A numerical approach to study hydrodynamics and morphological evolution of a lagoon inlet  <B>A numerical approach to study hydrodynamics and morphological evolution of a lagoon inlet</B><P>L. D'Alpaos (*), A. Defina (*), B. Matticchio (+), P. Ruol (**), M. Sclavo (**)</B><I><P> (*) University of Padova, Istituto di Idraulica, Via Loredan, 20 35131 Padova Italy. tel:+39 49 8275428 ; fax:+39 49 8275446 <BR> (**) University of Padova, Istituto di Costruzioni Marittime, Via Ognissanti, 39 35139 Padova Italy. tel:+39 49 8071299; fax:+39 49 8073467 <BR> (+) Ipros Ingegneria Ambientale, Corso del Popolo, 8 35100 Padova Italy. tel:+39 49 660647; fax:+39 49 660311</I><P> Abstract<P> In this paper a methodology for studying the complex situation represented by lagoon inlets is suggested. The outer conditions must be defined starting from the offshore wave conditions and can be based on the use of a suitable mathematical model able to propagating the deep water waves to the coastal zone. Such model (known as HISWA) includes generative and dissipative effects due to winds and currents, bottom friction (that is of great importance in such studies) and wave breaking. After propagating waves to shallow waters it is possible to evaluate wavedriven forces and bottom velocities in the zone close to the lagoon inlets. The current field inside the lagoon and close to the inlets is computed separately through a 2D finite element mathematical model that solves the vertically integrated momentum and continuity equations for shallow free surface flows taking into account the wavedriven forces calculated by HISWA. The paper also presents an application of the described methodology to a real field case concerning the Barbamarco lagoon in the Po river delta, Italy.<P>