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The purpose of this study was to analyse the shoreline movement of the Niger delta, specifically focusing on the spatial pattern of the delta's shoreline behaviour during 1986–2019. We employed satellite data of medium spatial resolution (20–30 m) to delimit the delta shorelines representing specific time in order to determine the rates of the delta shoreline migration. Our results show that the delta shoreline has changed nearly in equal proportion between erosion (50.3%) and accretion (49.7%), at mean (maximum) rates of 3.9 m/yr. (26 m/yr.) of erosion, and 4.0 m/yr. (27 m/yr.) of accretion. Further analysis indicates that the highest shoreline migration is seaward (>200 m) though the ratio of the shoreline distance in recession (54%) exceeds that which is in accretion. Our analysis did not reveal any entrenched spatial pattern of shoreline behaviour but rather highlights a random occurrence of hotspots in both shoreline erosion and accretion over space and time. We have also showed that by applying the statistical mean-removed shoreline approach, the overall trend of a delta shoreline movement can be vividly discriminated. In conclusion, since the Niger delta shoreline dynamics is most intense at the delta river mouths, we suggest this is likely due to the interaction between waves and river discharge in these locations. [ABSTRACT FROM AUTHOR]

Mars' controversial hypothesized ocean shorelines have been found to deviate significantly from an expected equipotential surface. While multiple deformation models have been proposed to explain the wide range of elevations, here we show that the historical locations used in the literature and in these models vary widely. We find that the most commonly used version of the Arabia Level does not follow the originally described contact and can deviate laterally by ∼500 km in Deuteronilus Mensae. A meta‐analysis of different published maps shows that, globally, the minimum lateral offsets between the locations of the putative Arabia and Deuteronilus shorelines vary by an average of 141 ± 142 km and 180 ± 177 km, respectively. This leads to mean elevations of the Arabia Level that vary by up to 2.2 km between different mappings, and topographic ranges within each global mapping ranging from 2.7 to 7.7 km. The younger Deuteronilus Level has less topographic variation as it largely follows a formal contact (the Vastitas Borealis Formation) within the relatively flat northern plains. Given the high variance in position (spatial and topographic) of the maps, the use of such data and conclusions based on them are potentially problematic. Plain Language Summary: Whether oceans ever existed on Mars is controversial, with support largely coming from hypothesized ancient shorelines. As with modern shorelines on Earth, possible ancient martian shorelines are expected to be approximately level, but past studies found that the two main global shoreline mappings have elevation ranges from about one to several kilometers, respectively. Here, we remap segments of the proposed shorelines based on their original geomorphic definitions and find that modern maps vary laterally by hundreds of kilometers from our segments mapped using higher‐resolution data. Additionally, we compare maps of potential shorelines over time. We find that maps are both inconsistent and inaccurate with their placement of hypothesized shorelines. Lateral offsets between different maps locally exceed a thousand kilometers. This disagreement with the poorly understood location of the potential shorelines can explain, in part, the observed elevation differences. Our results question the usefulness of putative shorelines as evidence for ancient martian oceans and implies the need for more detailed, revised mappings and scrutiny. Key Points: Remapping segments of the putative Mars shorelines finds modern interpolated maps diverge up to 500 km from original geomorphic mapsPublished maps of the Arabia and Deuteronilus Levels have similar mean lateral offsets of 140 and 180 km with 1,000 km max offsetsA large portion of the topographic disparity of the Arabia Level may be explained through these inconsistent mappings over time [ABSTRACT FROM AUTHOR]

Although modern wave-dominated shorelines exhibit complex geomorphologies, their ancient counterparts are typically described in terms of shoreface-shelf parasequences with a simple internal architecture. This discrepancy can lead to poor discrimination between, and incorrect identification of, different types of wave-dominated shoreline in the stratigraphic record. Documented in this paper are the variability in facies characteristics, high-resolution stratigraphic architecture and interpreted palaeo-geomorphology within a single parasequence that is interpreted to record the advance of an ancient asymmetrical wave-dominated delta. The Standardville (Ab1) parasequence of the Aberdeen Member, Blackhawk Formation is exposed in the Book Cliffs of central Utah, USA. This parasequence, and four others in the Aberdeen Member, record the eastward progradation of north/south-trending, wave-dominated shorelines. Within the Standardville (Ab1) parasequence, distal wave-dominated shoreface-shelf deposits in the eastern part of the study area are overlain across a downlap surface by southward prograding fluvial-dominated delta-front deposits, which have previously been assigned to a separate ‘stranded lowstand parasequence’ formed by a significant, allogenic change in relative sea-level. High-resolution stratigraphic analysis of these deposits reveals that they are instead more likely to record a single episode of shoreline progradation characterized by alternating periods of normal regressive and forced regressive shoreline trajectory because of minor cyclical fluctuations in relative sea-level. Interpreted normal regressive shoreline trajectories within the wave-dominated shoreface-shelf deposits are marked by aggradational stacking of bedsets bounded by non-depositional discontinuity surfaces. Interpreted forced regressive shoreline trajectories in the same deposits are characterized by shallow incision of fluvial distributary channels and strongly progradational stacking of bedsets bounded by erosional discontinuity surfaces that record enhanced wave-base scour. Fluvial-dominated delta-front deposits most probably record the regression of a lobate delta parallel to the regional shoreline into an embayment that was sheltered from wave influence. Wave-dominated shoreface-shelf and fluvial-dominated delta-front deposits occur within the same parasequence, and their interpretation as the respective updrift and downdrift flanks of a single asymmetrical wave-dominated delta that periodically shifted its position provides the most straightforward explanation of the distribution and relative orientation of these two deposit types. [ABSTRACT FROM AUTHOR]

The coastline of Hai Hau District, located on the northeast coast of Vietnam with about 30 km of shoreline, is chronically eroding. Previous studies have tried to highlight the main causes of the erosion along this coastline, and several hypotheses exist. To examine the hypothesis that gradients in the longshore sediment transport rate and cross-shore fine sediment lost offshore are the main causes generating the serius erosion at Hai Hau Beach, a newly developed numerical model of shoreline change based on the one-line theory was applied and compared with data. Sea dike segments, reinforced by stones and mortar, were modeled using a seawall boundary condition, and the sediment continuity equation was modified to take into account the offshore transport of fine-grained sediment. The simulated shorelines agreed well with the measured shorelines, both for the calibration and validation periods. The calculated sediment budget shows that the net sediment transport is in the southward direction and that a large amount of finegrained sediment is lost into deep water. These two sinks of sediment are believed to be the main causes of the serious erosion at Hai Hau Beach. [ABSTRACT FROM AUTHOR]

The geomorphology and processes of land loss in the Pontchartrain Basin for the period 1990-2001 are mapped and the results of the classification presented. This data set is compared to an earlier classification, which covered the period 1932-1990 to determine the status and trends of wetland loss in the Pontchartrain Basin between 1932 and 2001. Results of the land loss classification indicate land loss rates have remained steady between the two periods (13 km2/y between 1932 and 1990 and 12 km2/y between 1990 and 2001). The geomorphology and processes of loss have shifted from primarily interior loss as a result of direct removal and submergence in the first period to primarily shoreline loss as a result of erosion in the second period. Three areas of concentrated land loss between 1990 and 2001 represent portions of the upper, middle, and lower basin. Land loss at all three locations shifts from interior to shoreline loss between the two periods. In the second period, interior loss through the process of submergence is still occurring but at much reduced rates at locations 1 and 2. Interior loss through the process of direct removal is only occurring at location 1 during the second period and accounts for less that 2% of the loss. At location 3, land loss is completely in the form of shoreline erosion during the second period. [ABSTRACT FROM AUTHOR]

The indentation index, which is the ratio between the real length of a coast and its Euclidean length, is a parameter applied to characterize rock coasts and to study their evolution. Rather than subjectively selecting two or more sectors of a rock coast, the method proposed in this paper considers analyzing the indentation index on the same coastline previously split into several adjacent tracts with equal Euclidean length. By digitizing the coastline in a GIS environment, it becomes possible to test several Euclidean length values on the same coastline, obtaining a different spatial variability of the indentation index with each trial. The best length values that maximize the spatial variability of the indentation index are those that determine an indentation index pattern characterized by high variance and low spatial autocorrelation. The spatial distribution of the indentation index can eventually be analyzed considering known littoral forces acting on the studied coast. When more than one Euclidean length value is found to maximize the variability of indentation index within the same coast, it is likely that there are one or more littoral forces acting or interacting differently at different scales. [ABSTRACT FROM AUTHOR]

A ground-penetrating radar survey of a newly formed series of beach ridges along the southern Azerbaijan coast, Caspian Sea, illustrates rapid coastal response to the most recent sea level fall of 0.8 m in the Caspian Sea between 1995 and 1999. Effects of seasonal sea level fluctuations as well as individual storm occurrences can be linked to depositional beds on the ground-penetrating radar profiles. The beach ridge system is swash built and formed primarily under fair weather conditions. Ridge and swale topography can be related to seasonal sea level change. The rapid sea level change in the Caspian Sea combined with surface and subsurface data on coastal beach ridges provides a unique opportunity to observe and reconstruct coastal evolution at a resolution not possible along other oceanic coasts. [ABSTRACT FROM AUTHOR]

The article presents Brian Sissons and his research with D. E. Smith and R. A. Cullingford on the "Lateglacial and Postglacial Shorelines in South-East Scotland" which was published in 1966 in the journal "Transactions of the Institute of British Geographers." Sissons and others described the Scotland's Lateglacial and Halocene relative sea-level change in the research. Likewise, they were able to provide and to summarize new geomorphological and stratigraphic data on various raised and buried shorelines.

Dredged materials from maintenance and deepening of inlets on coastal barriers are typically transported for disposal in deep water or on land. An alternative is to treat dredged materials as a resource, placing them on the ebb-tidal delta or subtidal shoals at depths where they are retained within the long-shore transport system and can nourish eroding down-drift beaches. Deposition of sediments onto subtidal shoals may, however, bury and selectively kill populations of benthic invertebrates, or indirectly alter assemblages by modifying sediment characteristics. Core sampling of the eastern (control) and western (disturbed) sides of Beaufort Inlet, North Carolina, twice before and once 8 months after a large (660,000 m³) disposal revealed significant coarsening of sediments and associated changes to assemblages of benthic macroinvertebrates in response to the perturbation. Impacts to sediments and macroinvertebrates were closely correlated and, although greatest where sediment was directly deposited, extended over a wider (at least 1 km to the east) area than the deposition. Of the taxa comprising faunal assemblages, spionid polychaetes were most affected by the disposal, declining in abundance. These results, which tie the deposition and dispersal of coarse sediments on an ebb-tidal delta to changes in benthos, imply a biological cost that may be less than that of direct nourishment of biologically productive intertidal beaches. [ABSTRACT FROM AUTHOR]

Field biological and geomorphological observations in certain East Asia coasts permit definition of Mean Sea Level (MSL) with an accuracy of ~10 cm, that is, a vertical geodetic datum, as well as recognition of the MSL of fossil shorelines, up to a few thousand years old, mainly associated with tectonic/seismic effects. Subsidence produced by compaction of nearly-surficial strata seems also to be a usual effect. These data indicate that datum variability is a widespread effect in East Asia, time-dependent even at time scales affecting engineering works, but only in a few cases fully predictable. [ABSTRACT FROM AUTHOR]