New BREACH-METHOD refines flood risk projection for the Netherlands

A new study reveals that the Netherlands’ standard flood risk method may be overstating how often dikes will fail—and by how much. The long-standing Delta Programme Safety (DPV) approach treats each dyke segment in isolation, assumes no coordinated emergency response and ignores how one breach can ease pressure elsewhere. Those limits can inflate projected flood frequencies, drive up insurance costs, discourage investors and depress property values in flood-prone areas.

Researchers have now introduced the BREACH-METHOD, which blends historical breach data with expert judgement to deliver a more nuanced picture. Instead of treating every dike as a lone actor, the framework groups modeled storm scenarios into nine probability bands—from everyday surges to once-in-a-millennium events. Specialists then estimate how many breaches (zero, one or multiple) each band might produce, creating a comprehensive “event set” of possible floods, that reflects real-world system interactions and emergency measures.

When applied to the Dutch Delta, BREACH cuts estimated flood chances sharply. Under today’s climate it lowers national flood probability from about one-in-three years (with DPV) to roughly one-in fifty years. In parts of the Rhine, Lake IJssel, and tidal zones it can cut risk by more than 40 times. For banks, insurers, investors, and planners, this means more accurate stress tests, better pricing of flood cover, and smarter decisions on where—and how much—to build or insure.