Résumé
The main purpose of this paper is to implement a mathematical model of confinement in a realistic configuration; the model we consider here relies on a previous work by two of the authors in [FR12]. The concept of confinement was introduced by Guelorget and Perthuisot [GP83a] in 1983. It has latter been widely used, studied, discussed and tested (see Guélorget and Perthuisot [GP83b, GP83a], Guélorget, Frisoni and Perthuisot [GFP83], Guélorget et al. [GGLP90], Ibrahim et al. [IGF+85], Debenay, Perthuisot and Colleuil [DPC93], Redois and Debenay [RD96], Barnes [Bar94], Frénod and Goubert [FG07] and Tagliapietra et al. [TSG09]) leading to the conclusion that it is a pertinent parameter controlling the features of living benthic population in paralic ecosystems. Benthic species are species living on the seabed and paralic ecosystems are ecosystems encountered in estuaries, lagoons and closed bays. This is a first motivation to conduct numerical simulations of confinement in a lagoon.