Clay shrink-swell subsidence
Ground movement peril linked to moisture variation in clay soils, a growing loss source worsened by climate change.
Clay shrink-swell subsidence is a ground movement phenomenon caused by moisture variation in clay soils: during drought the clay shrinks; when rain returns it swells. These differential movements crack the foundations and structures of buildings, especially detached houses on sensitive soils. In France, this peril is covered under the natural catastrophe regime once a decree recognizes the state of catastrophe for geotechnical drought. Climate change, by intensifying the alternation of droughts and rainfall, structurally worsens this risk, which has become one of the most dynamic and costly loss items of the regime. For insurance and reinsurance, clay subsidence illustrates the drift of a so-called secondary peril into a major burden, posing challenges of reserving, prevention and sustainability of the pooling regime.
Textbook case: a detached house on clay soil can suffer structural cracks after an intense drought, a loss covered under the French natural catastrophe regime.
clay subsidence, clay shrink-swell, drought subsidence, CatNat drought
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