Marine Flooding Risk (France, BRGM)

Source: BRGM (Sea Level Rise) Year: 2016 Category: Physical risks · Mitigating services · Climate Acute Risks Coverage: Region (France) Format: Boundary polygons Used in risk analysis: No (contextual layer; not used in materiality scoring)

What it shows

This layer outlines French coastal areas potentially exposed to marine flooding during severe storm events combined with high tide. It is intended for screening and strategic assessment: identifying which sites sit in low-lying coastal zones that could be inundated under elevated sea levels. It is indicative and non-regulatory, so it signals potential exposure rather than a legally defined flood zone.

How it is built

The layer is drawn from BRGM's sea-level-rise exposure mapping for France. Exposure is delineated by assuming a water level of +1.5 m relative to 2016. This elevation is chosen to approximate the combined effect of high tide and storm surge during severe storms, a magnitude consistent with surges observed on European coasts. Areas lying below this water level are mapped as potentially exposed, producing polygons of coastal flood exposure for screening.

How to read it

This is an exposure footprint rather than a graded score. A site that falls within a mapped polygon is flagged as potentially exposed to marine flooding under the +1.5 m scenario; a site outside the polygons is not flagged at that threshold. Because the layer is indicative and non-regulatory, it should inform screening and prioritisation, not regulatory or insurance decisions.

Class thresholds

The underlying quantity is a physical variable: marine water level during a severe storm combined with high tide, in metres relative to the 2016 sea level (m). The layer is delivered as a single binary exposure mask rather than a graded set of risk classes: it has only one class — potentially exposed — symbolised with a single static fill colour. Every polygon marks land that lies below the modelled storm-plus-tide water level; the absence of a polygon means the location sits above it.

The single physical threshold that defines the mask is +1.5 m relative to 2016, chosen to approximate the combined effect of high tide and storm surge during severe storms, a magnitude consistent with surges observed on European coasts. There is no further risk-flag threshold inside the layer: this is a contextual layer, not used in materiality scoring, and the TOML defines no proximity trigger; the trigger is simply falling within the +1.5 m exposure footprint.

How these thresholds were set. The +1.5 m water level and the resulting exposure footprint are defined by BRGM's Sea Level Rise exposure mapping for France; the choice of that elevation to represent a severe storm-surge-plus-tide event is set in the BRGM methodology and is not a Darwin-derived classification. Darwin uses the resulting footprint directly as a coastal-flood exposure mask.

Reference: BRGM — Sea Level Rise, France (sealevelrise.brgm.fr).

Source

BRGM — Sea Level Rise exposure maps (France), marine flooding delineated at +1.5 m relative to 2016.

Comparison with the WWF Risk Filter Suite

This is a French regional dataset with no global equivalent in the WWF Risk Filter Suite. It sits among Darwin's additional physical-hazard layers that extend beyond the WWF set; WWF expresses flooding at basin level globally, whereas this layer provides a localised national coastal-flood exposure footprint that WWF does not publish.

Generated from darwin/layers/layer-marine-flooding-risk-france-brgm.toml and risk_indicator_pairs.toml (develop).