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Morphological monitoring is fundamental to the understanding of coastal morphodynamics, and should provide a comprehensive awareness of coastal behaviour in response to storms, climate, sea-level change and human activities on different scales, when supported by historical (meso-) scale examinations of coastal change.

Concepts pertaining to our understanding of estuarine dynamics have been heavily influenced by work carried out on the east and west coasts of the United States and western Europe (). Antecedent geological controls have played an important role in predetermining the dominant type of estuaries along these coasts, namely drowned river valleys on coastal plains and fjord type systems tuned to moderate/high tidal regimes. Along the northern Gulf of Mexico (Fig. 1), however, estuaries are predominantly bar-built where the latest Holocene “stillstand” in sea level has permitted waves to build barrier islands/spits/beaches supplied by sediment from updrift and offshore sand sources (; ). Tides in the Gulf of Mexico are microtidal (0–0.3 m), predominantly diurnal and mixed (). Characteristically broad regions of low bathymetric relief result in minimal bathymetric steering of the otherwise low-frequency flow (). Due to a high incidence of tropical cyclones in the northern Gulf (; ), low profile barriers are susceptible to multiple breaches and inlet development. Such occurrences play an important role in estuarine circulation patterns due to phase lags in tidally driven waves. These interlinkages have, however, yet to be fully explored ().

Delta-building in the Holocene Mississippi River system is characterized by the successive construction and abandonment of delta lobes (; ; ). Each major delta-building episode is accompanied by a rather orderly and predictable set of events starting with stream capture followed by filling of an interdistributary basin with lacustrine deltas and swamp deposits, building of a bayhead delta at the coast, and finally construction of a major shelf delta. The process of “delta switching” involves the initiation of a new major delta while the previously active delta is systematically abandoned. These changes associated with shifting fluvial input are commonly referred to as the “delta cycle” (). Each major delta lobe in the Mississippi River system is active for about 1000–1500 years.

Renowned as the site of the world’s most infamous railway accident, the so-called Tay Bridge Disaster of 1879 (), the Tay Estuary of eastern Scotland is one of the most widely studied in the country, especially in terms of geological and geomorphological processes. Over the past four decades in particular, numerous studies of the sedimentology and hydrodynamics of this complex, macrotidal system have been undertaken, largely by researchers from the University of Dundee using the boats and equipment of the dedicated Tay Estuary Research Centre. The database (http://www.dundee.ac.uk/crsem/TEF/review.htm - currently containing over 300 entries) recently compiled by the Tay Estuary Forum (a voluntary partnership established in 2000 “to promote the wise and sustainable use of the Tay Estuary and adjacent coastline”), provides an impressive but still incomplete inventory of the published and unpublished research that has been undertaken on this water body.

Embayed coastlines with fluvial bedload contribution are found in many parts of the world. Due to limited longshore sediment transport, fluvial sediment supply, sea-level history and changes in accommodation space are the primary factors controlling the formation and evolution of a variety of coastal accumulation forms (; ; ; ; ; ). However, few studies have addressed the sedimentological relationships between fluvial systems and associated barrier sequences at millennial time scales, particularly along formerly glaciated coasts (; ; ; ; ; ; ). In areas where the geological record of an initial fluvial vs. inner shelf sediment contribution is ultimately related to a common fluvial source, it may be difficult to establish the link between sediment transport pathways and coastal depocenters. In addition, such records are often confined to the deeper parts of the barrier sequences and require extensive coring efforts. The mouth of the Kennebec River, Maine, USA, and the associated Holocene barrier systems of Popham and Seawall Beaches (Fig. 1) provide an ideal setting for evaluating the use of bulk sedimentological properties of recent fluvial-estuarine and nearshore sediments in barrier-stratigraphic research.

The bedrock framework of the northern Gulf of Maine coast, USA (Fig. 1), controls the geometry of headlands and embayments (, ; ). Quaternary continental glaciers sculpted this paraglacial coast, culminating in the latest Wisconsinan Laurentide Ice Sheet, which reached its maximum extent in the region 20–22 ka (). This ice sheet was marine-based in much of the Gulf of Maine 20–15 ka () and during later stages of retreat through the Maine coastal lowlands (; ). Sediments of a wide variety of () were deposited duringeglacial retreat, interpreted in a sequence-stratigraphic model by Belknap and Shipp (1991) and Barnhardt et al. (1997). Sediment sources to the evolving Holocene coast included reworking from glacial and glaciomarine outcrops, as well as limited fluvial inputs.