Coastal risk maps may start from a sea level that is too low

What happened

A peer-reviewed review of 385 coastal-hazard studies found that more than 99 percent did not fully align land elevation with the appropriate sea-level reference. Correcting that vertical baseline substantially increased modeled exposure under a hypothetical one-metre rise, especially in parts of the Indo-Pacific.

Why it matters

Adaptation budgets and protection schedules depend on where maps place zero elevation, so a datum mismatch can change which communities and infrastructure appear exposed. The one-metre scenario is a sensitivity test, not a dated forecast, and digital-elevation and local land-motion uncertainties remain.

What to watch

• Use of corrected datasets and the authors' checklist in new coastal assessments.
• Independent reanalysis plus local tide-gauge, elevation, and land-motion validation before plans change.

Sources & evidence

• Sea level much higher than assumed in most coastal hazard assessmentsPeer-reviewed systematic review, Nature (2026), published March 4, 2026. The exposure comparison uses a hypothetical one-metre sea-level rise to test datum alignment; it is not a forecast for a specified year.
• Most studies may underestimate how many people face rising seasIndependent Science News context on the review's methods and implications.

Topics

• Sea-Level Rise
• Coastal Risk
• Adaptation Planning
• Elevation Data
• Risk Mapping