Coastal Sediment Cell Research Articles

A new approach to mapping littoral cells within a tide-dominated embayment

Western Port is a large tide-dominated embayment located 75 km east of Melbourne, Victoria that is flanked by a rapidly growing population, significant industrial infrastructure, grazing lands and protected RAMSAR habitats. Remarkably little is known about the sediment dynamics of Western Port despite concerning rates of erosion of the swamp and floodplain deposits including cohesive clay cliffs that fringe the sunkland. As in other tide-dominated systems, sediment dynamics in Western Port are complicated by strong tidal currents, multiple sediment sources and complex circulation. We applied the coastal sediment cell framework to Western Port, in conjunction with high resolution satellite derived rates of coastal change to elucidate sediment sharing among the sub-embayment beaches. Using end member modelling of 20 sediment assemblages based on elemental and mineralogical composition we robustly identified seven end members that correspond to different point and diffuse provenances. Hierarchical clustering of the 20 beaches dispersed across the bay yielded nine coastal cells, delimited by headlands, deep water channels, estuaries or disruptive infrastructure. Analysis of shoreline change within the cells suggests most cells are neutrally or positively balanced but a northward movement of sediments is leading to rotation. The deep channels provide a pathway for Bass Strait sediments to bypass the embayment headlands and tidal currents enable cross shore exchange with the channels beyond wave derived closure depth in some locations. Understanding the sediment cell boundaries and direction of sediment transport can assist with the management of erosion hotspots; the novel approach applied here can resolve complex connected coastal systems such as estuaries and embayments.

Study of dynamics of coastal sediment cell boundary in Cirebon coastal area based on integrated shoreline Montecarlo model and remote sensing data

The dynamics of the coastal cell boundary in the Cirebon coast have been investigated. The edge of the sediment cell is unique, with a river mouth and very active shoreline movement. A groin-like structure model with the sediment output at the end of the structure is solved analytically using Laplace transforms methods. The morphological changes of these cell sediment boundaries were analyzed using modeling, field measurements, and Landsat satellite data. The study area consists of a single cell with boundaries of fine sediments containing coral fractions. The middle cell is generally a beach with mangroves with fish or a salt pond beach. The observations using Landsat imagery from 1978 to 2021 show changes in the boundary of sediment cells moving forward to the west as far as 1230 m. We use 1985 as the initial cell boundary for our modeling, with a cell boundary length of 1200 m from the shoreline. The first scenario with constant sediment rate input get shoreline changes from 1100 m from the cell boundary. Still, a linear sediment rate results in the coastline moving upward to 1190 m. The third scenario with periodic sediment input with a monsoon period gives a coastline addition of 750 m at the estuary of the cell boundary and erosion (240 m) in an area far from the cell boundary. The Montecarlo simulation generates a breaking wave with a Gaussian random function that produces a breaking wave height with a dominant variation between 0.5 - 1.5 m. The evolution of the coastline with a constant sediment rate resulted in the most developed beach as far as 1000 m with a relatively large chance of reaching 4000. As for the linear rate, producing a coastline with the highest probability of about 1200 m and periodic sediment rates created the most significant for the coastline between 1000–2500 m.

Sediment cells and their dynamics along the coasts of India – A review

Coastal zone is dynamic in nature and is subjected to multiple interactions from marine, terrestrial, atmosphere, biosphere, fluvial systems and tectonic processes besides human interventions. Each coast is unique to its geographical location and set of physical interactions between land and oceanic parameters. Understanding these interactions are challenging and complicated in perception of its sustainability. A central concept in developing such a holistic approach is to view the coast as discrete functional units termed as ‘Sediment Cells’ rather than viewing it as a single continuous stretch of land surface. Sediment cell approach will provide a better understanding of the interrelation between the functions of the short term coastal processes and long term response and recovery of the coast. Based on sediment cell approach, a study was undertaken to delineate discrete functional units along the west and east coasts of varying spatial scales with confined sediment movement. Long term morphological changes, short term coastal processes and sediment dynamics were considered for the delineation. A total of 26 primary cells with 10 on the west and 16 on the east were identified from the study. These primary cells were further sub divided into 58 sub cells with 21 on the west and 37 on the east based on the sediment interruption factors either natural or manmade. The identified coastal sediment cells can be used in Integrated Coastal Zone Management (ICZM) especially to deal with shoreline changes and in the preparation of Shoreline Management Plans (SMP). To be specific, the delineated coastal sediment cells from the study are being used for the preparation of ICZM plans for Odisha and West Bengal.

Influence of Amenities in the Functioning of a Coastal Sediment Cell with a Moving Barrier: Case of Benin Coastal Segment between Hillacondji and Djondji in the Township of Grand Popo

Influence of Amenities in the Functioning of a Coastal Sediment Cell with a Moving Barrier: Case of Benin Coastal Segment between Hillacondji and Djondji in the Township of Grand Popo

Coastline evolution of Portuguese low-lying sandy coast in the last 50 years: an integrated approach

Abstract. Regional/national-scale information on coastline rates of change and trends is extremely valuable, but these studies are scarce. A widely accepted standardized methodology for analysing long-term coastline change has been difficult to achieve, but it is essential to conduct an integrated and holistic approach to coastline evolution and hence support coastal management actions. Additionally, databases providing knowledge on coastline evolution are of key importance to support both coastal management experts and users.The main objective of this work is to present the first systematic, national-scale and consistent long-term coastline evolution data of Portuguese mainland low-lying sandy coasts.The methodology used quantifies coastline evolution using a unique and robust coastline indicator (the foredune toe), which is independent of short-term changes.The dataset presented comprises (1) two polyline sets, mapping the 1958 and 2010 sandy beach–dune system coastline, both optimized for working at 1 : 50 000 scale or smaller; (2) one polyline set representing long-term change rates between 1958 and 2010, each estimated at 250 m; and (3) a table with minimum, maximum and mean of evolution rates for sandy beach–dune system coastline. All science data produced here are openly accessible at https://doi.pangaea.de/10.1594/PANGAEA.859136 and can be used in other studies.Results show beach erosion as the dominant trend, with a mean change rate of −0.24 ± 0.01 m year−1 for all mainland Portuguese beach–dune systems. Although erosion is dominant, this evolution is variable in signal and magnitude in different coastal sediment cells and also within each cell. The most relevant beach erosion issues were found in the coastal stretches of Espinho–Torreira and Costa Nova–Praia de Mira, Cova da Gala–Leirosa, and Cova do Vapor–Costa da Caparica. The coastal segments Minho River–Nazaré and Costa da Caparica adjacent to the coast exhibit a history of major human interventions interfering with the coastal system, many of which originated and maintained a sediment deficit. In contrast, the coastal segments Troia–Sines and Sines–Cape S. Vicente have experienced less intervention and show stable or moderate accretion behaviour.

History and influence of the Danube delta lobes on the evolution of the ancient harbour of Orgame (Dobrogea, Romania)

On the coast of Northern Dobrogea, south of the Danube delta, the Greek settlement of Orgame was founded in the mid 7th c. BC, probably by Milesian colonists. The ancient city was located on the Cape Dolojman which today overlooks a large lagoon complex. We undertook a chronostratigraphic study to: (i) understand coastal changes around Cape Dolojman since ca. 5000 years BP in connection with the construction of the Danube delta lobes, and (ii) identify potential sediment impacts related to human occupation of the site. Three cores were extracted from the lagoon area. Sedimentological and biological analyses were undertaken to reconstruct the evolution of the coastal palaeoenvironments. The results show a closure of the marine bay around 3500 cal. BP and its transformation into a lagoon environment. The first major environmental change was due to the construction of the lobe St. George I and the formation of the barrier Lupilor. Around 2000 cal. BP, the formation of an intra-lagoonal lobe, the Dunavatz, led to the gradual transformation of the lagoon into a fluvial-dominated system. Paradoxically, lagoon waters today still wash the ancient Greek harbour environment, which has not been totally infilled by alluvial sediments. To understand this paradox, in a context of coastal progradation, we compared and contrasted the geomorphological data with the nearby city of Istros/Histria, which was already landlocked at this time. The location of these two Greek colonies relative to the coastal sediment cell and barriers partly explains their contrasting palaeoenvironmental evolution. Until 2650 cal. BP, the increase in charcoal and organic matter in sedimentary archives is interpreted as an anthropogenic signal for a more extensive use of the vegetation cover following the foundation of the city of Orgame (e.g. for domestic use and funeral rites).

Coastal sensitivity assessment for Thiruvananthapuram, west coast of India

The densely populated coastline of Thiruvananthapuram district of Kerala, along the southwest coast of India, is sensitive to sea surge and severe coastal erosion. The December 2004 Indian Ocean Tsunami had inundated several parts of this coastal zone, indicating nature of sensitivity. The present study is an attempt to develop a coastal sensitivity index (CSI) for Thiruvananthapuram coast within the framework of coastal sediment cells. Seven variables, namely (a) coastal slope, (b) geomorphology, (c) shoreline change, (d) mean sea-level rise, (e) nearshore slope, (f) significant wave height and (g) mean tide range, were adopted in calculation of CSI (the square root of the product of the ranked variables divided by the number of variables). Remote sensing data, topographic maps supported by field work and data from numerical models are used in geographic information system environment to generate CS index for each kilometer segment of this 76-km coastline. This study reveals that 72 % of the Thiruvananthapuram coastline falls in the high sensitive category. This exercise, first of its kind for Kerala coast will be useful for disaster mitigation and management.

A 150-year record of coastline dynamics within a sediment cell: Eastern England

Coastal sediment cells reflect processes operating at a range of scales, but it is the medium spatial and temporal scales (decades to centuries) that are of greatest interest for coastal management. This paper focuses on coastline position change within a single sediment cell over 150years where the geomorphology includes cliffs, beaches and saltmarshes. The focus is the east coast of England from Flamborough Head to Gibraltar Point. Although the updrift sector of this sediment cell has been studied for well over a century, the downdrift sector has attracted significantly less attention. Using topographic profiles, bathymetric profiles, aerial photographs and historical maps we mapped coastline erosion and accretion using the Digital Shoreline Analysis System (DSAS) and calculated volumetric changes for different morphometric units. Rapid erosion of the updrift Holderness cliffs has been counterbalanced with accretion on beaches along the downdrift Lincolnshire coast. The amount of accretion in Lincolnshire corresponds to around 29% of the volume of sediment eroded from Holderness. Much of the eroded cliff material is likely to be deposited temporarily into nearshore and offshore sand banks before being redistributed by cross-shore currents. An exploration of storm surge impact on long-term erosion and accretion rates showed no clear relationship between storm surge frequency and change in coastline position, however this may be in part due to the relative timing of storm occurrence and data acquisition. The Jenkinson daily weather type classification was found to be a reasonable proxy for the occurrence of strong onshore winds which may offer scope for further investigation of the role of forcing factors over time periods beyond the length of the meteorological and tidal station records. Winter North Atlantic Oscillation phase was not a good indicator of storminess on the east coast of England but may be a useful proxy for quiescence.

The management of Pevensey shingle barrier

The shingle (gravel) barrier beach at Pevensey Bay (East Sussex, UK) protects rare habitat, properties, trunk roads and other assets from flooding and erosion. The beach is managed in an adaptive manner by a private consortium, based on a 25 year contract. The practices developed at Pevensey are shown to fit into the frame of reference approach, adapted for the English policy and management framework. The barrier beach is managed to retain a favourable sediment status, although the concept has no official recognition, thereby ensuring that the barrier is sufficiently resilient to maintain its functions between interventions. The concept of favourable sediment status is considered a potentially useful way of summarising the status of the beach at Pevensey as it combines management objectives and processes (through coastal state indicators) with the availability of supply. The concept of the coastal sediment cell is important, but not sufficient, for identifying policy units at Pevensey as smaller-scale processes are also important. Two offshore dredging areas constitute the strategic sediment reservoir for Pevensey, although the term ‘strategic sediment reservoir’ has no official recognition and there is no long-term guarantee of supply.

Implementation of coastal erosion management in the Netherlands

The Netherlands is a low-lying country, in which 9 million people are living below sea level and 70% of the gross domestic product is being earned in areas below sea level. Therefore, protection against flooding is traditionally the primary focus of coastal policy in the Netherlands. Analysis shows that characteristics of Dutch coastal management very well comply with the recommendations and key concepts to support sustainable coastal management as issued by the EU in 2004 (EUROSION). Sediment management represents the core of erosion management in the Netherlands; key concepts like resilience, coastal sediment cells, favorable sediment status and strategic sediment reservoirs, are important building stones. Development and implementation of coastal erosion management in the Netherlands, has implicitly been guided by a systematic Frame-of-Reference. Characteristics of this approach are the definition of clear objectives at different levels (i.e. strategic, tactical and operational) and an operational decision recipe related to policy development and implementation. Application of the Frame-of-Reference to current problems and challenges in Dutch coastal management indicates its ability to reveal shortcomings of the existing approach, and to explore potential solutions. Where EUROSION offers important concepts to define coastal erosion management, the Frame-of-Reference offers a tool to discern different objectives and responsibilities. The combination of both strongly supports implementation of coastal erosion management.

Concepts and science for coastal erosion management – An introduction to the Conscience framework

The main objective of the Conscience project was to develop and test concepts, guidelines and tools for the sustainable management of erosion along the European coastline, based on the best available scientific knowledge and on existing practical experience. Four concepts are potentially capable of providing the nexus between scientific knowledge and management: coastal resilience, coastal sediment cell, favourable sediment status and strategic sediment reservoir. The project has tested the use of these concepts and found that they are useful, provided that they are positioned and linked within a logical structure that we shall call the Conscience “Frame of Reference”, defined in time and space and supported through data and monitoring. Practical experience in six coastal sites in Europe has shown that the use of this Frame of Reference together with these concepts can make management objectives explicit and transparent. It can therefore support the design of an appropriate, resilience based coastal erosion management practice.

Dealing with erosion along the Danube Delta coast. The CONSCIENCE experience towards a sustainable coastline management

The most severe shoreline retreat (over 20 m/year) along the Danube Delta coast has been recorded in the coastal stretch confined by the Sulina branch (north) and Sahalin spit island (south). This erosive trend is caused by the natural evolution of some stretches of the Danube Delta coast, but strongly enhanced by the human activities. Human interventions result in the dramatic decrease in quantity of sediments reaching the coast and in the disruption of natural sediment circulation in the coastal area. EUROSION FP5 Project developed four concepts to be used in coastal studies: coastal sediment cell, coastal resilience, favourable sediment status and strategic sediment reservoir. The main objectives of this study regard the application of the CONSCIENCE methodology and test of the concepts in order to identify and understand the main threats for Sulina – Sahalin littoral cell, especially the coastal erosion one, as well as to provide a sound working methodology for coastal managers to deal with these threats. The sediment budget computed in previous studies, as well as the field observations, indicate a lack of sediments for the littoral cell (unfavourable sediment status). In order to asses the vulnerability of the coast to short term extreme events (especially storms), simulations of water level changes were performed and calibrated with the field observations. A processes based numerical model was used to simulate the storm induced water level variations and the main input data were the bathymetry of the active beach, wind direction and speed (storm scenarios) and the characteristics of water and air. The results show large water level increases for the central part of the study zone, especially for northern wind directions. The main solution proposed to deal the problems arising from a sediment-starved coast, vulnerable to the extreme events, is artificial nourishment. Two strategic sediment reservoirs were identified, both of them at the northern boundary of the cell: the sediments dredged periodically from Sulina mouth and the sediments accumulated in Musura Bay, just north of Sulina jetties. The transfer of these sediments towards the central part of the littoral cell Sulina – Sahalin would decrease the erosion rates to a natural level and restore the natural coastal resilience. The methodology developed in CONSCIENCE Framework and applied to Danube Delta coastal zone provided good results when problems and solutions for the coastal zone were to be identified and tested. This methodology and its related results can be applied by the local coastal managers to Sulina – Sahalin littoral cell, while this experience can be extended to other similar environments facing the same problems.

Managing coastal evolution in a more sustainable manner. The Conscience approach

This paper summarises the main findings of the Conscience research project, whose primary objective was to define and validate, through pilot applications, a methodology to support the implementation, for European coasts, of concepts such as coastal resilience, favorable sediment status, strategic sediment reservoirs and coastal sediment cells. The Conscience conceptual framework to managing coastal erosion has proved to be an efficient tool, because it provides a consistent approach where objective (data) and subjective (desired status) information are analyzed and compared from the standpoint of a consensus target (objective). Moreover, this is done using the best available knowledge and observations, considering always their level of uncertainty, to conduct a sustainable management policy for coastal erosion. The methodology has been tested in field cases from The Netherlands, Poland, Romania, Spain, United Kingdom and Ireland, to cover different time and space scales, together with a wide range of processes and different management objectives.

Function analysis as a coastal management tool: the South Wales coastline, UK

Fifteen beaches from the Swansea Bay coastal sediment cell, South Wales, UK, were analysed via function analysis, involving assessment of specific environmental and socio-economic indicators. These were allocated scores from field surveys and extensive desktop studies, which included beach awards, relevant shoreline management plans, planning and conservation designations and current legislation. Normalised scores allowed production of a conservation/development matrix, enabling beach location in conservation, development or conflict fields, which results appropriately identified. Conservation field beaches tended to have a low density residential hinterland with little or no commercialisation. Conversely, beaches that leant towards the development field had a high density residential hinterland and were highly commercialised. Evaluation showed the importance of planning legislation in conflict areas and identified locations of development potential, where significant environmental consequences would be unlikely. This representation could be used for evolution of conservation/development status within coastal areas, enabling policy adjustment as necessary. It will also enable future sustainability assessment and it is suggested that indicators could be modified to reduce environmental emphasis and provide a more uniform socio-economic consideration.

Viewpoint: The future of coastal policy: making the coast visible to planners

If you go to the coast, you cannot fail to see it or experience it. It is undeniably different from inland areas or offshore areas. However, in the management of coastal activity the coast is much less visible from a policy perspective. In this Viewpoint, I want to take a positive look at the future of coastal policy, in an English context, taking this observation about policy Visibility' as a starting point. The coast comprises the dual mediums of land and water, where the land is surrounded by water rather than the reverse. This seemingly small point is a huge one in its implications. The water medium of the coast represents a huge, dynamic influence which fundamentally affects the climate, ecology and physical nature of the coast, in a wholly different way to the influence that inland waters exert on the surrounding land. In defining the coast one must think initially of where the land meets the sea. We often talk of the shoreline, but because of the rise and fall of the tides this is in fact a zone. It might be very narrow (measured in centimetres: e.g. steep rocky shore in sheltered sea loch) or very wide (measured in kilometres: e.g low-lying sedimentary shore such as the Wash estuary). Furthermore, the conjunction of land and sea gives rise to impacts that extend both inland and offshore, recreational activity being one example, coastal flooding another. Conversely, activities on land or at sea can impact upon the shoreline. Particular farming practices in river basins, for example, can affect coastal water quality. The dredging of marine aggregates can affect the sediment balance in coastal sediment cells, so leading to shoreline change. Thus it is not practicable to define an absolute 'coastal zone' either only the interface between land and sea ought to be included or else everything has to be included. The former is too narrow a definition (and it moves constantly!) and the latter is too wide. This examination of definitions of the coast illustrates the key point that the coast cannot be defined by putting a line around it on a map which will encompass all issues. Any line that is selected is entirely subjective and inherently deficient. Why then is a line on a map so important? The answer lies in the nature of policy as either area-based or issue-based.

Shoreline Management Plans and Coastal Cells in Scotland

Coastal sediment cells have been identified for the Scottish coast and, following the example of England and Wales, a trend is emerging towards the production of shoreline management plans (SMPs) for parts the Scottish coast. However, much of the Scottish coast does not have the degree of intracoastal sediment exchange that gives coastal sediment cells their integrity, and so a cell-based strategy for coastal management may not be a suitable response. This article examines the nature of the sediment cells in Scotland, questions whether the adoption of SMPs for all sections of the coastline is an appropriate management response, and suggests alternatives that may better link to integrated coastal zone management.