Towards enhancing tidally-induced water renewal in coastal lagoons

Abstract

In order to address the problem of limited water renewal in restricted lagoons of moderate size having at least two tidal inlets, a method is proposed to enhance water exchange between the lagoon and the open sea. The method consists of altering either the amplitude or the phase of the tide in one of the inlets. It is shown in the paper that this will result in an alteration of the function of the lagoon, from a lagoon periodically exchanging water equal to a tidal prism within each tidal cycle with the adjacent water body, towards an effectively flow through system, substantially improving the flushing rate of the lagoon. The method is confirmed by running a series of numerical experiments simulating tidal hydrodynamics in the Papas lagoon. The question of how to alter the tidal amplitude is briefly touched upon, by numerically testing the performance of artificially macro-roughening an inlet and alternatively, designing an inlet to have a meandering shape. It was found that both modifications produce a diminished tidal amplitude, providing positive evidence for the applicability of the proposed method.