Chaigneau Alexis, Okpeitcha O. V., Morel Y., Stieglitz Thomas, Assogba A., Benoist Morgane, Allamel Pierre, Honfo J., Sakpak T. D. A., Retif F., Duhaut T., Peugeot Christophe, Sohou Z. (2022). From seasonal flood pulse to seiche : multi-frequency water-level fluctuations in a large shallow tropical lagoon (Nokouacutee Lagoon, Benin). Estuarine Coastal and Shelf Science, 267, p. 107767 [12 p.]. ISSN 0272-7714.
Titre du document
From seasonal flood pulse to seiche : multi-frequency water-level fluctuations in a large shallow tropical lagoon (Nokouacutee Lagoon, Benin)
Année de publication
2022
Auteurs
Chaigneau Alexis, Okpeitcha O. V., Morel Y., Stieglitz Thomas, Assogba A., Benoist Morgane, Allamel Pierre, Honfo J., Sakpak T. D. A., Retif F., Duhaut T., Peugeot Christophe, Sohou Z.
Source
Estuarine Coastal and Shelf Science, 2022,
267, p. 107767 [12 p.] ISSN 0272-7714
This study investigated the main water-level (WL) variability modes of Nokoué Lagoon in Benin (West-Africa). The average WL ranges between 1.3 and 2.3 m between the low-and high-water seasons. Seasonal as well as weak interannual variations between 2018 and 2019 are driven by rainfall regime over the catchment and associated river inflow. At sub-monthly scales, the lagoon is tidally choked: ocean tides can reach 90 cm, whereas in the lagoon semi-diurnal and diurnal tides hardly reach few centimeters. Choking conditions vary with river inflow and ocean tide amplitude, correctly represented by a simple tidal choking model. Diurnal modulation and asymmetry of the tide are stronger (weaker) during high (low) water period. We also observed WL variations of +/- 5-10 cm at a fortnightly frequency, stronger during wet (high-water) season. Superimposed on the seasonal, fortnightly and tidal WL variations, we further observed short-term high-frequency seiche events. Mostly observed during dry (low-water) conditions, they are characterized by typical standing-wave oscillations of 5-10 cm amplitudes and 3 h periods. They are forced by the passage of fast-moving squall-lines that induce strong wind variations, heavy rainfalls and rapid drop-off of the air temperature. Results obtained in this study provide useful metrics for the validation of flood forecasting models to be implemented in Benin, and elsewhere on the West African coastline.
Plan de classement
Sciences du milieu [021]
;
Limnologie physique / Océanographie physique [032]
;
Hydrologie [062]
Description Géographique
BENIN ; GOLFE DE GUINEE ; ZONE TROPICALE ; NOKOUE LAC
Localisation
Fonds IRD [F B010087433]
Identifiant IRD
fdi:010087433
