Overview

• HYDROS 25 runs October 13–17 with the first FR‑Alert broadcast completed in La Ferté‑Gaucher and wider zone tests set for October 15 in Essonne, Seine‑Saint‑Denis, Val‑de‑Marne, and Paris’s Beaugrenelle neighborhood.
• FR‑Alert sends a loud notification that overrides silent mode displaying an “Alerte inondation” test message stating no action is required, with authorities urging residents not to call emergency services and to answer a feedback questionnaire.
• The operation marks the first real‑condition use of the national cell‑broadcast system in Île‑de‑France to verify the alert chain and the ability to reach people quickly in a flood situation.
• On‑the‑ground simulations include volunteer evacuations, crisis‑cell exercises, temporary reception areas, and infrastructure protection such as the RATP installing a batardeau at Métro Rome near Saint‑Lazare.
• Officials outline potential impacts of a major Seine flood with about 630,000 people directly in flood zones, widespread service disruptions to power, heat, water, and transport, and possible costs up to €30 billion.