The present work analyzes the bed mobility in the outer area of the estuary of Piedras River by observing
the changes of morphology, dimensions and orientation of bedforms by means of the use of technical of
Side-Scan Sonar. This coastal system is a small and narrow estuary, with a reduced fluvial input that
develops a wide littoral spit in its mouth in whose apex a wide ebb-tidal delta is developed. On the back
area of the deltas flood and ebb tidal currents develop a variety of sandy bedforms. The comparison of
flood and ebb forms allows analyze the hydrodynamic regime and the sand mobility due to the action of
the main currents