Abstract
Abstract This article highlights the impact of tidal inlet modification on the evolution of inland estuarine waterways at the short–medium timescale. The study area is the Nerang River estuarine system located on the east coast of Australia. This estuary has been affected by a range of developments, including stabilization of its tidal entrance. This study is mainly focused on quantifying the tidal regime change and potential morphological and ecological implications resulting from these changes. To this end, the study started with field data collection and numerical modelling of the study area. The results of harmonic analysis showed that the Nerang Estuary responds nonlinearly to tidal forcing and is dominated by frictional forces. Analysis of water level and current time histories showed a mixed, predominantly semidiurnal, and flood-dominant tidal regime within the estuary. It also showed strong asymmetry of tide along the estuary. At the second stage of the study, historical data of the study area wer...
Highlights
Tidal entrances play an important role in the overall dynamics of an estuary
This study involved four sections: (1) Collection of water level, flow velocity, salinity, and temperature data to provide a data set for model calibration; (2) Development of a calibrated tidal model of the study area to provide an insight into the hydrodynamic behaviour of the Nerang Estuary and to identify important nonlinear mechanisms within the estuary; (3) Examination of historical tidal variation at the study area to identify any changes in tidal regime during the past 20 years resulting from the construction of the Gold Coast Seaway; and
This ratio reduces almost 33% between 1984 and 1986. It remains relatively unchanged until 1991, but measurement in the year 2005 shows a further 120% decrease since 1991. These results clearly show that tidal asymmetry and nonlinear responses of the Nerang River Estuary have been reduced during the past 20 years
Summary
Tidal entrances play an important role in the overall dynamics of an estuary. Change in resistance against flow at the entrance has an impact on tidal amplitude and phase (Hinwood and Mclean, 2000) and, on sediment flux into and out of the estuary, flow velocity, and the erosion–deposition regime in the estuary. Tidal entrance behaviour influences the nonlinear interaction between tidal constituents, resulting in changes in asymmetric characteristics of the tide and, influences the morphology, water quality, and ecology of the estuary. The Nerang River tidal entrance has undergone substantial change over the past 20 years. The construction of the Seaway was followed by the dredging of a navigation channel between the Seaway and Sundale Bridge approximately 5 km south of the Seaway at the mouth of the Nerang River.
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