5760 20220406171011.0 CTALK-2022-0056 Van Camp, M. Extreme hydrometeorological events, a challenge for geodesy and seismology networks 2022 2022-05-23 The use of seismometer and gravimeter captures complementary data and brings a new understanding of the July 2021 catastrophic floods in Belgium. A sudden increase in seismic noise coincides with the testimony reporting on a “tsunami” downstream of the Membach geophysical station, along the Vesdre valley. Concurrently, the gravimeter evidenced a rising saturation of the weathered zone, thus showing less and less water accumulation. When rain re-intensified after a 3-hour break, the saturated state of the subsoil induced an accelerated increase of the runoff, as revealed by the Vesdre River flow, in a much stronger way than during the rainy episodes just before. We show that a gravimeter can detect in real-time the saturation of the catchment subsoil and soil. This saturation resulted, when the rain re-intensified, in a sudden, devastating and deadly flood. This opens perspectives to use real-time gravity for early warnings of such events NO Membach Superconducting gravimeter Flash Flood July 2021 Vesdre Valley Seismic network Hydrogeology de Viron, O. Dassargues, A. Delobbe, L. Chanard, K. Gobron, K. EGU General Assembly michel.vancamp@observatoire.be Contributed CTALKCONT