Land subsidence
How Darwin prices the damage a site suffers as the ground beneath it slowly sinks where groundwater is overdrawn.
Land subsidence
Where groundwater is pumped faster than it recharges, the ground beneath it compacts and slowly sinks. Uneven sinking distorts and cracks structures over the years. Subsidence is a slow creep, distinct from clay shrink-swell. It prices both Property damage (% of asset value) and Business interruption (% of annual revenue).
What the map shows
- Today: the Herrera-García global subsidence susceptibility for 2010, in six classes from very low to very high (sheet).
- Projected: none. Subsidence is driven by groundwater use, not by a climate variable, so no scenario moves it and the figure is the same at every horizon.
How the loss is computed
The engine reads the susceptibility class at the site's point. A class-to-loss table, scaled by the ground vulnerability of the site type, gives the damage state the ground eventually reaches. Because creep has a speed rather than an occurrence, that damage is spread over the time it takes to appear, which gives an annual loss. That rate of accrual is measured on Copernicus EGMS satellite ground motion, converted to structural damage on the Boscardin & Cording angular-distortion thresholds. Business interruption is a loss-of-use relation on the ground loss. The hazard is tagged Proposal. See Damage functions: The geotechnical trio and Climate risks.
Subsidence is measured as a slow drift: the Exclude slow-drift baselines switch sets its baseline to zero. With no projection, its figure then reads zero at every horizon.
Sources
- Herrera-García et al. (2021), "Mapping the global threat of land subsidence", Science; Global Subsidence Maps (figshare). Licence not confirmed.
- Rate of accrual: Copernicus European Ground Motion Service (EGMS), cross-checked against the French retrait-gonflement insurance claim record. EGMS: Licence not confirmed.
Limits
- A screening layer, not a siting tool.
- The rate of accrual is measured on two European basins and is not yet validated on the faster-sinking basins of Southeast Asia and the Americas.
- The class ramp is under review: within an aquifer being drawn down, the classes separate about six times less steeply than the posed table.
- The layer predicts groundwater-overdraft subsidence only, so it carries no signal where that process does not run.