Shoreline Erosion Rates Research Articles

Shoreline change analysis and erosion prediction using historical data of Kuala Terengganu, Malaysia

At the present time, coastal changes are having a major impact in many regions of the world. Relative sea-level rise would significantly contribute to physical changes in coastal cities. Predicting the magnitude of coastal changes such as erosion and land loss is essential for a better understanding of the impacts on environment and coastal communities, as well as for management, planning and protection in coastal areas. An increase in the rate of sea-level rise and range of potential impacts, including flood and coastal erosion, will likely affect the wide East Coast of Peninsular Malaysia and would cause serious disturbance for sandy beaches, particularly in Kuala Terengganu. This study attempts to predict the future erosion in the coastal area of Kuala Terengganu, Malaysia. The shoreline erosion as a result of sea-level rise was predicted using the Bruun Rule. This is the best known model that provides a rate of shoreline erosion under sea-level rise for sandy beaches. The result of Bruun Model is analysed and presented in a Geographic Information System (GIS). Results indicate an upward trend in the future for erosion in this coastal area. The highest erosion rate is 3.20 m/year and the most sensitive zones are expected to be around Universiti Malaysia Terengganu (UMT) and left bank of Kuala Terengganu from 2015 to 2020. It also can provide the basic information that decision makers need when they are planning any new activity within the coastal area.

Assessment of coastal vulnerability to multi-hazardous events using geospatial techniques along the eastern coast of Bangladesh

The eastern coastal region of Bangladesh, which has a 377 km-long coastline, is highly vulnerable to multi-hazardous events, such as tropical cyclones, coastal floods, coastal erosion and salinity intrusion. The vulnerability of this coastal region is likely to increase under the future climate change context. This research aims to develop a coastal vulnerability index (CVI) of multi-hazardous events for the eastern coastal region of Bangladesh. Eight parameters, mostly focused on physical vulnerability, were considered in this study. Various thematic layers were prepared for each parameter using spatial techniques, and all parameters were assigned a vulnerability ranking. Finally, a CVI was developed and the related values were categorised into five distinct classes (i.e., very high, high, moderate, low, and very low). Results indicate that approximately 121 km (32%) of the coastline of the study area is in high-to very high-vulnerability zones. Low elevations, gentle slopes, high storm surge impacts, sandy coastlines, high shoreline erosion rates and high sea-level changes are the most important factors of high to very-high vulnerability zones. The moderately vulnerable area covers approximately 119 km (32%) of the coastline. Meanwhile, 78 (21%) and 59 (16%) km of the coastlines are in low-to very low-vulnerability zones, respectively. These coastlines are characterised by steep slopes with high elevations, low tide range and storm surge heights as well as less erosion. The CVI results were validated by qualitative observations acquired from the field. The findings of this study can be applied by policymakers and administrators to develop effective mitigation plans and minimise the likely impacts of coastal multi-hazards.

Legacy effects of Hurricane Katrina influenced marsh shoreline erosion following the Deepwater Horizon oil spill

Disturbance interactions occur when one perturbation influences the severity and perhaps the baseline state of succeeding disturbances. Natural and anthropogenic disturbances are frequent in dynamic coastal ecosystems and can often be linked. We evaluated potential for disturbance interactions associated with the 2010 Deepwater Horizon (DWH) oil spill, which was preceded by disturbance from Hurricane Katrina in 2005, by quantifying marsh shoreline retreat across both events. Our goal was to determine the degree to which Hurricane Katrina altered baseline rates of erosion prior to the DWH spill. We quantified erosion rate and fetch from aerial images of northern Barataria Bay, Louisiana marsh shorelines classified as reference, moderately-oiled, and heavily-oiled over three pre-spill time periods (1998–2004, prior to Hurricane Katrina; 2004–2005, during Katrina; 2005–2010, post-Katrina but pre-oil spill) and a post-spill period from 2010 to 2013. Prior to Hurricane Katrina, marsh shoreline erosion rates were low (from 0.38 to 1.10 m yr−1). In contrast during Hurricane Katrina (2004–2005), erosion increased by 661% and 756%, respectively, for shorelines that would subsequently become moderately and heavily-oiled; reference shoreline erosion increased by 59%. These high erosion rates were associated with increased fetch and higher wave action due to loss of protective geomorphic features such as small islands and spits and persisted during the post-Katrina/pre-spill period of 2005–2010 (0.62, 1.38, and 2.07 m yr−1 for reference, moderately, and heavily-oiled shorelines, respectively). Erosion rates increased modestly after the DWH event (reference = 1.13 m yr−1, moderate oiling = 1.45 m yr−1; heavy oiling = 2.77 m yr−1), but not significantly, compared to the post-Katrina period. Consequently, we could not detect a post-spill increase in marsh shoreline erosion. Rather, we concluded that Hurricane Katrina reset the erosion baseline, thereby connecting the two disturbances, and was the major driver of marsh shoreline erosion at our research sites during the study period.

The impact of land used changes on mangrove forest and shoreline dynamic in Muara Gembong, Bekasi, West Java

Muara Gembong used to a large area of mangroves at the northern tip of Bekasi Regency, West Java. Over the last 4 decades, this area has experienced significant changes in land use and loss of environmental and ecosystem services provided by mangroves. Past economic activities have resulted in the conversion of thousands of hectares of mangrove into pond areas in pursuit of fisheries production, which at the time became a national program. This change has resulted in ecological disasters and caused economic losses to coastal communities such as shoreline changes (causing the loss of several coastal villages) and sea water intrusion (damaging pond areas and resulting crop failure). This study assessed the impact of land used changes on mangrove dynamic and shoreline erosion rate along the 5 coastal villages of Muara Gembong over 42 years. Multi-temporal Landsat data set and ground truth survey were applied. The imageries have been classified digitally using Maximum Likelihood Classification (MLC) algorithm and have been validated through the process of accuracy assessment. Digital Shoreline Analysis System (DSAS) in ArcGIS environment was used to create transects and statistical analyses for the shoreline. The results show that since 1976 the area of mangrove forests has decreased by 55% and most of it has changed to become fishponds (increased to 35%). The land conversion has resulted in shoreline changes and the biggest erosion occurred in the Pantai Bahagia village with an erosion rate of 15.46 m/year and lost an area of 330,460 Ha.

MORPHOLOGICAL MODELING OF LOW-DUNE BARRIER HEADLAND SYSTEM CHANGES DUE TO HURRICANE FORCING

Coastal barrier landforms serve as the first line of defense against oceanic and meteorological forces. Landward infrastructure and ecosystems, without these barriers, would be significantly more at risk to the flooding and wave forcing caused by extreme storms. Widespread recognition of this function has prompted coastal managers to adopt systematic restoration programs. As an exemplar, the Caminada Headlands (CH) Beach and Dune Restoration Project, located adjacent Port Fourchon, Louisiana (LA), USA cost an estimated $220 million USD and restored ~22.5 kilometers of coastline with a 6.4 million m3 sediment placement. Insight into the performance of the CH restoration during future hurricane impacts requires an understanding of the system’s response to historical storms. In general, the CH experiences high background shoreline erosion rates. Recent historical averages are on the order of 15 m yr-1 [Byres et al., 2017]. This rate may double during active tropical storm seasons, e.g. the year of hurricane Katrina (2005) [Byres et al., 2017] and, at the event time-scale, localized erosion rates spike dramatically as shorelines may translate 100s of meters landward due to dune overwashing and breaching. Calibration of realistic process based morphological models that can accurately simulate these effects require extensive, high fidelity input data. To achieve this end, this study makes use of several monitoring projects in the LA region while employing a coupled XBeach and Delft3D modeling system to simulate the impact of hurricane Gustav (2008) on the CH.

Observations of Wintering Piping Plovers (Charadrius melodus) Positively Associated with Rock Breakwater-Influenced Shorelines in Southwestern Louisiana

ABSTRACT Selman, W. and Collins, S.A., 2018. Observations of wintering piping plovers (Charadrius melodus) positively associated with rock breakwater-influenced shorelines in southwestern Louisiana. Much of the coastline in southwestern Louisiana is undergoing high rates of shoreline erosion, but long-term plans are to armor the majority of this shoreline with offshore rock breakwaters. This area is also considered critical wintering habitat for Piping Plovers (Charadrius melodus). However, to date, little information is available to assess the influence of these shoreline protection measures on Piping Plovers. From 2009 to 2010, three experimental breakwater sections were built along the shoreline of Rockefeller Wildlife Refuge (RWR) in southwestern Louisiana to determine their effectiveness at combating shoreline encroachment. Thereafter, annual Piping Plover surveys were conducted from 2013 to 2017 at RWR along ∼14.5 km of shoreline inclusive of the test sections. Observations included 89 total Piping ...

Impact of Shoreline Changes to Pahang Coastal Area by using Geospatial Technology

Malaysia has a long coastline stretching over 4,809 km where more than 1,300 km of beaches are experiencing erosion. Coastal erosion is recognised as the permanent loss of land and habitats along the shoreline resulting in the changes of the coast. Thus, it is important to detect and monitor shoreline changes especially in Pahang coast by identifying the rate of shoreline erosion and accretion. This study used temporal data and high spatial resolution imagery (SPOT 5) using remote sensing and GIS techniques to monitor shoreline changes along 10 study locations, which is from Cherating to Pekan of the Pahang coast. The total length of shoreline changes is about 14 km (14035.10 m) where all these areas are very likely to experience erosion ranging from 0.1 to 94.7 ha. On the other hand, these coastal areas found a minimal accretion with increased sediment from 0.1 to 2.8 ha. Overall, the coastal areas are exposed to higher erosion process than accretion with a very high vulnerability of erosion rate from 1.8 to 20.9 meter per year. The findings on monitoring shoreline changes and identifying vulnerable erosion areas might be useful in the policy and decision making for sustainable coastal management.

Influence of Shoreline Stabilization Structures on the Nearshore Sedimentary Environment in Mesohaline Chesapeake Bay

Shorelines around many estuaries and coastal embayments are rapidly eroding (approximately several meters/year), with more rapid erosion rates expected in the future due to natural and anthropogenic stressors. In response, a variety of techniques have been used to stabilize shorelines, but there are limited quantitative, long-term data available about their effects on the sedimentary environment immediately adjacent to them (i.e., the nearshore). This study evaluated changes in sediment characteristics (mud and organic content) and accumulation rates associated with installation of breakwaters, riprap, and living shorelines with (“hybrid”) and without (“soft”) a structural component. 210Pb (half-life 22.3 years) geochronologies were used to identify horizons in core profiles that corresponded to years when structures were built. Sites with naturally eroding shorelines (i.e., no structures) were used as a control group at which any sedimentary changes represent broad environmental trends, in contrast to changes at the protected sites that also include the influence of structures. Observations were placed within the context of modeled wave climate, shoreline-erosion rates, land use, dominant sediment source, and the apparent effect on submersed aquatic vegetation (SAV) inhabiting the nearshore sedimentary environment. The main conclusion of this study is that there was no “one size fits all” answer to anticipated impacts of structures on nearshore sedimentary environments. Instead, specific changes associated with structures depended on individual site characteristics, but could be predicted with multiple linear regression models that included structure type, shoreline-erosion rate, dominant sediment source, and land use. Riprap or breakwater installation had either positive or no obvious impact on SAV at six of seven sites but negatively impacted SAV at one riprapped site. No obvious impacts on SAV were observed at living shoreline sites.

Shoreline erosion and decadal sediment accumulation in the Tar-Pamlico estuary, North Carolina, USA: A source-to-sink analysis

Estuaries contain vital habitats and it is important to understand how these areas respond to human activities and natural processes such as sea-level rise and wave attack. As estuarine shorelines erode or become modified with hard structures, there is potential for significantly altering the availability of sediment and the filling of coastal systems. This study used a source-to-sink approach and quantified rates of shoreline erosion in the Tar-Pamlico sub-estuary, a tributary of the larger Albemarle-Pamlico Estuarine System (APES). The average shoreline change rate (SCR) determined using an end-point method was −0.5 ± 0.9 m yr−1 for the Tar-Pamlico. Incorporating bulk density estimates, this contributes 0.6 × 105 tons of fine sediment to the system annually, or after accounting for fluvial input, about 40% of the total sediment supply to the sub-estuary. The role of the Tar-Pamlico as a sink for these sediments was addressed using the radionuclide tracers 210Pb and 137Cs. Radionuclide activities and sediment accumulation rates identified several depositional regions, in particular in the middle of the estuary. Linear sediment accumulation rates ranged from 0.10 ± 0.02 to 0.38 ± 0.02 g cm−2 yr−1, and total storage of fine sediment in the system was 1.6 × 105 t yr−1. It was not possible to confidently discern a change in the rate of shoreline erosion or seabed accumulation. A preliminary budget for fine sediments (grain-size <63 μm) was then calculated to compare erosional sources with sedimentary sinks. Almost all (∼93.0%) of the fine sediment entering the system was accumulated and stored, while only about 7.0% was exported to Pamlico Sound.

Spatial and temporal shoreline changes of the southern Yellow River (Huanghe) Delta in 1976–2016

In this study, 364 Landsat satellite images were utilized to study the spatial and temporal shoreline changes of the southern Yellow River Delta in 1976–2016, and a new method revised and improved after Zhang et al. (2016) was proposed. By employing that method, the calculated sea levels calculated from simulated tidal heights and instantaneous shoreline positions rather than simulated tidal heights were used to correct fluctuations in instantaneous shoreline positions caused by tidal height and seasonal sea level changes and other random sea level fluctuations. When calculating the shoreline erosion rates and beach slopes, a statistical analysis of a large number of corrected shoreline positions was used to reduce the influence of random errors that were mainly caused by waves and other casual factors. The shoreline erosion rates and beach slopes presented in this paper are therefore more precise and reliable than those derived in previous studies, which only used two satellite images.The results of this study show that the shoreline of the southern Yellow River Delta primarily experienced gradual erosion during 1976–2016, with an average erosion rate of 26.9m/year. The average shoreline erosion rate increased from 24.9m/year in 1976–1996 to 34.9m/year in 1996–2016—an increase of 40%—probably due to the reduction in sediment discharge and shifting northward course of the Yellow River after 1996. The shoreline erosion rate of the central coast decreased from 50.2m/year in 1976–1996 to 27.1m/year in 1996–2016—a decrease of 46%—probably due to the protection offered by coastal hard structures. The average shoreline erosion rate caused by relative sea level rise was 8.5m/year or 32% of the total average shoreline erosion rate. Relative sea level rise plays an important role in the erosion of the southern Yellow River Delta due to its flat beach. The beach slope of the southern Yellow River Delta was flat and stable in 1976–2016, and the average slope over most of the beach was 0.043%.

Sedimentation and erosion in Lake Diefenbaker, Canada: solutions for shoreline retreat monitoring.

This study looks into sedimentation and erosion rates in Lake Diefenbaker, a prairie reservoir, in Saskatchewan, Canada, which has been in operation since 1968. First, we looked at the historical data in all different formats over the last 70years, which includes data from more than 20years before the formation of the lake. The field observations indicate high rates of shoreline erosion, especially in the upstream portion as a potential region for shoreline retreat. Because of the great importance of this waterbody to the province, monitoring sedimentation and erosion rates is necessary for maintaining the quality of water especially after severe floods which are more common due to climate change effects. Second, we used Google Maps Elevation API, a new tool from Google that provides elevation data for cross sections drawn between two points, by drawing 24 cross sections in the upstream area extending 250m from each bank. This feature from Google can be used as an easy and fast monitoring tool, is free of charge, and provides excellent control capabilities for monitoring changes in cross-sectional profiles.

Adapting without Retreating: Responses to Shoreline Change on an Inlet-Associated Coastal Beach

ABSTRACTCoastal barrier systems around the world are experiencing higher rates of flooding and shoreline erosion. Property owners on barriers have made significant financial investments in physical protections that shield their nearby properties from these hazards, constituting a type of adaptation to shoreline change. Factors that contribute to adaptation on Plum Island, a developed beach and dune system on the North Shore of Massachusetts, are investigated here. Plum Island experiences patterns of shoreline change that may be representative of many inlet-associated beaches, encompassing an equivocal and dynamically shifting mix of erosion and accretion. In the face of episodic floods and fleeting erosive events, and driven by a combination of strong northeast storms and cycles of erosion and accretion, the value of the average Plum Island residence increases by 34% for properties on the oceanfront where protection comprises a publicly constructed soft structure. Even in the face of state policies that ostensibly discourage physical protection as a means of adaptation, coastal communities face significant political and financial pressures to maintain existing protective structures or to allow contiguous groups of property owners to build new ones through collective action. These factors mitigate against adapting to shoreline change by retreating from the coast, thereby potentially increasing the adverse effects of coastal hazards.

Influences of Wave Climate and Sea Level on Shoreline Erosion Rates in the Maryland Chesapeake Bay

We investigated spatial correlations between wave forcing, sea level fluctuations, and shoreline erosion in the Maryland Chesapeake Bay (CB), in an attempt to identify the most important relationships and their spatial patterns. We implemented the Simulating WAves Nearshore (SWAN) model and a parametric wave model from the USEPA Chesapeake Bay Program (CBP) to simulate wave climate in CB from 1985 to 2005. Calibrated sea level simulations from the CBP hydrodynamic model over the same time period were also acquired. The separate and joint statistics of waves and sea level were investigated for the entire CB. Spatial patterns of sea level during the high wave events most important for erosion were dominated by local north-south winds in the upper Bay and by remote coastal forcing in the lower Bay. We combined wave and sea level data sets with estimates of historical shoreline erosion rates and shoreline characteristics compiled by the State of Maryland at two different spatial resolutions to explore the factors affecting erosion. The results show that wave power is the most significant influence on erosion in the Maryland CB, but that many other local factors are also implicated. Marshy shorelines show a more homogeneous, approximately linear relationship between wave power and erosion rates, whereas bank shorelines are more complex. Marshy shorelines appear to erode faster than bank shorelines, for the same wave power and bank height. A new expression for the rate of shoreline erosion is proposed, building on previous work. The proposed new relationship expresses the mass rate of shoreline erosion as a locally linear function of the difference between applied wave power and a threshold wave power, multiplied by a structure function that depends on the ratio of water depth to bank height.

Evaluation of future land-use planning initiatives to shoreline stability of Egypt’s northern Nile delta

An analysis of beach morphodynamics and relative vulnerability to erosion processes and sea inundation within the Nile delta’s lower coastal plain was performed as a basis for evaluation of future planning initiatives undertaken by the National Centre for Planning State Land Uses (NCPSLU). The conceptual management plans incorporate a variety of land-use plans including residential, recreational, industrial, agricultural, harboring, fish farming, and placer sand mining. Appropriateness of shores fronting the planned land uses is assessed in the present study by applying the Coastal Vulnerability Index (CVI) approach, which depends primarily on a variety of variables that affect beach stability of the proposed plans. These variables are prominent morphologic features, shoreline erosion or accretion rates, sea-level rise, beach type (dissipative, reflective, or rhythmic bar), and oceanographic conditions (tidal range and mean wave height). Results disclosed that not all of the examined delta coastlines are equally vulnerable to beach erosion (ranging from relatively low to highly susceptible). However, the most serious threat is that the relatively stable coastlines lying close to nodal points are likely to be affected by erosion due to net sediment transport reversals heading eastward or westward which eventually may require remedial protection. Future planning of the unprotected highly vulnerable and low-elevated subsiding zones, such as Manzala lagoon barrier, requires effective mitigation measures. Quarrying of Abu Khashaba beach, as an example, for mineral mining placers (at Abu Khashaba) and other fish farming applications (possibly at Burullus lagoon barrier) is considered as a risk and is to be avoided as it accelerates eroding the natural protective barrier that fronts the Burullus lagoon.

Assessment of the susceptibility of the coast of Astypalaea Island (S.E. Aegean Sea) to sea level rise.

The aim of this paper is the classification of the coast of Astypalaea Island (S.E Aegean Sea) according to its susceptibility to an anticipated future sea-level rise, using the Coastal Sensitivity Index (CSI), and utilizing GIS technology. This index allows the following six physical variables: geomorphology, coastal slope, relative sea-level rise rate, shoreline erosion or accretion rate, mean tidal range and mean wave height, to be related in a semi-quantitative manner. Each variable is ranked on the basis of its potential contribution to physical changes on the coast as sea-level rises. Following the CSI calculation, a map is produced for the coastline of the island. This map showed that an extensive length of the coast (121.5 km, corresponding to 84.6% of the island’s coastline) is characterized as very low and low sensitive. Only 12.1 km of the coast, corresponding to 8.5% of the entire coastline, is characterized as very highly and highly sensitive to sea- level rise, primarily due to the low topography and the presence of highly erodible geological formations and landforms. Areas of high and very high CSI values host socioeconomically important land uses and activities as well as environmentally protected areas.

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.

Statistical modeling of interannual shoreline change driven by North Atlantic climate variability spanning 2000–2014 in the Bay of Biscay

Modeling studies addressing daily to interannual coastal evolution typically relate shoreline change with waves, currents and sediment transport through complex processes and feedbacks. For wave-dominated environments, the main driver (waves) is controlled by the regional atmospheric circulation. Here a simple weather regime-driven shoreline model is developed for a 15-year shoreline dataset (2000–2014) collected at Truc Vert beach, Bay of Biscay, SW France. In all, 16 weather regimes (four per season) are considered. The centroids and occurrences are computed using the ERA-40 and ERA-Interim reanalyses, applying k-means and EOF methods to the anomalies of the 500-hPa geopotential height over the North Atlantic Basin. The weather regime-driven shoreline model explains 70% of the observed interannual shoreline variability. The application of a proven wave-driven equilibrium shoreline model to the same period shows that both models have similar skills at the interannual scale. Relation between the weather regimes and the wave climate in the Bay of Biscay is investigated and the primary weather regimes impacting shoreline change are identified. For instance, the winter zonal regime characterized by a strengthening of the pressure gradient between the Iceland low and the Azores high is associated with high-energy wave conditions and is found to drive an increase in the shoreline erosion rate. The study demonstrates the predictability of interannual shoreline change from a limited number of weather regimes, which opens new perspectives for shoreline change modeling and encourages long-term shoreline monitoring programs.

Climate change adaptation in the Schleswig-Holstein sector of the Wadden Sea: an integrated state governmental strategy

Anthropogenic climate change constitutes a main challenge for the Wadden Sea. Accelerated sea level rise, increasing temperatures and changing wind climate may strongly alter present structures and functions of the ecosystem with negative consequences both for nature conservation and for coastal risk management. Being aware of these challenges, Schleswig-Holstein State Government decided to establish an integrated climate change adaptation strategy for the Schleswig-Holstein sector of the Wadden Sea. The strategy was adopted in June 2015. It aims at the long-term maintenance of present functions and structures as well as the integrity of the Wadden Sea ecosystem in a changing climate. The strategy was prepared by a project group consisting of representatives from State authorities as well as from nature conservation organisations and local institutions. First outcome of the strategy is that extra adaptation measures will not be necessary in the coming decades. However, pending on the future rate of sea level rise, shoreline erosion and sediment deficits in the Wadden Sea will increase and sooner or later drowning of tidal flats and terrestrial habitats like beaches, primary dunes and salt marshes will start. At the time when management measures to counteract the negative developments become expedient from a nature conservation viewpoint as well as for coastal risk management, adequate actions with minimized ecological interferences are possible. It is assumed that balancing the sediment deficits as the main adaptation measure may be implemented most efficiently by concentrating sediment suppletion at locations where natural forces organize redistribution in the Wadden Sea. Local technical coastal risk management measures like the strengthening of sea defences will, nevertheless, remain necessary as well.

Shoreline shifting and its prediction using remote sensing and GIS techniques: a case study of Sagar Island, West Bengal (India)

The shoreline position is difficult to predict but the trend of erosion or accretion can be determined by geospatial and statistical techniques which may help in reducing the loss of property. The study aims to assess the shoreline changes and prediction in Sagar Island, a delta of the Ganges, situated in West Bengal, India. Shorelines have been delineated by using Tasseled Cap Transformation techniques from the Landsat MSS (1975), Landsat TM (1989, 1991) and Landsat ETM+ (1999, 2002, 2005, 2008, and 2011) images. The uncertainty was calculated for every year for assessing the positional error related to shoreline extraction. Total shoreline change rate/year has also been calculated and the uncertainty of total shoreline change rate was found ±3.20 m/year. In the present study, End Point Rate (EPR) and Linear Regression (LR) methods have been used for shoreline change rate calculation and prediction of shoreline. Long term (1975–2002) and short term (2002–2011) erosion and accretion rates were calculated for the study area. Sagar is the biggest island of the Sundarban region; so, it was divided into three segments in order to analyze the change on a segment basis. It was observed that the most of erosion occurred in the Segment B (south Sagar). The rate of erosion was −7.91 and −7.01 m/year for the periods 1975–2002 and 2002–2011 respectively. The mean shoreline change rate was high in Segment B (South Sagar) with values of −6.46 m/year (1975–2002) but the rate was decreased into −5.25 m/year during the later period (2002–2011). The study reveals that most of the southern part of Sagar Island is vulnerable to high rate of shoreline erosion.

Carbon export from fringing saltmarsh shoreline erosion overwhelms carbon storage across a critical width threshold

Saltmarshes are carbon storage hotspots and help to offset anthropogenic carbon emissions; however, marshes are threatened by sea-level rise, erosion, and human development. Recent efforts to constrain the saltmarsh carbon cycle have focused on the processes of carbon burial and sequestration with respect to sea-level rise and global warming. Simultaneously, many marshes that fringe the margins of estuaries and barrier islands are eroding, which releases old carbon from the saltmarsh and transports it into the estuary, and that process should be included in marsh carbon budgets. Additionally, if marshes cannot transgress the upland at a rate that balances shoreline retreat, then the marsh will narrow, thus reducing the area available for carbon storage. Here, we present the development of a box model that incorporates both carbon storage and carbon export via shoreline erosion to estimate the annual carbon budget of saltmarsh sediments. We test the model using field data collected at a fringing marsh within the Rachel Carson National Estuarine Research Reserve in North Carolina. The shoreline erosion rates along the fringing marsh are variable and the model output shows that the stretch of marsh that is retreating 0.76 m yr−1 switched to a carbon source in 1930, while another portion of the marsh that is retreating more slowly (0.65 m yr−1) will switch to a source in 2021. The model indicates that the carbon budget of a saltmarsh is highly sensitive to the rate of shoreline retreat and that rapidly-eroding marshes may already be net sources of carbon. These results underscore the importance of conserving existing marshes, mitigating shoreline erosion, and considering shoreline erosion in the design of saltmarsh restoration projects.