Shoreline Management Research Articles

Shoreline management plan for a protected but eroding coast along the southwest coast of India

Coastal erosion is a serious problem of concern along the southwest (SW) coast of India. Various coastal protection measures have been applied for the recovery of the coast, but the devastating effect of erosion still continues. The present study focuses on a coastal stretch situated on the southern sector of the SW coast of India, where Sundar and Sannasiraj (2006) proposed a groyne field along with an existing seawall to control severe erosion. In order to confirm the net littoral drift of this region and for a preliminary assessment of the performance of the groynes prior to construction of the proposed groyne field, two groynes were initially constructed as a pilot program in 2008-09. Periodic monitoring of shoreline position with the two groynes in place was carried out during 2009-14. A shoreline evolution model for the study region was setup, calibrated, and validated using field observations during 2010-11. In addition to traditional shoreline evolution modelling procedures, a profile simulation model was applied for simulating the shoreline behaviour during extreme monsoon seasons. The validated LITPACK model has been used to evaluate the performance of the proposed groyne field in controlling erosion, and the study also considered testing a modified transitional groyne field proposed as an alternative solution to the existing problem, and the modified transitional groyne field was found to be more effective than the prior design. A beach is expected to develop about 30–50m within the groyne cells during the fair season which enhances the possibility of retaining a minimum beach width of 10m during monsoon periods.

Sea-Level Rise and Coastal Submergence along the South–East Coast of Nigeria

Coastal submergence and shoreline retreat constitute a serious threat to shoreline management in the Niger Delta. Short-term and long-term changes on the shoreline adjoining Qua-Iboe River estuary, south-east coast of Nigeria are analysed to assess the impact of sea-level rise and climate change on the shoreline. A comparison of the 2002 and 2013 editions of the maps of the shoreline indicates a landward retreat of the shoreline and a submergence of village of Itak Abasi in the Atlantic Ocean over an estimated area of 180000 m2 along the coastline. Analysis of shoreline changes over neap-spring tidal phase confirmed that the submerged area of the updrift shoreline was threatened by severe and chronic erosion in which the rate has reduced to 178 m3 per day. The downdrift experienced high rate of accretion at 1490 m3 per day with sediment gained from the updrift shoreline and the ebb tidal delta as well as input from fluvial discharge into the estuary. Near-shore wave climate was characterized by the wave breaker heights which fluctuated between 30 cm and 70 cm at a period which ranged between 5 to 8 seconds, the occurrence of edge waves during mid-flood tidal stage along the mid foreshore, predominantly eastward directed long-shore currents and storm surge events at the updrift shoreline are considered as the hydrodynamic processes which caused the shoreline retreat and submergence. The intensity and magnitude of the impact of the processes on the shoreline are attributed to sea-level rise and climate change. Sustainable shoreline management strategies including measures for mitigations and adaptations to climate change are recommended.

Coastal Vulnerability Indices: Constraints and Opportunities of Nagapattinam Region, Tamil Nadu, India

Coastal vulnerability and sensitivity indices accept that the addition of socio-economic variables defining the vulnerable areas. These studies envisage the incorporation of socio-economic variables into a GIS based coastal vulnerability index for shoreline management of Nagapattinam. a socio-economic sub-index was developed to contribute potentially one third of the overall index score, the other components consisted of coastal forcing and coastal characteristic sub-indices. All variables were ranked on separately 1-5 scale with 5 being the most vulnerable. The variables were integrated with sub-indices and the sub-indices were combined to produce theoverall index. Most previously developed coastal vulnerability/sensitivity indices acknowledge that the addition of socio-economic variables would assist in defining vulnerable areas. The area of Nagapattinam having the greatest influence from the socio-economic index as might be expected, given its sheltered position and high level ofinfrastructure of the eleven areas, Velankanni has the highest score in the coastal forcing sub-index, followed by Vettaikaraniruppu, while Velanganni is dominated by the coastal characteristics subindex as is the Nagapattinam.

Marine Shoreline Management—A 35-Year Evaluation of Outcomes in San Juan County, Washington, US

ABSTRACTIn 1976, Washington became the first state to implement the federal Coastal Zone Management Act (CZMA) primarily through the 1971 WA Shoreline Management Act (SMA). However, there has been little effort in Washington to evaluate outcomes of shoreline protection programs post SMA. In 2006–2008, we characterized shoreline conditions in San Juan County over three time periods spanning pre and post SMA and engaged community members to improve effectiveness of shoreline protection. We found modest improvements in forest retention on marine shorelines between pre and post 1977, but few other improvements through time. While we could not measure shoreline construction rates, construction practices for shore armor and overwater structures (docks) have changed very little, despite the increased regulatory standards. The vast majority of shore armor constructed post SMA occurred without mandatory county or state permits likely due to: widespread perception that permits were unnecessary and that permit standards were arbitrary and inconsistently applied; poor understanding of shoreline ecology by community members; lack of county or state enforcement authority and shoreline monitoring programs; and poor permit tracking systems.

Temporal and Spatial Dynamics of Estuarine Shoreline Change in the Albemarle-Pamlico Estuarine System, North Carolina, USA

Many shoreline studies rely on historical change rates determined from aerial imagery decades to over 50 years apart to predict shoreline position and determine setback distances for coastal structures. These studies may not illustrate the coastal impacts of short-duration but potentially high-impact storm events. In this study, shoreline change rates (SCRs) are quantified at five different sites ranging from marsh to sediment bank shorelines around the Albemarle-Pamlico estuarine system (APES) for a series of historical (decadal to 50-year) and short-term (bimonthly) time periods as well as for individual storm events. Long-term (historical) SCRs of approximately −0.5 ± 0.07 m year−1 are observed, consistent with previous work along estuarine shorelines in North Carolina. Short-term SCRs are highly variable, both spatially and temporally, and ranged from 15.8 ± 7.5 to −19.3 ± 11.5 m year−1 at one of the study sites. The influence of wave climate on the spatial and temporal variability of short-term erosion rates is investigated using meteorological observations and coupled hydrodynamic (Delft3D) and wave (SWAN) models. The models are applied to simulate hourly variability in the surface waves and water levels. The results indicate that in the fetch-limited APES, wind direction strongly influences the wave climate at the study sites. The wave height also has an influence on short-term SCRs as determined from the wave simulations for individual meteorological events, but no statistical correlation is found for wave height and SCRs over the long term. Despite the significantly higher rates of shoreline erosion over short time periods and from individual events like hurricanes, the cumulative impact over long time periods is low. Therefore, while the short-term response of these shorelines to episodic forcing should be taken into account in management plans, the long-term trends commonly used in ocean shoreline management can also be used to determine erosion setbacks on estuarine shorelines.

The effectiveness of beach mega-nourishment, assessed over three management epochs

Resilient coastal protection requires adaptive management strategies that build with nature to maintain long-term sustainability. With increasing pressures on shorelines from urbanisation, industrial growth, sea-level rise and changing storm climates soft approaches to coastal management are implemented to support natural habitats and maintain healthy coastal ecosystems. The impact of a beach mega-nourishment along a frontage of interactive natural and engineered systems that incorporate soft and hard defences is explored. A coastal evolution model is applied to simulate the impact of different hypothetical mega-nourishment interventions to assess their impacts’ over 3 shoreline management planning epochs: present-day (0–20 years), medium-term (20–50 years) and long-term (50–100 years). The impacts of the smaller interventions when appropriately positioned are found to be as effective as larger schemes, thus making them more cost-effective for present-day management. Over time the benefit from larger interventions becomes more noticeable, with multi-location schemes requiring a smaller initial nourishment to achieve at least the same benefit as that of a single-location scheme. While the longer-term impact of larger schemes reduces erosion across a frontage the short-term impact down drift of the scheme can lead to an increase in erosion as the natural sediment drift becomes interrupted. This research presents a transferable modelling tool to assess the impact of nourishment schemes for a variety of sedimentary shorelines and highlights both the positive and negative impact of beach mega-nourishment.

Economic evaluation of using marine dredged material for erosion control along the northeast coast of the Nile Delta, Egypt

The present study is the first attempt in Egypt to assess feasibility of using of dredging material from Damietta Harbor in the northwestern Nile Delta for erosion control. The study also provides an economic evaluation for the shoreline management alternatives selected to mitigate for the effects of coastal erosion at two pilot eroding areas (namely, A and B) located near the Damietta Harbor. Results of compatibility analysis reveal that the dredging material is fairly compatible with the native sand of the nearby eroding beaches. In addition to soft nourishment by dredged sand, other types of coastal engineering measures which are often used in erosion management area were also evaluated as alternatives for erosion control and mitigation solution. Economic feasibility assessment by means of cost-benefit analysis of direct and indirect items has been carried out to facilitate comparison between these alternatives. Analysis of alternatives has been also supported by other criteria to select the cost-effective and environmentally acceptable option to protect the eroding pilot areas. These criteria include the high total cost paid for maintenance of the Damietta Harbor channel with no use, anticipated impacts on the littoral system, sustainability, future plans for protection of the existing coastlines, and lessons learned from previous shore protection works in the Nile Delta. The final selection of the best viable alternative indicates that the procedure of beach nourishment is the most appropriate form for protection area A, while a combination of groins and sand nourishment is more relevant for area B. In any case, material dredged from the navigation approach of the Damietta Harbor should be utilized as a borrow material in the nourishment schemes and excluding use of the terrestrial sources.

Assessing Embayed Equilibrium State, Beach Rotation and Environmental Forcing Influences; Tenby Southwest Wales, UK

The morphological change of a headland bay beach—Tenby, West Wales, UK—was analysed over a 73-year period (1941–2014). Geo-referenced aerial photographs were used to extract shoreline positions which were subsequently compared with wave models based on storm event data. From the 1941 baseline, results showed shoreline change rates reduced over time with regression models enabling a prediction of shoreline equilibrium circa 2061. Further temporal analyses showed southern and central sector erosion and northern accretion, while models identified long-term plan-form rotation, i.e., a negative phase relationship between beach extremities and a change from negative to positive correlation within the more stable central sector. Models were then used in conjunction with an empirical 2nd order polynomial equation to predict the 2061 longshore equilibrium shoreline position under current environmental conditions. Results agreed with previous regional research which showed that dominant south and southwesterly wave regimes influence south to north longshore drift with counter drift generated by less dominant easterly regimes. The equilibrium shoreline was also used to underpin flood and inundation assessments, identifying areas at risk and strategies to increase resilience. UK shoreline management plans evaluate coastal vulnerability based upon temporal epochs of 20, 50 and 100 years. Therefore, this research evaluating datasets spanning 73 years has demonstrated the effectiveness of linear regression in integrating temporal and spatial consequences of sea level rise and storms. The developed models can be used to predict future shoreline positions aligned with shoreline management plan epochs and inform embayed beach shoreline assessments at local, regional and international scales, by identifying locations of vulnerability and enabling the development of management strategies to improve resilience under scenarios of sea level rise and climate change.

Challenges and Gaps in the Existing Laws and Policies in Marine Related Resource Use and Conservation in Watamu Mida Creek, Kenya

Having a comprehensive environmental legislative framework which assists laws and policy guidelines to be formulated and implemented are crucial for the management and conservation of coastal areas. Watamu Mida creek coastal area needs protection and special consideration because it is a very fragile environment which can be negatively affected if a proper management plan has not been put in place. The objective of this research is to assess challenges and gaps in the existing government laws, policies and regulations on land use, mangrove forest and shoreline management. In addition, the study also incorporates the opinion and knowledge of all local stakeholders who work and live in the area in order to triangulate what the problems are, and what needs to be done in future in order to come up with a more sustainable and practical management plan. A review of the available Acts and polices specifically regarding shoreline protection and mangrove conservation was undertaken highlighting the challenges of each mandated institution. For the household questionnaires, a stratified random sampling method was used. The household survey included 60 respondents from different resource users groups and villages. Five Focused Group Discussions (FGDs) were conducted with representatives of the community and eleven key informant interviews were conducted with the key leading government office representative’s, non-governmental organizations, hoteliers, and long term residents along the beach. The research found that the policy instrument review of the existing policy and legal framework indicated a number of gaps and opportunities for the protection of the coastal environment in the study area. Institutional mandates between the Kenya Forest Service and Kenya Wildlife Service need to be fully clarified with urgency, in order for the management plans for the area to be both approved and supported by these government agencies. In addition, policies and regulations which are not currently implemented need to be updated based on the current pressure-state situation, and there should be strong law enforcement and strict regulation and guidelines to protect this coastal environment.

The use of helophytes in assessing eutrophication of temperate lowland lakes: Added value?

Macrophyte-based methods for lake ecological status assessment universally include hydrophytes. Emergent plants (helophytes) are presumed to respond more directly to soil characteristics, wind exposure or shoreline management, hence are usually not considered as reliable indicators of water nutrient enrichment. The aims of the study were to explore the potential role of helophytes as eutrophication indicators and to test whether including or excluding emergent vegetation affects the indicator value of the Ecological State Macrophyte Index (ESMI) used in lake monitoring in Poland. Data on macrophyte composition and abundance (76 hydrophyte and 48 helophyte communities) and water quality from 490 Polish lowland lakes were analysed. Based on the frequency distribution and non-metric multi-dimensional scaling ordination, helophyte communities that exhibited clear trends of occurrence and abundance along the eutrophication gradient and enabled differentiation between lakes in diverse ecological conditions were identified. The effect of emergent vegetation on assessment metric diagnostic capacity was tested using modified index ESMI calculated with helophytes being included (CompESMITOT) and excluded (CompESMIHYDR) by comparing correlations between both metrics and eutrophication indicators (trophic state indices). Compared to CompESMITOT, CompESMIHYDR correlated slightly, though significantly weaker with most of the water quality indicators, and only for TSITP the difference in metric responses was statistically non-significant. The added diagnostic value of including emergent vegetation was between 0.04 and 0.08 of r2 increase and this benefit was more pronounced in more degraded lakes. The presented results demonstrated that emergent vegetation provides reliable information on ecosystem ecological conditions and can support assessment of the ecological status of lakes under eutrophication pressure.

Shoreline management plan for a mudbank dominated coast

Coastal processes along the Munambam to Chettuwa coastline located at the south-west part of India have been studied to understand the role of a mudbank and artificial structures like breakwaters in causing shoreline changes. The mudbank occurring along this coast is different from those in South America, Lousiana and China. The morphology and coastal processes of the coast have been studied by collecting nearshore and beach data from 2009 to 2013. Location of the mudbank area has been shifting over the years from north to south. The beach at the mudbank and its north is accreting while the southern side is eroding. Harbor breakwaters and seawalls are other factors influencing beach stability. An erosion hotspot along this mudbank coast is identified and management interventions proposed based on numerical model studies using MIKE 21 SW model and LITPACK. The model results are calibrated and validated with field observations. Sediment transport along this sector was estimated using LITDRIFT module. Shoreline change was calculated using the LITLINE module. The production run was carried out with different management options and the most suitable option is recommended for the eroding sector. The other sectors do not require any intervention to sustain the beaches.

Simulating mesoscale coastal evolution for decadal coastal management: A new framework integrating multiple, complementary modelling approaches

Coastal and shoreline management increasingly needs to consider morphological change occurring at decadal to centennial timescales, especially that related to climate change and sea-level rise. This requires the development of morphological models operating at a mesoscale, defined by time and length scales of the order 101 to 102years and 101 to 102km. So-called ‘reduced complexity’ models that represent critical processes at scales not much smaller than the primary scale of interest, and are regulated by capturing the critical feedbacks that govern landform behaviour, are proving effective as a means of exploring emergent coastal behaviour at a landscape scale. Such models tend to be computationally efficient and are thus easily applied within a probabilistic framework. At the same time, reductionist models, built upon a more detailed description of hydrodynamic and sediment transport processes, are capable of application at increasingly broad spatial and temporal scales. More qualitative modelling approaches are also emerging that can guide the development and deployment of quantitative models, and these can be supplemented by varied data-driven modelling approaches that can achieve new explanatory insights from observational datasets. Such disparate approaches have hitherto been pursued largely in isolation by mutually exclusive modelling communities. Brought together, they have the potential to facilitate a step change in our ability to simulate the evolution of coastal morphology at scales that are most relevant to managing erosion and flood risk. Here, we advocate and outline a new integrated modelling framework that deploys coupled mesoscale reduced complexity models, reductionist coastal area models, data-driven approaches, and qualitative conceptual models. Integration of these heterogeneous approaches gives rise to model compositions that can potentially resolve decadal- to centennial-scale behaviour of diverse coupled open coast, estuary and inner shelf settings. This vision is illustrated through an idealised composition of models for a ~70km stretch of the Suffolk coast, eastern England. A key advantage of model linking is that it allows a wide range of real-world situations to be simulated from a small set of model components. However, this process involves more than just the development of software that allows for flexible model coupling. The compatibility of radically different modelling assumptions remains to be carefully assessed and testing as well as evaluating uncertainties of models in composition are areas that require further attention.

Conceptualising and mapping coupled estuary, coast and inner shelf sediment systems

Whilst understanding and predicting the effects of coastal change are primarily modelling problems, it is essential that we have appropriate conceptual frameworks for (1) the formalisation of existing knowledge; (2) the formulation of relevant scientific questions and management issues; (3) the implementation and deployment of predictive models; and (4) meaningful engagement involvement of stakeholders. Important progress continues to be made on the modelling front, but our conceptual frameworks have not evolved at a similar pace. Accordingly, this paper presents a new approach that re-engages with formal systems analysis and provides a mesoscale geomorphological context within which the coastal management challenges of the 21st century can be more effectively addressed. Coastal and Estuarine System Mapping (CESM) is founded on an ontology of landforms and human interventions that is partly inspired by the coastal tract concept and its temporal hierarchy of sediment sharing systems, but places greater emphasis on a hierarchy of spatial scales. This extends from coastal regions, through landform complexes, to landforms, the morphological adjustment of which is constrained by diverse forms of human intervention. Crucially, CESM integrates open coastal environments with estuaries and relevant portions of the inner shelf that have previously been treated separately.In contrast to the nesting of littoral cells that has hitherto framed shoreline management planning, CESM charts a complex web of interactions, of which a sub-set of mass transfer pathways defines the sediment budget, and a multitude of human interventions constrains natural landform behaviour. Conducted within a geospatial framework, CESM constitutes a form of knowledge formalisation in which disparate sources of information (published research, imagery, mapping, raw data etc.) are generalised into usable knowledge. The resulting system maps provide a framework for the development and application of predictive models and a repository for the outputs they generate (not least, flux estimates for the major sediment system pathways). They also permit comparative analyses of the relative abundance of landforms and the multi-scale interactions between them. Finally, they articulate scientific understanding of the structure and function of complex geomorphological systems in a way that is transparent and accessible to diverse stakeholder audiences. As our models of mesoscale landform evolution increase in sophistication, CESM provides a platform for a more participatory approach to their application to coastal and estuarine management.

A short guide to doing nothing at the seaside

This paper focuses upon the new landscape of strategic coastal planning and implementation in England and Wales resulting from the development of shoreline management plans (SMPs) by flood and coastal erosion risk management (FCRM) authorities; the issues raised will be very familiar elsewhere in the world. The real test is how to implement the many measures and management decisions within these SMPs. In many cases, those decisions were difficult to reach; sometimes the result was an uneasy agreement to maintain defences indefinitely, if the funding is available; elsewhere, bold decisions were taken to withdraw maintenance using the ‘no active intervention’ SMP policy option. This policy is often paraphrased as ‘do nothing’, but in reality it is usually far from being a passive exercise. Depending on the circumstances and rationale for not intervening, it may entail a lot of work and have many implications. What is the nature of current intervention? Are there existing FCRM assets in place, and if so, will they be dismantled or left to disintegrate? Either way, potential impacts upon public health and safety, the natural environment, coastal processes, amenity and local communities and businesses need attention, and the exercise needs careful planning and engagement. There may be other options to consider, such as the ‘localisation’ or transfer of assets, and management of them, to third parties – but what are the liabilities associated with this and is it sustainable? A well-planned decommissioning of assets that is written into a SMP in advance is more likely to address these implications successfully, whereas a withdrawal from maintenance in the teeth of local opposition despite an original intention to defend may become complicated. The FCRM community needs to be prepared for these decisions and their consequences in advance. Additionally, is ‘no active intervention’ compliant with European law? The Environment Agency and the Department for Environment, Food and Rural Affairs are working with local authorities and other partners on a number of initiatives that will clarify issues, review experience and provide simple, practical guidance to risk management authorities faced with implementing a ‘no active intervention’ option. This paper will highlight the results and products of some of these initiatives and reflect more widely on the ‘deliverability’ of SMPs as they stand. ‘Doing nothing’ at the coast is clearly less relaxing than it sounds.

Human impacts on morphodynamic thresholds in estuarine systems

Many estuaries worldwide are modified, primarily driven by economic gain or safety. These works, combined with global climate changes heavily influence the morphologic development of estuaries. In this paper, we analyze the impact of human activities on the morphodynamic developments of the Scheldt Estuary and the Wadden Sea basins in the Netherlands and the Yangtze Estuary in China at various spatial scales, and identify mechanisms responsible for their change. Human activities in these systems include engineering works and dredging activities for improving and maintaining the navigation channels, engineering works for flood protection, and shoreline management activities such as land reclamations. The Yangtze Estuary is influenced by human activities in the upstream river basin as well, especially through the construction of many dams. The tidal basins in the Netherlands are also influenced by human activities along the adjacent coasts. Furthermore, all these systems are influenced by global changes through (accelerated) sea-level rise and changing weather patterns. We show that the cumulative impacts of these human activities and global changes may lead to exceeding thresholds beyond which the morphology of the tidal basins significantly changes, and loses its natural characteristics. A threshold is called tipping point when the changes are even irreversible. Knowledge on such thresholds or tipping points is important for the sustainable management of these systems. We have identified and quantified various examples of such thresholds and/or tipping points for the morphodynamic developments at various spatial and temporal scales. At the largest scale (mega-scale) we consider the sediment budget of a tidal basin as a whole. A smaller scale (macro-scale) is the development of channel structures in an estuary, especially the development of two competing channels. At the smallest scale (meso-scale) we analyze the developments of tidal flats and the connecting channels.

Towards Effective Public Consultation and Participation in Nigeria: Lessons from Shoreline Management Plans (SMPs) Activities in England

This paper examines the shoreline management planning policy in England and its suitability for ameliorating the diverse environmental problems associated with Nigeria’s coastal zones. It examines the success of SMPs in England since the mid-1990s and progress achieved, with the aim of understudying the current management approach that can be transferred to Nigeria to strengthen its adoption, and as a necessary corollary, implementation of the SMPs. This paper also examines key elements of the shoreline management frameworks in England and provides answers to the question: Would shoreline management planning approach in England be appropriate and feasible in Nigeria? It further concludes that many of the action plans and principles of participation should be adoptable provided that a participatory approach that involves all stakeholders including community members and relevant sectoral ministries as well as appropriate legal framework is encouraged.

Valuation of the ecosystem services of beach nourishment in decision-making: The case study of Tarquinia Lido, Italy

Cost Benefit Analysis (CBA) is a systematic process commonly employed by the US Army Corps of Engineers (USACE) to assess primarily benefits stemming from storm damage reduction and recreation enhancement by beach protection. The USACE goal is to quantify federal money disbursement to local communities to counter the consequences of coastal erosion. The EU has recommended the use of CBA for shoreline management (both at regional and local scales), looking not only at the financial aspects of project assessment, but also at non-market benefits (ecosystem services of the beaches) and environmental costs, assessed on a broad time horizon in a given sediment cell. In this paper, several ecosystem services provided by beach protection are considered and some of them monetised to assess the local net benefits of a nourishment project carried out along the Tyrrhenian coast of Italy. The paper shows that free riding emerges by the public supply of coastal protection, and that it could be possibly partially removed charging the cost of beach maintenance to the local users. In addition, supply of coastal protection may generate negative environmental externalities. However, costs of environmental damage of the beach nourishment are not easy to be internalised. This suggests alternative market mechanisms (charges or insurance premiums) to reduce the development pressure on coastal areas subject to high rates of erosion or to explore the adoption of subsides such as payments for ecosystem services (PES) at seascape scales.

Insights into the establishment of the Manila clam on a tidal flat at the southern end of an introduced range in Southern California, USA.

Coastal ecosystem modifications have contributed to the spread of introduced species through alterations of historic disturbance regimes and resource availability, and increased propagule pressure. Frequency of occurrence of the Manila clam (Venerupis phillipinarum, Veneridae) in Southern California estuaries has increased from absent or sparse to common since the mid-1990s. Potential invasion vectors include seafood sales and aquaculture, and spread from established northern populations over decades. The clam’s post-settlement habitat preferences are, however, uncertain in this region. Our project aimed to identify factors associated with established patches of the clam within a bay toward the southern end of this introduced range. During summer 2013, we sampled 10 tidal flat sites in Mission Bay, San Diego; each containing an area with and without hard structure (e.g., riprap, boulders). We measured likely environmental influences (e.g., sediment variables, distance to ocean). Manila clam densities across the bay were most strongly associated with site, where highest densities were located in the northern and/or back halves of the bay; and weakly correlated with lower porewater salinities. Within sites, Manila clam density was enhanced in the presence of hard structure in most sites. Prevailing currents and salinity regimes likely contribute to bay wide distributions, while hard structures may provide suitable microhabitats (refuge from predators and physical stress) and larval entrapment within sites. Results provide insights into decisions about future shoreline management efforts. Finally, we identify directions for future study to better understand and therefore predict patterns of establishment of the Manila clam in the southern portion of its introduced range.

Managing coastal erosion hotspots along the Elmina, Cape Coast and Moree area of Ghana

Like most coastlines the world over, Ghana's coast has been receding, requiring management interventions to protect coastal communities and assets of national importance. In order to adopt sound management interventions that would have a long lasting positive impact on the coastal zone, an understanding of the historic pattern of coastline change and coastal dynamics is required. This paper presents an analysis of the historic trends in coastline changes along the Elmina, Cape Coast and Moree area of Ghana using three shoreline data that spans a period of 38 years using ArcGIS and Digital Shoreline Analysis System tools. The study found that the Elmina, Cape Coast and Moree area had been eroding at a rate of 1.22 m/year ± 0.16 m from 1974 to 2012. It was identified that the widespread practice of beach sand mining in the area has significantly contributed to the erosion of several sections of the coastline. The study also identified the lack of an existing coastline management plan for Ghana's coast as the reason for the poor coastal erosion management techniques often used by coastal managers in response to the threat of coastal erosion, which eventually causes an acceleration of local erosion rates. The study finally makes a case for the adoption of a proactive and coordinated coastline management plan for Ghana's coast similar to that of the United Kingdom shoreline management plans because of the numerous known advantages.

Sand Dynamics as a Tool for Coastal Erosion Management: A Case Study in Darwin Harbour, Northern Territory, Australia

Darwin Harbour, Northern Territory, Australia, is a semi diurnal macro-tidal embayment that is situated in a cyclone prone area. The tidal variations range up to 8 m with a mean tidal range of 3.7 m. The coastal area consists of mangrove fringes, sandy beaches, tidal flats, rocky shore platforms and coastal cliffs. The main morphological changes are movement of the sandbars and erosion of beaches and coastal cliffs. Sea level rise due to climate change and more intense cyclones and storm surges may exacerbate these processes with detrimental impacts on the coast and the adjacent city, particularly when occurring at high tide. To assist with coastal erosion management, a greater understanding of morphological changes is required. A two-dimensional depth averaged finite-element hydrodynamic model (RMA-2), coupled with a sediment transport model (RMA-11) from Resource Modelling Associates, have been used to deduce the sources and spatial patterns of sand erosion and deposition in the harbour. Geochemical analysis is also used to characterize the sand source(s). This paper presents hydrodynamic simulations focusing on culturally and recreationally significant beaches in Fannie Bay. Simulations indicate that the Cullen Bay sandbar is an indirect sand source replenishing Fannie Bay beaches. Respective geochemical results also show similar Rare Earth Element contents of the sand in the area. Considering the fast pace of development in and around Darwin Harbour, this study is essential in providing a fundamental understanding of coastal processes and to assist coastal and shoreline management in a tropical estuary.