On the Hydrodynamic Geometry of Flow-Through versus Restricted Lagoons

Nikolaos Fourniotis,Georgios Leftheriotis,Georgios Horsch

doi:10.3390/w10030237

Nikolaos Fourniotis, Georgios Leftheriotis + Show 1 more

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https://doi.org/10.3390/w10030237

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Abstract

The classification of a lagoon as a restricted lagoon is shown to depend not solely on its geometry but also on the tidal hydraulics. By numerically simulating the tidal exchange of two lagoons of similar geometrical dimensions, the Nidova lagoon and the Papas lagoon, in Western Greece, subject to very similar tidal forcing, applied to the two tidal inlets in the first case and three in the second, very different residence times are found, namely 2.5 days for the Nidova and 25–30 days for the Papas lagoon. This large difference is attributed to the fact that whereas the Papas lagoon functions as a typical restricted lagoon, in which the water renewal is achieved by mixing in the lagoon of the tidal prism water exchanged within a tidal cycle, the Nidova lagoon functions as a flow-through system because of the differential arrival of the tide at its two tidal inlets. It is suggested that this way of enhancing the flushing rate of a lagoon be considered, whenever possible, when creating a new tidal inlet to the lagoon.

Highlights

Coastal lagoons are important for fisheries and extensive or intensive aquaculture in many areas of the world, since marine fish species migrate towards lagoons, which provide favorable conditions for feeding and shelter [1]
Characteristics ofofthe the Nidova the Papas lagoon communicate the Gulf of Patras: the former is BothBoth the Nidova and and the Papas lagoon communicate withwith the Gulf of Patras: the former is situated situated in the northwest, whereas the latter is in the southwest of the
Restricted lagoons suffer from long residence times, which result because of the limited tidal

Summary

Introduction

Coastal lagoons are important for fisheries and extensive or intensive aquaculture in many areas of the world, since marine fish species migrate towards lagoons, which provide favorable conditions for feeding and shelter [1]. In Greek waters, important fishing and extensive aquaculture activities have been developed in the majority of lagoons (30 in the Aegean and 46 on the Ionian coast), occupying a total area of about. The fishery exploitation is based on traditional barrier fish traps These are permanent entrapment devices and the catches are based on the species-specific inshore–offshore seasonal or ontogenic fish migration [3]. The majority of these extensive lagoon systems are located in western and northern Greece. The Messolonghi lagoon system covers about 15,000 ha [4] (p. 97), while the

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