Flood Wave Speed Measurement Using a Seismic Network in la Reunion Island
Abstract
La Réunion Island, located in the western Indian Ocean, undergoes heavy annual precipitations, particularly during the rainy season (Dec. to Apr.) during tropical storms and cyclones. Large rainfalls (up to 10 m in the eastern part of the island) that affect this volcanic island strongly impact erosions processes and streams morphodynamics. Recordings from five seismic stations of a temporary seismic network (https://doi.org/10.15778/RESIF.ZF2015) installed along the Rivière des Pluies, a river located in the northern part of La Réunion Island, were analysed to characterize high-frequency (> 1 Hz) seismic signals associated with the river activity during the tropical cyclone Dumazile (March, 2018). This river is 18 kilometer-long, with a slope ranging between 3 and 7 %, and its watershed surface is 46 km2. A very good correlation (r2 ~ 0.9) is evidenced between the root mean square (RMS) of the seismic wave amplitude at each station and the hydrographs. Moreover, we demonstrate a very good correlation between the RMS of the recordings of each station installed ~1.5 km apart.
The flood event produced by the cyclone comprises several flood peaks. Considering individual peaks of the hydrograph, we observe a clear delay from one station to another. We used the RMS as a proxy of the hydrograph and compared the peaks delays to measure the speed of the flood wave migrating from upstream to downstream during the two cyclones. During Dumazile, the mean flood wave speed is 5.7 m/s. The observation of a flood wave on such a small basin suggests a quite strong and localized area of precipitation upstream during some particular active period of the cyclone. Such seismic monitoring of a river activity during a cyclone is therefore a powerful tool to characterize the spatial variability in the precipitations and offers very interesting operational perspectives for flood wave survey during cyclonic events.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S33B..07G
- Keywords:
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- 0799 General or miscellaneous;
- CRYOSPHERE;
- 9810 New fields (not classifiable under other headings);
- GENERAL OR MISCELLANEOUS;
- 1895 Instruments and techniques: monitoring;
- HYDROLOGY;
- 7299 General or miscellaneous;
- SEISMOLOGY