Amin Rahdarian , Karin R. Bryan , Mick Van Der Wegen
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引用次数: 0
Abstract
Estuarine channels convey tidal flow and sediments, while the direction and magnitude of tide-residual transports largely depends on the surrounding estuarine bathymetry, shoals and vegetation cover. This study explores the controls of historic morphodynamics, mangrove development and channels on landscape-scale tidal hydrodynamics around a mangrove-covered estuarine shoal in Whitianga estuary, Aotearoa New Zealand. A Delft3D hydrodynamic model was used to explore the impact of historic developments on spatial flow patterns and flow asymmetry based on an analysis of historical images of the site including conditions of the mangrove forest in the 1940s.
Model results clearly reveal areas of ebb and flood dominance in the model domain, where mangrove surrounded creeks are ebb dominant and shoal incising channels are flood dominant. Within the forest, the seaward part of mangroves is ebb-dominant, whereas a flood-dominance function in the back of the forest with higher elevated mangroves is mostly observed. Removing vegetation leads to a large-scale change in flow routing and flow asymmetry, whereas if creeks are infilled, local changes only around the location of the creeks are observed.
The movement of fine sediment fractions is inferred by the slack water duration at high tide. The existence of vegetation affects the cohesive fraction. Without vegetation, the slack water duration becomes shorter on the shoal close to the fringe, inside and the edge of the former forest while it becomes longer inside the river channel and on the edge of the shoal close to the river channel. In the scenario that channels were infilled, a longer (shorter) slack water duration at the mouth and head of channels and inside channels (around the channels) were observed.
Expansion of mangroves can cause a function shift of the channels. Model results suggest that the ebb-dominant modern-day mangrove creek was flood-dominant in 1940s prior to colonization of mangroves in the inner bend of the shoal.
期刊介绍:
Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.