The Oued Mellah is the seasonal river that empties into the Atlantic just west of Mohammedia. In late spring its small estuary becomes a marsh full of migratory waterbirds — flamingos, spoonbills, herons, and the occasional black-winged stilt — making it one of the better-known birding spots within easy reach of Casablanca.
Access is on foot from the coast road that crosses the river on a low concrete bridge. There is no formal trail, but the marsh is easy to skirt along the dunes on either side. Bring binoculars; the birds keep their distance and the light off the salt flats can be punishing in summer.