Tidal Inlet Dynamics Research Papers (original) (raw)
The Dutch coast consists of beach barriers and tidal inlet systems which dynamically developed during the Holocene. The resulting coastal plain geology has been studied extensively since the beginning of the 20th century, in various ways... more
The Dutch coast consists of beach barriers and tidal inlet systems which dynamically developed during the Holocene. The resulting coastal plain geology has been studied extensively since the beginning of the 20th century, in various ways and from different backgrounds. Today, a large amount of heterogeneous data and many regional studies are available. However, the overwhelming quantities make that knowledge tends to stay fragmented. To analyze coastal system dynamics at millennial time scales, an overview and integration of knowledge on coastal development is required. Therefore, a GIS-system has been developed, expanding on methods for mapping the Rhine-Meuse delta. The new GIS-system documents the accumulated knowledge on individual geological-geomorphological elements and allows to map coastal evolution from past to present. The system links digital base maps (extent of geological-geomorphological elements) and database tables (dating, lines of reasoning, references to sources), which both are dynamically updatable. The system combines this data in scripts to produce palaeogeographical maps for times of choice, as far as data allows. It enables supraregional comparison of coastal plain development, along the entire Dutch coast, and its local and regional forcings by quantitatively analyzing sea ingression dynamics. Both academic and applied research can benefit from this integrated reconstruction.
Turbulence and sediment transport models are incorporated into a three-dimensional hydrodynamics model to investigate the mechanisms of morphologic evolution of scour holes within the Indian River Inlet, Delaware, USA. The inlet bed had... more
Turbulence and sediment transport models are incorporated into a three-dimensional hydrodynamics model to investigate the mechanisms of morphologic evolution of scour holes within the Indian River Inlet, Delaware, USA. The inlet bed had eroded slightly since stabilizing the channel walls in late 1930s through 1976. The mean rate of bed erosion roughly doubled as a response to anthropogenic activities within the inlet such as the removal of~80 piles remaining from an old bridge. Severe erosion near the in-water bridge supports and cofferdams for the replacement bridge necessitated channel bed stabilization that along with the remained debris from the removal of old bridge piles enhanced the growth of two deep scour holes on the bayside and oceanside of the bridge cofferdams. Scour hole and channel bed evolution has decreased drastically since 1994. The present investigation suggests that, initially, flow concentration through the cofferdams of the replacement bridge was the main reason for scour hole development. Bed shear stress over the forward-facing slope of the scour hole entrains sediment from the bed and extends the scour hole along the inlet and in the vertical direction. Flow separation within the developed scour holes after channel bed stabilization enhances turbulence and appears to be the dominant mechanism for further scour hole development.
Recently obtained high-resolution seismic records, collected offshore the western Netherlands in a kilometer-size grid across the lower shoreface and inner shelf, suggest the presence of a dense, previously unknown network of... more
Recently obtained high-resolution seismic records, collected offshore the western Netherlands in a kilometer-size grid across the lower shoreface and inner shelf, suggest the presence of a dense, previously unknown network of tidal-channel fills in the shallow subsurface of the North Sea. Seven channel fills constituting this network were analyzed in detail to infer relationships among the fills in time and space, and to identify factors governing channel development and tidal-basin evolution. The majority of the channels are oriented perpendicular to the coast, but parts of some have a strong coast-parallel component. Shell associations and sedimentological characteristics in most channel fills are typical of back-barrier depositional environments. All but one of the channel fills are part of an Atlantic-age tidal-channel system, draining a tidal basin protected by barrier islands. One channel fill, which is correlated to an incision recognized onshore, represents a younger phase in coastal development. The presumed barrier-island chain was positioned at least 12 km seaward of the present coastline in the northern part of the study area, and at least 6 km seaward of the present coastline in the southern part. The tidal channels grew and migrated actively before partially being filled in between 7300 14C yr BP and 5500 14C yr BP, reflecting an initial tidal-prism increase followed by a substantial decrease. The tidal-prism increase was governed by an upsurge of the tidal amplitude between 8000 14C yr BP and 7000 14C yr BP, and the subsequent decrease by a gradual decrease in the rate of sea-level rise. Rapid retrogradation of the coastline put a sudden end to the existence of the tidal basin. The ensuing shoreface erosion removed all but the deepest parts of the channel fills, which do not show any evidence of systematic landward migration. This field observation corroborates recent modeling results suggesting that rapidly rising sea level may create the conditions necessary for overstepping of sandy barriers.