Abstract: For 40 years now, the swing of the economic activities of the country from the inside to the outside has been going on at a speedy pace. Yet, in view of this growing and continued pressure, Moroccan coastline represents a fragile and instable physical space, which enjoys neither protection nor development.

Therefore, the need is growing, first to ensure the maintenance and the stabilization of the coastline, and, on the other hand, to study and be prepared for phenomena that risk harming its role and/or its development.

Sidi Moussa lagoon (Moroccan Atlantic coast) is part of an inter-dunal fissure of the oceanic territory protected by a baymouth bar of consolidated dunes made of bio-calcarenite from the plio-quaternary age. The lagoon lays on a area of 4.2 sq km. It is located in a region placed at the semi-arid tier. The lagoon is part of the Moroccan sites that are classified as humid zones of national importance for the conservation of birds within the framework of the Ramsar convention. The lagoon of Sidi Moussa is known also for its importance in terms of the safeguard of rare birds.

With the goal of understanding the mechanisms of the morphogenesis, and of analyzing the morpho-dynamic variations of the split and the sandpit of the Sidi Moussa lagoon, we have suggested an alimetric analysis of the beach profiles, and the evolution of the sandpit and the split of the lagoon between 1949 and 1997 was re-formed by using multi-date air photos (1949, 1984, 1987 and 1997).

The findings of the evolution study of the split and the sandpit show that the evolution is quite slow. It is not clear whether this evolution could have a tendency towards a more or less large sanding up and a development of the split, which could trigger the partial closure of the lagoon and hence the reduction of the lagoon-ocean exchanges.

Key works:

Sidi Moussa lagoon, split, sandpit, altimetric profiles, diachronic, multi-date air photos.