Shoreline Segments Research Articles

An Improved One-Line Evolution Formulation for the Dynamic Shoreline Planforms of Embayed Beaches

In this paper, an improved one-line evolution formulation is proposed and derived for the dynamic shoreline planforms of embayed beaches. Although embayed sandy beaches can perform several functions, serving as leisure spots and areas of coastal protection, shoreline advances and retreats occur continuously as a result of many natural forces, such as winds, waves, currents, tides, etc. The one-line evolution formulation for dynamic shoreline planforms based on the polar coordinate can be adopted to simulate high-planform-curvature shorelines and achieve better stability and simplicity in comparison with other description coordinates. While the polar coordinate and rectangular control volume are adopted to derive the one-line evolution formulation for dynamic shoreline planforms, the difference between the radial direction of the polar coordinate and the normal direction of the shoreline segment may result in inaccurate predictions of shoreline movements. In this study, a correction coefficient, which can adjust the influence of these two misaligned directions, is derived and included in the one-line evolution formulation, which is based on the polar coordinate. Thus, by considering the correction coefficient, an improved one-line evolution formulation for dynamic shoreline planforms of crenulate-shaped bays is proposed in this paper. Some numerical examples are provided to verify the merits of the proposed improved one-line evolution formulation. Moreover, the proposed numerical approach is applied to simulate the dynamic movements of the shoreline in Taitung—the southeastern part of Taiwan—and the effectiveness of the proposed formulation in solving realistic engineering applications is evidently verified.

Using vulnerability assessment to characterize coastal protection benefits provided by estuarine habitats of a dynamic intracoastal waterway.

The existence of coastal ecosystems depends on their ability to gain sediment and keep pace with sea level rise. Similar to other coastal areas, Northeast Florida (United States) is experiencing rapid population growth, climate change, and shifting wetland communities. Rising seas and more severe storms, coupled with the intensification of human activities, can modify the biophysical environment, thereby increasing coastal exposure to storm-induced erosion and inundation. Using the Guana Tolomato Matanzas National Estuarine Research Reserve as a case study, we analyzed the distribution of coastal protection services-expressly, wave attenuation and sediment control-provided by estuarine habitats inside a dynamic Intracoastal waterway. We explored six coastal variables that contribute to coastal flooding and erosion-(a) relief, (b) geomorphology, (c) estuarine habitats, (d) wind exposure, (e) boat wake energy, and (f) storm surge potential-to assess physical exposure to coastal hazards. The highest levels of coastal exposure were found in the north and south sections of the Reserve (9% and 14%, respectively) compared to only 4% in the central, with exposure in the south driven by low wetland elevation, high surge potential, and shorelines composed of less stable sandy and muddy substrate. The most vulnerable areas of the central Reserve and main channel of the Intracoastal waterway were exposed to boat wakes from larger vessels frequently traveling at medium speeds (10-20 knots) and had shoreline segments oriented towards the prevailing winds (north-northeast). To guide management for the recently expanded Reserve into vulnerable areas near the City of Saint Augustine, we evaluated six sites of concern where the current distribution of estuarine habitats (mangroves, salt marshes, and oyster beds) likely play the greatest role in natural protection. Spatially explicit outputs also identified potential elevation maintenance strategies such as living shorelines, landform modification, and mangrove establishment for providing coastal risk-reduction and other ecosystem-service co-benefits. Salt marshes and mangroves in two sites of the central section (N-312 and S-312) were found to protect more than a one-quarter of their cross-shore length (27% and 73%, respectively) from transitioning to the highest exposure category. Proposed interventions for mangrove establishment and living shorelines could help maintain elevation in these sites of concern. This work sets the stage for additional research, education, and outreach about where mangroves, salt marshes, and oyster beds are most likely to reduce risk to wetland communities in the region.

Coastline Monitoring and Prediction Based on Long-Term Remote Sensing Data—A Case Study of the Eastern Coast of Laizhou Bay, China

Monitoring shoreline movements is essential for understanding the impact of anthropogenic activities and climate change on the coastal zone dynamics. The use of remote sensing allows for large-scale spatial and temporal studies to better comprehend current trends. This study used Landsat 5 (TM), Landsat 8 (OLI), and Sentinel-2 (MSI) remote sensing images, together with the Otsu algorithm, marching squares algorithm, and tidal correction algorithm, to extract and correct the coastline positions of the east coast of Laizhou Bay in China from 1984 to 2022. The results indicate that 89.63% of the extracted shoreline segments have an error less than 30 m compared to the manually drawn coastline. The total length of the coastline increased from 166.90 km to 364.20 km, throughout the observation period, with a length change intensity (LCI) of 3.11% due to the development of coastal protection and engineering structures for human activities. The anthropization led to a decrease in the natural coastline from 83.33% to 13.89% and a continuous increase in the diversity and human use of the coastline. In particular, the index of coastline diversity (ICTD) and the index of coastline utilization degree (ICUD) increased from 0.39 to 0.79, and from 153.30 to 390.37, respectively. Over 70% of the sandy beaches experienced erosional processes. The shoreline erosion calculated using the end point rate (EPR) and the linear regression rate (LRR) is 79.54% and 85.58%, respectively. The fractal dimension of the coastline shows an increasing trend and is positively correlated with human activities. Coastline changes are primarily attributed to interventions such as land reclamation, aquaculture development, and port construction resulting in the creation of 10,000.20 hectares of new coastal areas. Finally, the use of Kalman filtering for the first time made it possible to predict that approximately 84.58% of the sandy coastline will be eroded to varying degrees by 2032. The research results can provide valuable reference for the scientific planning and rational utilization of resources on the eastern coast of Laizhou Bay.

Shoreline Dynamics in the Very Small Islands of Karimunjawa – Indonesia: A Preliminary Study

Indonesia is considered one of the biggest archipelagic countries in the world. According to some literature, Indonesia has more than 17,000 islands, most of which are classified as small islands. Some of these islands have become important areas for tourism, for instance, small islands in Karimunjawa. However, some of these islands experienced shoreline changes caused by erosion and accretion. Hence, this research aims to map the spatial distribution of shoreline change using the Digital Shoreline Analysis System (DSAS) add-in on ArcGIS. The primary dataset utilized as input consists of Sentinel 2A imagery captured over 2017 and 2022. The results showed that around 89 segments, or 51.47% of the total shoreline segments, tend to experience accretion, while the remaining 79 segments, or 45.93%, experience erosion. This finding suggests that most shoreline segments tend to accrete or seaward movement in the research area. The results of this study exhibit notable disparities when compared to the occurrences observed in Pandeglang (Banten), Kuwaru (Yogyakarta), Buleleng (Bali), and East Java Province, where coastal erosion prevails over accretion. The managers of the islands try to reduce the threat of erosion by constructing dykes and breakwaters. However, these buildings are ineffective due to the relatively simple structures and building materials. Therefore, further studies are needed to determine the type and specification of mitigation buildings that are suitable for implementation in that location.

Subrecent charophyte flora from the Pheneos palaeolake (Greece): Palaeoecological implications

Herein, the late Quaternary charophyte flora from the Pheneos palaeolake in north Peloponnese (Greece) is examined for the first time. The Pheneos palaeolake was located in the south region of the Pheneos polje, where late Quaternary relict shoreline segments are still preserved. These shorelines correspond to the fluctuation of the water level at different periods reflecting the polje’s successive flooding and draining. Sediment sampling was conducted at 4 levels representing ancient shorelines of the lake. Up to five charophyte taxa have been identified and illustrated based on parautochtonous oospores and gyrogonites i.e., Nitella cf. hyalina, Sphaerochara prolifera, Chara vulgaris, Chara sp. and Nitellopsis obtusa. The distribution of the flora within the four studied levels allows the distinction of three different palaeoenvironmental conditions that prevailed at the paleolake´s margins during the late Quaternary. The occurrence of S. prolifera in the lowest elevation level indicates the prevalence of ephemeral annual flooding conditions of the lake´s margin. N. obtusa has been recovered from both the lowest and the upper lowest levels reflecting permanent, oligohaline, oligotrophic, and cold-water conditions. Chara vulgaris and Chara sp. are present in the uppermost two levels reflecting less permanent and oligotrophic conditions. The distribution of the charophyte flora in the Pheneos palaeolake suggests major changes in the palaeoecological conditions of the lake ranging from permanent, cold and oligotrophic to ephemeral and more eutrophic.

A Quantitative Comparison of Oil Sources on Shorelines of Prince William Sound, Alaska, 17 Years After the Exxon Valdez Oil Spill.

Environmental damage caused by accidental discharges of pollutants depends in part on the degree of prior contamination, in that increased pollution of an already heavily contaminated region will usually be considered less detrimental than equivalent pollution of a pristine region. Quantitative comparisons of specific pollution events with the extent and severity of prior contamination are rare, owing to difficulties in identifying and assessing contaminants remaining from prior pollution events, and in some cases contaminants from natural sources. The 1989 Exxon Valdez oil spill (EVOS) presents an unusual opportunity to quantitatively evaluate residual contaminants from petroleum sources on shorelines of Prince William Sound (PWS), Alaska. Here, we evaluate surface oil contamination from Monterey Formation petroleum-derived residues (released into PWS from ruptured storage tanks during the 1964 earthquake) on 200 shoreline segments selected at random within the EVOS spill path. We compare these results with previously estimated contamination from the EVOS and from other human activities. Our results indicate that residual shoreline contamination from the EVOS is more than ~ 50% greater than the sum total from human activity sites, that residual contamination by Monterey Formation sources is negligible in comparison to that from the EVOS, and that most of the shorelines in PWS were as close to pristine prior to the EVOS as is likely to be found anywhere else worldwide.

Creating adaptive social-ecological fit: The role of regional actors in the governance of Sea-level rise adaptation in San Francisco bay

Sea level rise is one of the most pressing climate adaptation issues around the world. Often, coastal communities are interdependent in their exposure to sea level rise – if one builds a seawall, it will push water to another – and would benefit from a coordinated adaptive response. The literature on social-ecological systems (SES) calls for actors placed at higher levels of governance (e.g. regional government in a metropolitan area) to improve coordination between local managers by serving as brokers. However, we lack empirical insight on how higher-level actors might improve coordination in practice, and theoretical development on the implications of their intermediation. To address these gaps, we study the case of adaptation to sea level rise in the San Francisco Bay Area. We build a social-ecological network of social actors and shoreline segments using original survey data and simulated scenarios of tidal and traffic interdependencies between shoreline segments. We perform a frequency analysis of network motifs that operationalize social-ecological ‘fit’ in the context of the Bay Area. We find that regional actors and non-governmental organizations increase social-ecological fit by providing intermediation between actors who work on different shoreline segments, whether interdependent or not. This shows that these actors provide adaptive social-ecological fit, future-proofing the Bay Area to current and future climate adaptation challenges.

Sea level rise vulnerability assessment for State wildlife areas surrounding Humboldt Bay, northern California

Humboldt Bay has the highest rate of sea level rise (SLR) in California (47.2 cm/century). Due to compaction and tectonic subsidence, former tidelands and pastures behind dikes surrounding Humboldt Bay are lower in elevation than bay waters at high tide. Adaptation to future climate change and SLR requires that resource managers understand vulnerability and risk to each wildlife area at a local level, because adaptation to SLR is a risk-based management strategy against an uncertain future requiring site-specific solutions. We conducted a vulnerability assessment of the shoreline of three State wildlife areas surrounding Humboldt Bay: Elk River (ERWA), Fay Slough (FSWA), and Mad River Slough (MRSWA). Breaching of shorelines that border each refuge has the potential to flood a diversity of wetland communities, wildlife habitats, and critical infrastructure within the historic tidal inundation footprint. The total length of diked 1-m shoreline segments potentially impacted by SLR was 6.2 km. The relationship between vulnerability and elevation of diked shoreline segments was significantly correlated for all wildlife areas. Vulnerability of diked shoreline was significantly affected by the type of surface covering. MRSWA had the highest percentage of shoreline fortified with concrete and rock (62.2% [2,876 m]), followed by ERWA (0.3% [2,815 m]). ERWA and FSWA had the greatest percentage of shoreline anchored by vegetation (99.3% [2,834 m] and 91.5% [3,385 m], respectively); FSWA had the highest percentage of unvegetated (i.e., exposed) shoreline (7.4% [252 m]); and ERWA had the highest percentage (86.6% [436 m]) of diked shoreline followed by FSWA (69.2% [633 m]) and MRSWA (33.0% [276 m]). The highest overall ratings of shoreline vulnerability were at ERWA (91.7%), followed by FSSWA (72,4%), and MRSWA (34.4%). Issues related to retention of unique characteristics of each wildlife area, natural resources and species at risk, and adaptive planning for future SLR are discussed.

Ship wake forcing and performance of a living shoreline segment on an estuarine shoreline

Investigation of the effectiveness of Natural and Nature-Based Features (NNBF) for protecting shorelines from ship wake is increasingly important with continued development along the coast, especially when combined with sea level rise. Studies that investigate the wave energy dissipation capacity of different techniques and account for variation in context will lead to improvements and innovation in designed NNBF. Few studies have examined the performance of NNBF in protecting shorelines from ship wake. In this study of a low-sloping estuarine shoreline adjacent to a major shipping route, a natural design using coir logs and wooden staking was implemented in a T-head groin configuration. Pressure transducers and electromagnetic current meters were deployed over ∼1.5 months to investigate the energy dissipation and velocity attenuation capabilities of the installation. Results indicate that ship wakes account for 25%–50% of the total daily energy impacting the shoreline at the study site. Peak background velocities are typically over 50% smaller than the largest ship wake velocities. Field data and results of the fully nonlinear Boussinesq model, FUNWAVE-TVD, indicate that the installation is capable of decreasing energy impacting the shoreline by 10%–80% and is effective over the lower 50% of the tidal range and when submerged up to twice its height. Elevation surveys of the site indicate accrual of sediment within the installation, suggesting wave diffraction patterns promoting further accretion at the site over time. Observations indicate that coir logs may be effective in reducing wave energy from ship wakes but may fail under storm conditions in a moderate fetch confined channel. Findings from this study illustrate the opportunities and challenges nature-based solutions face in addressing ship wakes, and their ability to protect shorelines under high energy stressors.

Economic evaluation of sea-level rise adaptation strongly influenced by hydrodynamic feedbacks

Coastal communities rely on levees and seawalls as critical protection against sea-level rise; in the United States alone, $300 billion in shoreline armoring costs are forecast by 2100. However, despite the local flood risk reduction benefits, these structures can exacerbate flooding and associated damages along other parts of the shoreline-particularly in coastal bays and estuaries, where nearly 500 million people globally are at risk from sea-level rise. The magnitude and spatial distribution of the economic impact of this dynamic, however, are poorly understood. Here we combine hydrodynamic and economic models to assess the extent of both local and regional flooding and damages expected from a range of shoreline protection and sea-level rise scenarios in San Francisco Bay, California. We find that protection of individual shoreline segments (5 to 75 km) can increase flooding in other areas by as much as 36 million m3 and damages by $723 million for a single flood event and in some cases can even cause regional flood damages that exceed the local damages prevented from protection. We also demonstrate that strategic flooding of certain shoreline segments, such as those with gradually sloping baylands and space for water storage, can help alleviate flooding and damages along other stretches of the coastline. By matching the scale of the economic assessment to the scale of the threat, we reveal the previously uncounted costs associated with uncoordinated adaptation actions and demonstrate that a regional planning perspective is essential for reducing shared risk and wisely spending adaptation resources in coastal bays.

Shoreline Change Analysis of Pontang Cape of Serang Regency of Banten Province

Coastal areas, being vulnerable to environmental problems, have one of the most frequent problems which are the change in the shorelines. Shoreline changes, namely abrasions, can cause problems such as land degradations or loss of land in a coastal zone. This problem occurs in many areas, one of which is Pontang Cape. This study aims to determine the distance and rate of shoreline changes that occured in the Cape and its surroundings, as well as explaining the analysis points based on similar studies that had been conducted. This research used ArcMap software and Digital Shoreline Analysis System (DSAS) toolset to determine the distance and rate of shoreline changes for 19 years (1999-2018). Based on the results, there were two shoreline segments where different phenomena of shoreline change took place, namely Banten Bay (accretion) and Pontang Cape-Lontar (abrasion). The most likely causes of changes in the shorelines are sediment runoffs from rivers that lead to bay and sediment transports that affect Banten Bay accretions, while sea sand mining and conversions of mangrove swamps into fishery ponds are factors affecting abrasions in Pontang Cape.Keywords: Abrasion, Accretion, Pontang Cape, Banten Bay, DSAS

Risk of shoreline hardening and associated beach loss peaks before mid-century: O\u02bbahu, Hawai\u02bbi

Shoreline hardening, which causes beach loss globally, will accelerate with sea level rise (SLR), causing more beach loss if management practices are not changed. To improve beach conservation efforts, current and future shoreline hardening patterns on sandy beaches need deeper analysis. A shoreline change model driven by incremental SLR (0.25, 0.46, 0.74 m) is used to simulate future changes in the position of an administrative hazard zone, as a proxy for risk of hardening at all sandy beaches on the island of O‘ahu, Hawai ‘i. In Hawai ‘i, hardening can be triggered when evidence of erosion is within 6.1 m (“20 ft”) of certain structures, allowing an applicant to request emergency protection. Results show an increase in shoreline vulnerability to hardening with SLR governed by backshore land use patterns. The largest increase (+ 7.6%) occurred between modern-day and 0.25 m of SLR (very likely by year 2050) with half of all beachfront shoreline at risk by 0.74 m of SLR. Maximum risk of shoreline hardening and beach loss is projected to occur from modern-day and near-term hardening because of the heavily developed aspect of some shoreline segments. Adaptation to SLR should be considered an immediate need—not solely a future issue.

Maximizing surveillance through spatial characterization of marine mammal stranding hot spots

AbstractSpatial analyses of marine mammal stranding data can be used to identify stranding patterns and improve surveillance and monitoring. Using ArcGIS and SaTScan, we analyzed 12 years (2002–2014) of dead beachcast marine mammals from San Juan County, Washington, to better understand patterns of carcass deposition. We plotted the locations for 631 dead marine mammals and aggregated strandings into 1,000 m segments of shoreline. “Hot spots” included beach segments with significantly higher carcass deposition according to the Getis‐Ord Gi* statistic in ArcGIS or beach segments that were encompassed by significant spatial clusters using the discrete Poisson model in SatTScan. We identified 52 hot spots for harbor seals (Phoca vitulina) in ArcGIS and 62 hot spots in SaTScan with 81% agreement between methods. Carcass deposition showed a strong relationship with locations having high proximity to public pedestrian access points, suggesting increased reporting effort in those areas. Stranding frequency was also higher on beach segments with longer fetch and nearly level or gentle slopes. Beaches with these geomorphic characteristics, especially those without high proximity to public access, would be ideal locations to actively survey to improve high quality carcass collection during times of high expected mortality and limited resources.

Calculating Rates of Shoreline Change in a Coastal Embayment with Fringing Salt Marsh Using the “Marshline”, a Proxy-Based Shoreline Indicator

Along the shoreline of a coastal lagoon with fringing salt marsh, we used the basinward edge of marsh vegetation, or marshline, as a shoreline indicator. We quantified uncertainties associated with the delineation of this indicator from aerial photographs. Where both could be delineated, we compared the marshline to the most widely used proxy-based shoreline indicator, the high water line (HWL). The marshline was shown to better represent change than the HWL along fringing marsh shorelines in this study. The visual cues used to delineate the marshline on aerial photographs were more objective, repeatable, and reliable than the visual cues associated with the HWL. In addition, several sources of uncertainty in calculating rates of shoreline change are eliminated, or significantly reduced, when using the marshline. Uncertainties associated with the timing of aerial photographs regarding tidal stage, seasonality, storm impact, as well as the misinterpretation of the shoreline indicator are all either negligible or of minimal influence when calculating uncertainty for the marshline. We calculated rates of shoreline change along a 40-km stretch of lagoon shoreline with fringing marsh. Less than 9.8 km of coast was outside the range of uncertainty using the HWL as compared to 22.5 km using the marshline for the same segments of shoreline for the same temporal period.

Evaluation of storms through the lens of erosion potential along the New Jersey, USA coast

Coastal erosion is driven by both a storm's erosion potential and by an area's vulnerability. Therefore, the problem of estimating impacts can be approached in two-step. The first includes an assessment of erosion potential based on readily available storm parameters, while the second combines this information with highly localized parameters, describing vulnerability, to more directly predict local impacts. The work presented in this paper focuses on this first step, where a storm erosion potential climatology is developed by analyzing historical storms and is then utilized to identify historic patterns. Specifically, storms which have impacted the New Jersey coast over the past several decades are reevaluated using the Storm Erosion Index (SEI), developed by Miller and Livermont (2008), which considers the three primary storm-related drivers of coastal erosion (wave height, water level, and storm duration). These storms are assessed at thirteen shoreline segments defined along New Jersey's Atlantic coast from a 34 year-period (1980–2013) when concurrent wave and water level data is available. Approximately 130 unique storms are identified with the top three being the December 1992 nor'easter, the November 2009 Veteran's Day Storm, and Hurricane Sandy in October 2012, each having an estimated return period of greater than 15 years. The resulting climatology is found to exhibit several interesting spatial and temporal trends. Both portions of the state as well as months of the year that have historically experienced more storms and/or higher cumulative SEI (over the 34 years) are identified. While analysis of the climatology has also identified periods of reduced storm activity and those of intensified conditions, future monitoring is suggested to assess whether these patterns are persistent or related to climatic variations with cycles longer than can be captured by the thirty years included in this study.

The ecosystem service of property protection and exposure to environmental stressors in the Gulf of Mexico

Environmental stressors such as sea-level rise, erosion, and increased storm frequency and intensity are exposing coastal properties to greater amounts of damage. Coastal habitats like beaches, dunes, seagrasses, and wetlands can help reduce exposure and property damage. Using InVEST's Coastal Vulnerability Model, an exposure index value was calculated for every 250 m2 segment along the coastline in Escambia and Santa Rosa counties in Florida, USA. Nineteen sea level-by-habitat management scenarios were evaluated for a suite of shoreline segments across multiple exposures that can be used to inform local decision making as part of larger strategies for coastal management. Overall, a rise in sea level and degradation of coastal habitats could decrease the number of lower exposed shoreline segments and increase the number of higher exposed shoreline segments. These results were used to identify changes in the amount of potential residential property damage among different scenarios. Under high sea levels, additional protection to coastal habitats could reduce the amount of residential property damage resulting from one tropical cyclone event by $50.4 million (2018 US dollars (USD)) (by the year 2050) and by $71.8 million (2018 USD) (by the year 2100) in Escambia and Santa Rosa counties. This research demonstrates the effects that habitat type/abundance and sea-level rise could have on vulnerable coastlines. The results of the modeled scenarios can be incorporated into several recent community resiliency planning initiatives in the region to develop more robust management plans and preparations for a changing environment.

An Effective Low-Cost Remote Sensing Approach to Reconstruct the Long-Term and Dense Time Series of Area and Storage Variations for Large Lakes.

Inland lakes are essential components of hydrological and biogeochemical water cycles, as well as indispensable water resources for human beings. To derive the long-term and continuous trajectory of lake inundation area changes is increasingly significant. Since it helps to understand how they function in the global water cycle and how they are impacted by climate change and human activities. Employing optical satellite images, as an important means of lake mapping, has been widely used in the monitoring of lakes. It is well known that one of the obvious difficulties of traditional remote sensing-based mapping methods lies in the tremendous labor and computing costs for delineating the large lakes (e.g., Caspian Sea). In this study, a novel approach of reconstructing long-term and high-frequency time series of inundation areas of large lakes is proposed. The general idea of this method is to obtain the lake inundation area at any specific observation date by referring to the mapping relationship of the water occurrence frequency (WOF) of the selected shoreline segment at relatively slight terrains and lake areas based on the pre-established lookup table. The lookup table to map the links of the WOF and lake areas is derived from the Joint Research Centre (JRC)Global Surface Water (GSW) dataset accessed in Google Earth Engine (GEE). We select five large lakes worldwide to reconstruct their long time series (1984–2018) of inundation areas using this method. The time series of lake volume variation are analyzed, and the qualitative investigations of these lake changes are eventually discussed by referring to previous studies. The results based on the case of North Aral Sea show that the mean relative error between estimated area and actually mapped value is about 0.85%. The mean R2 of all the five lakes is 0.746, which indicates that the proposed method can produce the robust estimates of area time series for these large lakes. This research sheds new light on mapping large lakes at considerably deducted time and labor costs, and be effectively applicable in other large lakes in regional and global scales.

Spatial Bayesian Network for predicting sea level rise induced coastal erosion in a small Pacific Island

An integrated approach combining Bayesian Network with GIS was developed for making a probabilistic prediction of sea level rise induced coastal erosion and assessing the implications of adaptation measures. The Bayesian Network integrates extensive qualitative and quantitative information into a single probabilistic model while GIS explicitly deals with spatial data for inputting, storing, analysing and mapping. The integration of the Bayesian Network with GIS using a cell-by-cell comparison technique (aka map algebra) provides a new tool to perform the probabilistic spatial analysis. The spatial Bayesian Network was utilised for predicting coastal erosion scenarios at the case study location of Tanna Island, Vanuatu in the South Pacific. Based on the Bayesian Network model, a rate of the island shoreline change was predicted probabilistically for each shoreline segment, which was transferred into GIS for visualisation purposes. The spatial distribution of shoreline change prediction results for various sea level rise scenarios was mapped. The outcomes of this work support risk-based adaptation planning and will be further developed to enable the incorporation of high resolution coastal process models, thereby supporting localised land use planning decisions.

DEVELOPMENT OF A STORM EROSION CLIMATOLOGY FOR THE NEW JERSEY COAST, US

In this study, the Storm Erosion Index (SEI), developed by Miller and Livermont (2008), is used to reevaluate storms that have impacted New Jersey over the past several decades based on their erosion potential. This index considers all three drivers of coastal erosion including wave height, water level, and storm duration and has been shown to more closely correlated to observed erosion than more traditional indices (Miller and Livermont 2008). Here, storms are assessed at thirteen shoreline segments defined along the Atlantic coast of New Jersey. When reevaluated with SEI, the top three storms across all shoreline segments are the December 1992 nor’easter, the Veteran’s Day Storm in November 2009, and Hurricane Sandy in October 2012. In general, the December 1992 nor’easter and Hurricane Sandy are more highly ranked in the northern half of the state with Hurricane Sandy having a maximum return period of 38 years. The Veteran’s Day Storm on the other hand is more highly ranked in the southern half of the state having a maximum return period of 42 years. A closer look at these three storms illustrates the importance of each of the three drivers of coastal erosion in determining erosion potential. A particular emphasis is placed on storm duration which explains why the Veteran’s Day Storm (td = ~90 hours) outranks Hurricane Sandy (td = ~60 hours) in the southern portion of the state. The assessment performed in this study produces a record of historical storms ranked by SEI that future storms can be compared to. This allows for an understanding of the erosion potential of future storms in the context of what has occurred previously.

Mapping Shoreline Variability of Two Barrier Island Segments Along the Florida Coast

Recent projections of global climate change necessitate improved methodologies that quantify shoreline variability. Updated analyses of shoreline movement provide important information that can aid and inform likely intervention policies. This paper uses the Analyzing Moving Boundaries Using R (AMBUR) technique to evaluate shoreline change trends over the time period 1856 to 2015. Special emphasis was placed on recent rates of change, during the 1994 to 2015 period of active storm conditions. Small segments, on the order of tens of kilometers, along two sandy barrier island regions on Florida’s Gulf and Atlantic coasts were chosen for this study. The overall average rate of change over the 159-year period along Little St. George Island was − 0.62 ± 0.12 m/year, with approximately 65% of shoreline segments eroding and 35% advancing. During periods of storm clustering (1994–2015), retreat rates along portions of this Gulf coast barrier accelerated to − 5.49 ± 1.4 m/year. Along the northern portion of Merritt Island on Florida’s Atlantic coast, the overall mean rate of change was 0.22 ± 0.08 m/year, indicative of a shoreline in a state of relative dynamic equilibrium. In direct contrast with the Gulf coast shoreline segment, the majority of transects (65%) evaluated along the oceanfront of Merritt Island over the long term displayed a seaward advance. Results indicate that episodes of clustered storm activity with fairly quick return intervals generally produce dramatic morphological alteration of the coast and can delay natural beach recovery. Additionally, the data show that tidal inlet dynamics, shoreline orientation, along with engineering projects, act over a variety of spatial and temporal scales to influence shoreline evolution. Further, the trends of shoreline movement observed in this study indicate that nearshore bathymetry—the presence of shoals—wields some influence on the behavior of local segments of the shoreline.