Multi-factor tracking of tidal processes in an intermittently open estuarine lake

Abstract

A multi-factor approach to the assessment of the dynamics of the entrance of small, intermittently open and closed estuarine lakes and lagoons, utilising publicly available data, has been developed. Both conventional and novel methodologies have been employed to provide a more robust evaluation and to expand the range of timescales that can be resolved from these databases. This has been applied to an example on the south coast of NSW, Australia (Durras Lake) to illustrate the methodology. A 20 year water level record was available, including 10 closure and breaching events and with ample time for long period patterns to be identified and studied. The study has shown that these intermittent estuaries have a sequence of regime states, with progression from one regime to another, driven by external forcing. Forcing processes are primarily catchment inflow, ocean waves and ocean tide. The study develops and demonstrates a novel sequence of qualitative and quantitative methods to provide an understanding of varying processes in an intermittently open estuarine lake system. From these analyses, a more comprehensive classification and sequence of different entrance regime states is developed. The analyses and the regimen identified may be applied to any similar estuarine system, facilitating the making of more complete and more robust predictions of entrance conditions. Links to the software are given.