There is a relative lack of research, targeted models and tools to manage beaches in estuaries and bays (BEBs). Many estuaries and bays have been highly modified and urbanised, for example port developments and coastal revetments. This paper outlines the complications and opportunities for conserving and managing BEBs in modified estuaries. To do this, we focus on eight diverse case studies from North and South America, Asia, Europe, Africa and Australia combined with the broader global literature. Our key findings are as follows: (1) BEBs are diverse and exist under a great variety of tide and wave conditions that differentiate them from open-coast beaches; (2) BEBs often lack statutory protection and many have already been sacrificed to development; (3) BEBs lack specific management tools and are often managed using tools developed for open-coast beaches; and (4) BEBs have the potential to become important in “nature-based” management solutions. We set the future research agenda for BEBs, which should include broadening research to include greater diversity of BEBs than in the past, standardising monitoring techniques, including the development of global databases using citizen science and developing specific management tools for BEBs. We must recognise BEBs as unique coastal features and develop the required fundamental knowledge and tools to effectively manage them, so they can continue providing their unique ecosystem services.

The structure and origin of the Pleistocene (Marine Isotope Stage [MIS] 5) coastal Barrier III in southern Brazil were investigated through analysis of lithofacies, numerical ages, and ground-penetrating radar (GPR) data obtained in outcrops and subsurface deposits. The stratigraphic succession is characteristic of transgressive barriers, with muddy lagoon bottom facies unconformably overlying an older unit (Barrier II) and overlain by landward-dipping lagoon margin and aeolian facies. The back-barrier lagoon was filled with sediments and shells transferred from the foreshore through overwash and/or inlets during the MIS 5e transgressive-high-stand phase, with a higher sea level that reached about +6 to +7 m relative to the present. Marine sediments and shells on the seaward side of the barrier dated to ~100–106 ka indicate another high stand at +4 to +5.1 m during MIS 5c. One shell dated to ~87 ka and aeolian deposits dated to ~82 and ~85 ka suggest a third high stand during MIS 5a that reached at least −2 m relative to the present. The two (possibly three) juxtaposed marine deposits show that Barrier III is a more complex unit than previously recognized, built by successive orbitally forced eustatic sea-level oscillations also recorded in other deposits along the Brazilian coast and worldwide.

Coastal plain stratigraphy is often over looked in paleo–sea-level reconstructions because carbonate sediments do not precisely constrain former sea level. Pacific Island sedimentology provides an invaluable record of geomorphic and environmental consequences of coastal evolution in response to changes in sea level and local tectonics. A series of coastal auger cores obtained from eastern ʻUpolu reveal a subsurface carbonate sand envelope predominately composed of coral and coralline algae derived from the reef framework. Coupling the sedimentological record with geophysical models of Holocene sea level, we identify a critical value (0.3–1.0 m) during the falling phase of the sea-level high stand (1899–2103 cal yr BP) that represents the transition from a transgressive to a regressive environment and initiates coastal progradation. Correlating the critical value with time, we observe nearly a millennium of coastal plain development is required before a small human population is established. Our findings support previous studies arguing that Sāmoa was colonized by small and isolated groups, as post–mid-Holocene drawdown in regional sea level produced coastal settings that were morphologically attractive for human settlement. As future sea level approaches mid-Holocene high stand values, lessons learned from Pacific Island sedimentological records may be useful in guiding future decisions related to coastal processes and habitat suitability.

We present a revised relative mean sea-level (MSL) curve for the Rhine-Meuse delta, western Netherlands, for the period 7900-5300 cal yr BP. The revision is based on a series of new and previously unpublished local groundwater-level index data from buried Late Glacial aeolian dunes in the lower Rhine-Meuse delta, and reinterpretation of existing data.

The new index data consist of (AMS and conventional) radiocarbon dates of samples, collected from the base of peat formed on dune slopes, near Vlaardingen (21 index points), Hillegersberg (one index point), and Hardinxveld-Giessendam (10 index points). The Vlaardingen data represent the coast-nearest Rhine-Meuse delta local water-level record, which therefore is highly indicative for sea-level change. Pollen and macrofossil analysis, and dating of paired samples was carried out to assess the reliability of the groundwater-level index data.

The revision of the MSL curve involves: (1) a significant (0 to >1 m) upward adjustment for the period 7900-7300 cal yr BP; (2) a downward adjustment of <0.25 m for the period 6650-5300 cal yr BP. The new data indirectly support the reliability of the part of the curve for the period 7300-6650 cal yr BP. A longitudinally fairly uniform river gradient of 2.5-3.0 cm/km in the lower Rhine-Meuse delta during the period 6650-5600 cal yr BP can be inferred from the data sets. A significant river gradient extended further towards the coastline than previously thought and it may be that also the revised MSL curve reflects river-gradient effects. An increased floodbasin effect (stronger intra-coastal tidal damping) seems to have developed in the lower Rhine-Meuse delta in de period 7500-6600 cal yr BP, and was probably a complex response to a major avulsion of the Rhine.