Seismic signature of a river flooding in La Réunion Island during the tropical cyclone Dumazile (March 2018)

Abstract

Monitoring of sediment transport during extreme flood events is difficult and often impossible. Fluvial seismology can provide constraints on the mechanisms of this transport and on the seismic sources but few cases of application in context of extreme events such as tropical cyclones were realized. Recordings from three seismic stations temporarily installed along a river (the Rivière du Mât) located in La Réunion Island (Indian Ocean) are analysed to characterize high-frequency (> 1 Hz) seismic noise induced by the extreme flood generated by the tropical cyclone Dumazile (March 2018). We evidence a good correlation (r2 = 0.94) between the amplitude of the seismic signal and the water level at lower frequencies (2–7 Hz), particularly during the rising limb of the river flood. The relationship between seismic amplitude and water level measurements tested at multiple frequency ranges are consistent with a signal dominated by water flow at lower frequencies and by sediment transport at higher frequencies (15–45 Hz). We show that the use of seismic measurement, particularly at stations located very close to the riverbed can provide comprehensive information on the mechanisms involved during sediment transport associated with extreme flood events when direct measurements are not possible.