Morphology of coastal lagoon entrances: waves versus tides

Abstract

Tidal inlets are important parts of coastal ecosystems and have been the topic of active coastal engineering research for close to a century. The earliest researchers probably realised that the equilibrium cross-section shape, around which a given inlet oscillates due to changing tides and waves and due to occasional storm surges and/or freshwater floods, can be described in terms of the potential bay or lagoon area and the typical wave and tide parameters for the location. However, till now, the effects of waves and tides have not been combined into an effective parameter for inlet classification or formulae for inlet cross-section area, delta volumes, or morphological time scales. This paper gives such a parameter, which necessarily accounts for tidal period as well as tidal prism and wave height. The effectiveness of this new parameter for quantitative classification of inlets is subsequently demonstrated.