Timescales of emergence of chronic nuisance flooding in the major economic centre of Guadeloupe

Chronic flooding, occurring at high tides under calm weather conditions, is occasionally taking place today in the low-lying areas of the Petit-Cul-de-sac marin (Guadeloupe, West Indies, French Antilles). This area includes critical industrial, harbor and major economic infrastructures for the island. As sea level rises, concerns are growing regarding the possibility for repeated chronic flooding events, which would alter the operations at these critical coastal infrastructures without appropriate adaptation. Here, we use information on past and future sea levels, vertical ground motion and tides to assess times of emergence of chronic flooding in the Petit-Cul-de-sac marin. For RCP8.5 (i.e., continued growth of greenhouse gas emissions), the number of flood days is projected to increase rapidly after the emergence of the process, so that coastal sites will be flooded every two days within 2 decades after the onset of chronic flooding. For coastal locations with the smallest altitude, we show that the reconstructed number of floods are consistent with observations known from a previous survey. One key uncertainty of our result is the actual rate of subsidence of the island. However, our satellite interferometric synthetic-aperture radar results show that the local variability of this subsidence is smaller than the uncertainties of the technique, which we estimate between 1 (standard deviation of measurements) and 5mm/yr (upper theoretical bound). Our results imply that adaptation pathways considering a rapid increase of recurrent chronic flooding are required in the critical port, industrial and commercial center of Guadeloupe, as well as presumably in many low-elevation coastal zones of other tropical islands.

G. Le Cozannet, I. Déborah, M. de Michele, Y. Legendre, M. Moisan, R. Pedreros, R. Thiéblemont, G. Spada, D. Raucoules, Y. de la Torre - NHESS

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tide gauge data. (a) time series of raw data (black: raw cleaned data, red: data removed from the analysis, and  corresponding to the cyclones, identified with blue lines). (b) distribution of daily maxima, after the water level data post510 processing described in section 3.3 (cyclone removed, year and day filtering, detrended sea-level rise).
Tide gauge data. (a) time series of raw data (black: raw cleaned data, red: data removed from the analysis, and corresponding to the cyclones, identified with blue lines). (b) distribution of daily maxima, after the water level data post510 processing described in section 3.3 (cyclone removed, year and day filtering, detrended sea-level rise).