Coastal Scientists Research Articles

Aboveground allometric models for freeze-affected black mangroves (Avicennia germinans): equations for a climate sensitive mangrove-marsh ecotone.

Across the globe, species distributions are changing in response to climate change and land use change. In parts of the southeastern United States, climate change is expected to result in the poleward range expansion of black mangroves (Avicennia germinans) at the expense of some salt marsh vegetation. The morphology of A. germinans at its northern range limit is more shrub-like than in tropical climes in part due to the aboveground structural damage and vigorous multi-stem regrowth triggered by extreme winter temperatures. In this study, we developed aboveground allometric equations for freeze-affected black mangroves which can be used to quantify: (1) total aboveground biomass; (2) leaf biomass; (3) stem plus branch biomass; and (4) leaf area. Plant volume (i.e., a combination of crown area and plant height) was selected as the optimal predictor of the four response variables. We expect that our simple measurements and equations can be adapted for use in other mangrove ecosystems located in abiotic settings that result in mangrove individuals with dwarf or shrub-like morphologies including oligotrophic and arid environments. Many important ecological functions and services are affected by changes in coastal wetland plant community structure and productivity including carbon storage, nutrient cycling, coastal protection, recreation, fish and avian habitat, and ecosystem response to sea level rise and extreme climatic events. Coastal scientists in the southeastern United States can use the identified allometric equations, in combination with easily obtained and non-destructive plant volume measurements, to better quantify and monitor ecological change within the dynamic, climate sensitive, and highly-productive mangrove-marsh ecotone.

Briefing: Young Coastal Scientists and Engineers Conference 2013

On 25–26 March 2013, 52 early career scientists and engineers, studying various aspects of coastal science, met at the University of Aberdeen for the ninth Young Coastal Scientists and Engineers Conference. The conference was jointly organised by the School of Engineering, University of Aberdeen, and Marine Scotland Science. Early-career scientists, researchers and practitioners presented 23 oral and 17 poster presentations over the 2-day meeting. The papers all had a coastal theme with a large diversity in the subjects covered, including waves, currents, tidal energy, coastal erosion, sediment transport, fluid mechanics and particle tracking. This briefing paper reports on the conference, and presents the keynote lecture and four papers voted to be of especially high quality by the panel of judges.

Salt marshes

Salt marshes are unique ecosystems that are brimming with diversity, and provide crucial shelter to coastal communities.

Evaluation of storm impact on sandy beaches of the Gulf of Valencia using Landsat imagery series

The impact of storms on sandy beaches and the subsequent recovery process is described from an analysis of the shoreline positions obtained from Landsat 5 TM and Landsat 7 ETM+ imagery. Shoreline extraction is based on an algorithm previously proposed by the authors that enables a positioning accuracy of 5m root mean square error (RMSE). The impact of six storms registered over a period of seven months (between November 2001 and May 2002) and the beach recovery processes until December 2002 across a 100km segment of the Gulf of Valencia on the Spanish Mediterranean coast were analysed by comparing 12 shoreline positions. The multiple shoreline positions obtained from Landsat images provide very useful information for describing the impact of storms and the recovery process across large segments of microtidal coast. This enables the identification of differences not only in the magnitude of change produced by a particular event but also in the cumulative effect associated with several storm events, and in the study of how the beach recovery process takes place. The results show a high level of spatial variability. Beaches with steep slopes experienced fewer changes than shallow slopes. The existence of well developed foredunes in some areas minimised the reduction in the beach width after the storms. Coastal orientation was another important factor in explaining storm impact and the recovery process. This factor affects not only the way the waves interact with the beaches but also the sediment longshore transport: beach regeneration is slower when the transport of sediments is limited by artificial infrastructures (groins, jetties, ports) or natural sediment traps (headlands). The main limitations of using the proposed methodology to obtain the shoreline position from Landsat images are related to: (i) the precision in the shoreline detection; (ii) the nature of the indicator obtained, that is, the water/land interface; and (iii) the registration instant defined by the image acquisition time. However, the high frequency of the data acquisition and the possibility to cover large coastal areas bring a new perspective that enriches other methods and tools used by coastal scientists.

Correlating Storm Surge Heights with Tropical Cyclone Winds at and before Landfall

Abstract This paper investigates relationships between storm surge heights and tropical cyclone wind speeds at 3-h increments preceding landfall. A unique dataset containing hourly tropical cyclone position and wind speed is used in conjunction with a comprehensive storm surge dataset that provides maximum water levels for 189 surge events along the U.S. Gulf Coast from 1880 to 2011. A landfall/surge classification was developed for analyzing the relationship between surge magnitudes and prelandfall winds. Ten of the landfall/surge event types provided useable data, producing 117 wind–surge events that were incorporated into this study. Statistical analysis indicates that storm surge heights correlate better with prelandfall tropical cyclone winds than with wind speeds at landfall. Wind speeds 18 h before landfall correlated best with surge heights. Raising wind speeds to exponential powers produced the best wind–surge fit. Higher wind–surge correlations were found when testing a more recent sample of data that contained 63 wind–surge events since 1960. The highest correlation for these data was found when wind speeds 18 h before landfall were raised to a power of 2.2, which provided R2 values that approached 0.70. The R2 values at landfall for these same data were only 0.44. Such results will be useful to storm surge modelers, coastal scientists, and emergency management personnel, especially when tropical cyclones rapidly strengthen or weaken while approaching the coast.

Shoreline changes in response to sea level rise along Digha Coast, Eastern India: an analytical approach of remote sensing, GIS and statistical techniques

Shoreline is one of the rapidly changing linear features of the coastal zone which is dynamic in nature. The issue of shoreline changes due to sea level rise over the next century has increasingly become a major social, economic and environmental concern to a large number of countries along the coast, where it poses a serious problem to the environment and human settlements. As a consequence, some coastal scientists have advocated analyzing and predicting coastal changes on a more local scale. The present study demonstrates the potential of remote sensing, geospatial and statistical techniques for monitoring the shoreline changes and sea level rise along Digha coast, the eastern India. In the present study, multi-resolution and multi temporal satellite images of Landsat have been utilized to demarcate shoreline positions during 1972, 1980, 1990, 2000, and 2010. The statistical techniques, linear regression, end-point rate and regression coefficient (R2) have been used to find out the shoreline change rates and sea level change during the periods of 1972–2010. Monthly and annual mean sea level data for three nearby station viz., Haldia, Paradip and Gangra from 1972 to 2006 have been used to this study. Finally, an attempt has been made to find out interactive relationship between the sea level rise and shoreline change of the study area. The results of the present study show that combined use of satellite imagery, sea level data and statistical methods can be a reliable method in correlating shoreline changes with sea level rise.

Understanding the Controls on Storm Surge through the Building of a National Storm Surge Database

ABSTRACT Peek, K.M. and Young, R.S., 2013. Understanding the controls on storm surge through the building of a national storm surge database. The Program for the Study of Developed Shorelines at Western Carolina University (WCU) is using relational tools (Microsoft Access) and a geographic information system (ArcGIS) to build a national storm surge database. The database is comprehensive, queriable, and will provide one central location for coastal scientists, engineers, and the general public to access storm surge and high water-mark data. The national database currently contains over 5800 storm surge data points from 42 hurricanes. Detailed geo-referenced storm characteristics from the National Ocean and Atmospheric Administration's International Best Track Archive for Climate Stewardship are also part of the database and include storm track, wind speed, central pressure, and storm diameter. This allows the database to be queried to match storm characteristics with the surge generated. Analysis of the d...

Briefing: Young Coastal Scientists and Engineers Conference 2012

The 24 papers and posters presented at the eighth Young Coastal Scientists and Engineers Conference held at Bangor University in April 2012 were of a high standard, typical of that expected at a leading international conference. They gave a good indication of the breadth of basic and applied research currently being pursued in UK universities and consultancies. Papers covered a wide range of topics, including coastal management, shelf sea turbulence, renewable energy, cliff erosion, sediment transport, morphological modelling, nutrient and pollution transport, and scour protection, to mention but a few. This briefing reproduces the abstracts of the two Keynote lectures and of three presentations judged by the organising committee to be of particular merit. The next UK Young Coastal Scientists and Engineers Conference will be organised by Marine Scotland in Aberdeen in spring 2013.

Shoreline variations and coastal dynamics: A space–time data analysis of the Jonian littoral, Italy

Morphological variations of coastlines are caused by several key processes that are influenced by climate conditions, sea level variations, wave energy, tectonics and human-induced phenomena. These processes affect the dynamics of catchment basins and the coastal environment. Since the second half of the 20th century, the Jonian coast of the Basilicata Region (Italy) has witnessed a widespread retreating phenomenon, predominantly due to anthropogenic causes affecting transport processes along the riverbeds and causing reductions in the sediment supply to the coast. The disturbance in the balance between sediment transport carried out by the sea and the sediment supply performed by rivers has led to a deficit in the sediment budget. To understand the morphological dynamics of the littoral environment and quantify the amount of coastal erosion, an analysis of coastline change has been carried out using various data sources: historical cartography, aerial photographs and GPS surveys. Between 1870 and 1954, the 32-km-long Jonian littoral under examination showed an accretion trend, while the loss in beach surface steadily increased between 1954 and 2005. The average change in beach surface has been calculated as about +55,000 m2/yr (accretion) between 1870 and 1954 and −16,500 m2/yr (erosion) between 1954 and 2005. Overall, 640,000 m2 of sandy beaches were lost along the entire Jonian coast of the Basilicata Region between 1954 and 2005. Comparing the shoreline between 1870 and 1954, the average net shoreline movement (NSM) is +110 m vs. −30 m between 1954 and 2005. This analysis approach has proven to be effective in quantifying the erosion phenomenon and its effects, despite the lack of homogeneous data series and the variety of spatial and temporal scales over which coastal evolution occurs. The study represents an important step in understanding coastal dynamics in this region. As coastal areas are being affected by an increasing number of population and socio-economic activities, identification of shoreline changes and forecasts of coastline evolution represent key information for coastal scientists, engineers, decision makers and stakeholders for both the management of and development of future plans for coastal environments and for reducing exposure risk to coastal erosion.

THE MODIFIED COASTAL STORM IMPULSE (COSI) PARAMETER AND QUANTIFICATION OF FRAGILITY CURVES FOR COASTAL DESIGN

A coastal storm-strength parameter, the Coastal Storm Impulse (COSI) parameter was introduced at the ICCE 2006 (San Diego) and further discussed in the ICCE 2008 (Hamburg) and ICCE 2010 (Shanghai) proceedings. COSI is based on the conservation of linear, horizontal momentum to combine storm surge, wave dynamics, and currents over the storm duration. Both tropical storms (hurricanes) and extra-tropical storms (low-pressure fronts) can produce similar COSI parameters. Analysis of coastal storms over a 10 year period (1994-2003) of measured data at the Corps of Engineers, Field Research Facility (FRF), Duck, NC showed the need to modify the original method to (1) use the mean, nonlinear wave momentum flux, and (2) use only the spikes in storm surge when elevated water levels are above the mean high water level of the tide. This paper presents the full details of how to calculate the modified COSI parameter; the modified results for the 10-yr Duck data set and suggest possible applications to develop fragility curves for coastal engineering design. Clearly, fragility curves are needed to quantify risk and hence resilience in coastal systems design. The intensity of the "load† or "disturbance†, i.e. the severity of the coastal storm must be quantified to develop fragility curves. Excess water levels (storm surge), wave conditions (height, period, direction) and storm duration all contribute to the intensity of a coastal storm. How to combine these three factors has long been a concern of coastal scientists and engineers.

Scientists’ prioritization of global coastal research questions

Abstract Complex coastal management challenges often span ecological and political boundaries, and involve competing demands from groups advocating alternative coastal management strategies. As a consequence, policy-makers require scientific evidence from across a range of disciplines. Implementing cross-disciplinary research and facilitating science-policy engagement are, however, a significant challenge in its own right. Seven recent ecologically oriented ‘big question’ exercises identified a variety of research questions potentially important for coastal and marine management. In this research, 592 coastal scientists from 91 different countries completed a survey that ranked those 20 coastally oriented research questions. There was a clear overall ordering of aggregated coastal research priorities but scientists did exhibit heterogeneity regarding priorities. Some prioritized ecological issues while others focused more on issues such as coastal resource use or global environmental change. The differences in opinion were largely disciplinary-based, highlighting the importance of, and challenges in, encouraging scientific collaboration across disciplines to support effective coastal zone management. In addition to the ranking of existing questions, scientists submitted an additional 340 potential priority research questions, thus broadening the participatory nature of the original exercises. New questions regarding coastal processes, contaminants and pollution, and monitoring were prominent. This first synthesis across ‘big question’ exercises should provide valuable insights into the diversity of scientists’ opinions and help policy makers understand potentially conflicting science advice.

On the Continued Cost of Upkeep Related to Groins and Jetties

Abstract Pietrafesa, L.J., 2012. On the continued cost of upkeep related to groins and jetties. So-called terminal groins, which are actually jetties at the terminus of barrier islands where inlets are located, have been the subject of controversy for half a century in North Carolina. Coastal scientists have opposed these hardened structures and point to their destructive effects upon downstream beaches, requiring ever increasing and costly beach renourishment projects. Meanwhile, some coastal engineers have claimed that they can be used to “stabilize” migrating inlets. Local politicians, in response to real estate interests, have argued for the construction of the hardened structures and, in contrast to the claims of the scientists on the ground, have cited examples of success in North Carolina and at other locales on the U.S. eastern seaboard. So what are the facts? This Editorial presents the documented facts for North Carolina and the other U.S. east coast locales.

Sea-level rise and coastal change: the past as a guide to the future

There is a broader awareness than ever that we live in a changing environment. The spectre of climate change is of wide concern, and the observed trends and anticipated consequences of an acceleration of sea-level rise pose a series of threats for the future of people who live in coastal communities. Coastal geoscientists are able to reconstruct the position of former sea levels; they can also explain much of the geographical variation in relative sea-level history. Successive collaborative projects (many under the auspices of international programmes sponsored by IGCP and INQUA) derived local sea-level histories and compiled atlases of relative sea-level curves, and some addressed past coastal behaviour in response to these changes. The most recent International Geological Correlation programme project 588, ‘Preparing for coastal change’, continues this impressive lineage of projects that have laid the foundations for our understanding of sea-level behaviour over the late Quaternary. Today, these issues are a major focus in the debate about climate change, its impacts, and the need for adaptation on the most vulnerable shorelines. There is clearly a role for the palaeoenvironmental skillset honed through successive geoscientific projects. Investigations of past coastal environments have provided the tools for delineating past levels of the sea, but the stratigraphical and geochronological studies which were necessary to reconstruct the sea-level position also provide insights into where the shoreline lay and how the coast behaved as sea level changed. If the present is the key to the past, then the past, seen from the context of the present, can be a guide to the future. Collaborative projects and international co-operation between scientists from different disciplines can play important roles in future debates about how our world will change. First, the lessons learnt about the patterns of variation of relative sea level need to be more widely recognised by climate scientists. Efforts aimed at establishing the rate of future global sea-level rise need to be complemented by protocols to determine regional deviations from that mean rate of sea-level change. Second, modes of coastal change need to be identified to replace simplistic heuristics of coastal response, such as the Bruun rule. Simulation modelling offers a suite of tools that appear to give coastal managers guidance, but geoscientists should strive to produce evidence that can be used to develop and validate model behaviour. Coastal scientists presently have a relatively good understanding of coastal behaviour at millennial timescales, and process operation at contemporary timescales. However, there is less certainty about how coasts change on decadal to century timescales. It is these latter timescales which are particularly important for managers and policy-makers. These, and related challenges, provide a focus for research that will have a relevance for society that the coastal geoscience research community has rarely experienced.

Briefing: Young Coastal Scientists and Engineers Conference 2011

The 7th UK Young Coastal Scientists and Engineers Conference welcomed 60 scientists and engineers to come together and discuss coastal research. The conference was hosted by the National Oceanography Centre in Liverpool, 30–31 March 2011. Early career practitioners and researchers presented 42 short papers on a range of topics driven by current issues addressed by UK universities, government agencies and consultancies. Although all presentations had a coastal theme, content varied from small-scale processes to regional-scale monitoring and management, covering topics such as structure impact, sediment transport, morphology, waves, currents, ecology, oxygen, estuarine systems, stratification, modelling, observation, ice, renewables and extreme events. This paper presents the keynote lecture and six abstracts considered to be of particular merit by the panel of judges. The conference continues to travel the UK and will be held at Bangor University in 2012.

A storm surge database for the US Gulf Coast

AbstractTropical cyclone‐generated storm surges are among the most deadly and costly natural disasters to impact the United States. Unfortunately, no comprehensive storm surge dataset provides reliable, historical storm surge information for the United States. This paper introduces SURGEDAT, the first comprehensive surge database for the US Gulf Coast. SURGEDAT identifies the location and height of peak storm surge for 195 surge events since 1880. A total of 62 sources were utilized to construct this dataset, including 28 Federal Government sources, numerous academic publications, and more than 3000 pages of newspaper from 16 daily periodicals. Surge heights in this database range from Hurricane Katrina's 8.47 m surge to 1.22 m surges generated by 20 separate events. Spatial analysis reveals enhanced surge magnitudes and frequencies along the Central and Western Gulf Coast, as well as the Florida Keys, while reduced levels of surge activity were observed along the eastern Florida Panhandle and the West Coast of Florida. The methods utilized to create this database are thoroughly documented, a table provides the comprehensive list of surges, and a map provides the spatial distribution of peak surge events. SURGEDAT will be valuable to coastal stakeholders, including planners and emergency managers, coastal scientists, and the hurricane and storm surge research communities. Copyright © 2011 Royal Meteorological Society

Salt Marshes as Potential Indicators of Global Climate Change

Coastal scientists postulate that salt marshes are significantly affected by dynamics of global climate. However, few studies have explicitly proposed a perspective that regards salt marshes as potential indicators of climate change. This review article evaluates the possibility of salt marshes as indicators of global climate change, focusing upon three major aspects: sedimentary, vegetation, and biogeochemical dynamics. The previous literature concerned with these aspects commonly argues that the primary impact of climate change on salt marshes occurs via sea-level variations, because hydrologic fluctuations regulate the frequency, duration, and depth of over-marsh flooding events. Sedimentary, floristic, and biogeochemical dynamics prove to be significantly influenced by sea-level changes regardless of climate zones, and hence, undoubtedly possess a potential for indicating climate signatures. However, where plant-plant interactions such as facilitation and competition are important, vegetation dynamics in salt marshes may not be an immediate, sole function of sea-level and climate variations. Also, specifically in the field of salt marsh biogeochemistry, enough long-term data have not been collected to convincingly conclude that biogeochemistry is a useful indicator of climate change. Therefore, while this review is concerned mainly with the possibility of salt marshes as indicators of climate change, their suitability or usefulness is a different matter to be resolved through further data collection and discussion in future investigations.

Briefing: Young Coastal Scientists and Engineers Conference 2010

The 33 papers and posters presented at the sixth Young Coastal Scientists and Engineers Conference held at University College London in March 2010 were of a high standard, typical of that expected at a leading international conference. They gave a good indication of the breadth of basic and applied research currently being pursued in UK universities and consultancies. Topics included coastal management, dunes, saltmarshes, beaches, swash, renewable energy, gravity-driven currents, freak waves, sediment transport, morphological modelling, nutrient and pollution transport, scour protection, liquefied natural gas facilities and submerged breakwaters. The paper below reproduces the abstracts of the keynote Peregrine Lecture and of five presentations judged by the organising committee to be of particular merit. The next UK Young Coastal Scientists and Engineers Conference will be held at the National Oceanography Centre in Liverpool and is scheduled for 30–31 March 2011.

Five Questions on the Spill

Sizing up the weeks-long spill in the Gulf of Mexico and its impacts is proving a challenge for marine and coastal scientists. Scientists will be trying to answer five key questions over the coming months and years.

Shoreline Evolution and Management of Hawke's Bay, New Zealand: Tectonics, Coastal Processes, and Human Impacts

The evolution of the coast of Hawke's Bay, New Zealand, and its erosion problems have been governed by multiple factors, including its tectonic setting with an earthquake in 1931 that altered land elevations along its shore, ranging from a 2-m uplift at its north end to 1-m subsidence at its south. Human environmental impacts have also been important, including the deforestation of the watersheds of rivers and the mining of gravel and sand from their channels, having decreased the sediment supplies to the beaches. Significant erosion has occurred at the south end of the Hawke's Bay shore, attributed in part to its subsidence in 1931, together with the net northward longshore transport of the beach sediment that is greater than the volumes being supplied by the rivers, the beach-sediment budget being significantly “in the red.” Midway along the Bay's shore, the construction of the Port of Napier's breakwater in 1887–90, extending seaward from the Buff Hill headland within that city, is interpreted by some investigators to have been the cause of the erosion experienced at Westshore, a development located immediately north of the breakwater. The assumption has been that this erosion was the result of the breakwater having blocked the northward longshore transport of sediment that formerly had bypassed Bluff Hill, this being an example of down-drift beach erosion. However, a reexamination of the history of the Port's development, the resulting shoreline changes, differences in beach gravels on the shores north and south of Bluff Hill, as well as other evidence, support the conclusion that the breakwater was not the cause of the erosion; instead, the impacts to Westshore at the time of the breakwater construction can be attributed primarily to a series of major storms, which produced erosion at a number of sites along the Hawke's Bay shore. There has been minimal erosion at Westshore since the completion of the breakwater a century ago, its northward extending arm acting to shelter the development from the waves of major storms. Investigations by coastal scientists and engineers of the Hawke's Bay coast, together with a comprehensive beach-survey monitoring program, support its sound management based on an understanding of the multiple factors that are important to its responses during storms, and to its long-term changes.

Static bay beach concept for scientists and engineers: A review

Headland-bay beach (HBB) is one of the most prominent physiographic features on the oceanic margin of many countries in the world. Under the influence of a predominant swell, its curved periphery in natural environment may reach static equilibrium and remains stable without sediment supply from updrift and/or a riverain source within its own embayment. Coastal scientists and engineers have attempted to develop mathematical expressions to quantify this ideal bay shape since the 1940s. As the scenario with depleting sediment supply has become a common reality on many parts of the world coastline in more recent time, some coastal engineers have advocated a rational approach to mimicking the static bay shape found in nature in order to mitigate beach erosion as well as for coastal management. Nowadays, many useful applications have emerged since the publication of the parabolic bay shape equation (PBSE) developed for static equilibrium planform (SEP) in late 1980s. The advance in modern computer technologies and international collaboration has further facilitated the exchange of knowledge and applications of this static bay beach concept (SBBC). This paper reviews the progress on the research in HBB made by geographers and geologists since the 1940s, together with the involvement of coastal engineers working on shore protection and management from the 1960s. Aided by software MEPBAY developed in 2003 for the PBSE, several practical examples are demonstrated in this paper for the stability verification of natural and man-made bay beaches, shore protection, mitigating downdrift erosion of a harbour, design of recreational bay beach, as well as for environmental impact assessment. Limitations on and clarifications for engineering applications based on the SBBC are also discussed in this paper.