsSeptember 29, 2014 · order published November 7, 2014
- 2012Drought: clay subsidenceJanuary 1, 2012 – December 31, 2012 · order published August 2, 2013
- 2007Drought: clay subsidenceJanuary 1, 2007 – March 31, 2007 · order published August 13, 2008
- 2005Floods and mudflowsSeptember 6–8, 2005 · order published October 14, 2005
- 2002Floods and mudflowsSeptember 8–10, 2002 · order published September 20, 2002
- 2001Floods and mudflowsOctober 6–7, 2001 · order published February 9, 2002
- 1998Floods and mudflowsSeptember 4, 1998 · order published December 11, 1998
- 1998Drought: clay subsidenceMarch 1–31, 1998 · order published June 6, 2001
- 1995Floods and mudflowsOctober 13–15, 1995 · order published January 7, 1996
- 1994Floods and mudflowsOctober 19–21, 1994 · order published March 17, 1995
- 1993Drought: clay subsidenceSeptember 1, 1993 – December 31, 1997 · order published July 29, 1998
- 1992Floods and mudflowsSeptember 21–23, 1992 · order published November 18, 1992
- 1989Drought: clay subsidenceMay 1, 1989 – August 31, 1993 · order published November 24, 1994
- 1988Landslide · Floods and mudflowsOctober 3, 1988 · order published October 8, 1988
- 1982Floods and mudflows · StormNovember 6–10, 1982 · order published November 19, 1982
Declarations by hazard · 1982–2025
Each line is a state order recognizing a natural disaster in the commune (“CatNat”), which lets insured owners claim. The latest flood began September 14, 2021; 9 flood declarations since 1995.
This count partly reflects how often a mayor applies for a declaration, so it isn’t compared between towns. It is a record of recognized claims, not a flood map. Source: GASPAR, Géorisques, file of 5 October 2026 (orders published to January 2026).
The state lists 7 hazards for Calvisson
Risk plans in force or in preparation, and the prefecture’s list of major risks.
| Hazard | Risk plan (PPR) | Listed by the prefecture |
|---|---|---|
| River flooding and runoff | Approved 2017 | ✓ |
| Landslides and rockfalls | — | ✓ |
| Clay shrink-swell | — | ✓ |
| Earthquake | — | ✓ |
| Forest fire | — | ✓ |
| Radon | — | ✓ |
| Dangerous goods in transit | — | ✓ |
A risk plan (plan de prévention des risques, PPR) is the state’s map of where building is banned or restricted because of a hazard; it is attached to the town’s planning rules, and a seller or landlord must tell you if the home is in one. The prefecture’s file of major risks (DDRM) lists the hazards it expects in each commune.
Plans: PPRN-I - Calvisson
Earthquake zone 2 (low); 100% of residents on shrink-swell clay
What the ground under Calvisson does: national maps, the same for every town.
Residents on shrink-swell clay · share of residents
Clay ground swells when wet and shrinks in drought, which cracks walls of houses on shallow foundations. Since 2020, a soil study is required before selling a building plot in a medium or high zone. 11 drought (clay) declarations here since 1982.
Calvisson is in zone 2 (low). New buildings must follow the earthquake building code (Eurocode 8) for their type. The zone sets building rules; it isn’t a forecast.
Clay: BRGM shrink-swell exposure map 2025, residents placed by INSEE’s 200 m grid. Earthquakes: national seismic zoning, decree of 22 October 2010.
Radon potential in Calvisson: category 1 of 3 (low)
Radon is a natural radioactive gas from granite and volcanic rock; it builds up indoors.
Calvisson is in category 1, the lowest: the rocks here release little radon.
The category describes the rocks under the commune, not any home: a test is the only way to know.
Source: radon potential by commune, IRSN (now ASNR), 2019.
No industrial risk plan reaches Calvisson
Hazardous sites whose danger zone reaches the town, and the technological risks the prefecture lists.
| Dangerous goods in transit | road, rail, pipeline or waterway through the town |
Seveso sites store or use large amounts of dangerous substances; upper-tier sites have a risk plan around them. Distances are from the town’s center.
Sources: GASPAR (PPRT, DDRM), Géorisques, 5 October 2026; Seveso sites from Géorisques’ register of classified installations.
Hazards in Calvisson’s neighbors
Towns of 2,500+ within 30 km. Tap one to open its hazards page.
* Share of residents in a mapped medium-probability flood zone; a dash means no detailed map, not no risk. Radon: category 1 to 3.
Being ready in Calvisson
Where France publishes warnings, and what to ask before you buy or rent.
- Météo-France’s vigilance map gives the day’s warnings by département, from yellow to red.
- Vigicrues shows river levels and flood warnings for the main rivers, updated twice a day.
- FR-Alert sends emergency alerts to every phone in the area; no sign-up needed.
- The seller or landlord must give you a risk statement (état des risques) for the address, listing the plans it is in.
- They must also tell you about any natural-disaster claim paid on the home.
- Géorisques gives the same statement for any address, free.
- Don’t drive or walk through floodwater.
- Go upstairs, not to the cellar or car park.
- Call 112 if you’re in danger.
- Ask for the risk statement and read which plans the address is in.
- Ask the town hall for its risk booklet (DICRIM) and safety plan (PCS).
- For a house, look for cracks and ask about the foundations: much of the town is on shrink-swell clay.
- Check that home insurance includes natural-disaster cover (it comes with fire cover).
What this data can and can’t tell you
- Not graded. France has no national flood map, so we don’t grade hazard risk. Comparisons on this page are with other French towns of 2,500+, shown for context.
- Mapped areas only. Flood shares exist only where the state has mapped flooding in detail (the TRI areas). A town without a figure has no map, not no risk.
- Disaster declarations. A CatNat order recognizes a disaster so that insurers pay; it follows the commune’s application. The count partly reflects how often a mayor applies, so we show it but don’t compare towns on it.
- Plans. A risk plan maps where building is limited; it doesn’t say any one home will flood.
- Clay, earthquakes, radon. National maps of the ground: they describe susceptibility and set building rules, not damage or forecasts.
Questions about hazards in Calvisson
Does Calvisson flood?
The state has declared 13 flood disasters in Calvisson since 1982, the last starting September 14, 2021. On the state’s detailed map, 0.2% of residents live in a medium-probability flood zone. A flood risk plan is in force.
Is Calvisson at risk of earthquakes?
Calvisson is in seismic zone 2 of 5 (low). The zone sets building rules for new construction; it isn’t a forecast.
Is there radon in Calvisson?
Radon potential is category 1 of 3 (low). It describes the ground under the commune; only a test tells you a home’s level.
Are there dangerous industrial sites near Calvisson?
No industrial risk plan reaches Calvisson; 0 Seveso sites lie within 5 km.
Why doesn’t Calvisson have a Hazard grade?
France maps flood zones in detail only in its areas at highest risk, so most towns would have no figure, and a blank would look like no risk. We show the data instead, and will grade it if France publishes a national flood map.
Sources: Géorisques (Ministry of Ecological Transition), GASPAR file of 5 October 2026: CatNat orders, risk plans (PPRN, PPRT, PPRM), flood atlases, DDRM, DICRIM · flood directive maps, 2020 (TRI 2nd cycle) and 2024 outlines · BRGM clay shrink-swell map 2025 · seismic zoning, decree of 22 October 2010 · ASNR (formerly IRSN) radon potential 2019 · INSEE 200 m income grid 2021 (where residents live) · map: Géorisques layers over © OpenStreetMap contributors · Seveso sites: Géorisques register of classified installations. Licence Ouverte / Open Licence (Etalab). Not graded.
Contains public sector information under the Licence Ouverte / Open Licence 2.0 (Etalab): INSEE, DGFiP, the Interior Ministry’s statistics service (SSMSI), the Ministry of Education (DEPP), the Health Ministry’s statistics service (DREES) and the Housing Ministry (Carte des loyers). Commune boundaries: IGN Admin Express.