Average Shoreline Research Articles

Assessment of shoreline dynamics and vulnerability along the Central Kerala Coast using a geospatial approach

Coastal areas are susceptible to coastal processes, such as sea level rise and natural disasters, making them highly dynamic and vulnerable. The study examines factors such as shoreline changes, coastal slope, wave height, tidal range and landforms and shows distinct erosion, accretion and stability patterns across six littoral cells. Coastal slope and sea level rise are crucial for vulnerability assessment, with low slopes and rising sea levels indicating areas of higher risk. The Coastal Vulnerability Index categorizes zones as low, medium and high risk based on physical variables, while the linear regression method calculates an average shoreline change of −2.41 m/year erosion and 2.59 m/year accretion from 1990 to 2015. The results show that 68.14% of the shoreline is classified as low risk, 17.82% as stable and 14.18% as high risk.

Tidal Flat Erosion Processes and Their Dynamic Mechanisms on the South Side of Sheyang River Estuary, Jiangsu Province

Tidal flats are accumulations of fine-grained sediment formed under the action of tides and play a very important role in coastal protection. The northern part of Jiangsu coast, as a typical example of muddy coasts found all over the world, has experienced serious erosion since the Yellow River shifted northward, and the range of erosion has been gradually extending southward, now reaching the south of the Sheyang River estuary (SYRE). In order to address coastal erosion near the SYRE through protective measures, there is an urgent need for research on the spatial and temporal variation of coastal erosion processes and their control mechanisms in the SYRE and adjacent coastal areas. For this study, the tidal flats on the south side of the SYRE were selected as the study area, and the sediment dynamics in the upper and lower intertidal flat were observed in different seasons to investigate the erosion processes and their dynamic mechanisms. The results show that the tidal current and wave action in the observed intertidal flats are stronger in winter than in summer, and these intertidal flats erode under the combined action of waves and currents. During winter, the net transport of the near-bottom suspended sediment and bedload is primarily towards the southeast, while in summer, the direction tends toward the north and northeast. The net transport fluxes are larger in the lower part of the intertidal flat than in the upper part in summer and also larger in winter than in summer within the lower intertidal flat. Furthermore, the tidal flat erosion in the study area manifests as shoreline retreat and flat surface erosion. The average shoreline retreat rate increased from 23.3 m/a during 2014–2019 to 43.5 m/a during 2019–2021, and the average erosion depth of the lower and upper parts of the intertidal flat over a tidal cycle is, respectively, 1.98 cm and 0.24 cm in winter and 1.65 cm and 0.26 cm in summer. The ratio of the wave-induced bottom shear stress to the tidal current-induced bottom shear stress is 0.40~0.46 in the lower intertidal flat and increases to 0.66~0.67 in the upper intertidal flat, indicating that the intertidal flat erosion in the study area is primarily driven by tidal currents, with significant contributions from wave action, especially in the upper intertidal flat.

Geospatial analysis of shoreline and areal dynamics in the Ganges deltaic island of Bangladesh using the GIS-DSAS technique

Manpura Island, located at the mouth of the Ganges-Brahmaputra-Meghna (GBM) River estuary, is a well-known Ganges deltaic island prone to severe erosion. This study aims to identify shoreline and areal changes in Manpura Island of Bangladesh from 1990 to 2020 using the digital shoreline analysis system (DSAS), a plugin of ArcGIS. The estimation of shoreline variability was primarily described for four segments of the Island: Segment A in the north, Segment B in the west, Segment C in the south, and segment D in the east. It was observed that all four segments of the study area are vulnerable to high rates of shoreline erosion. Landward movement was high in Segment A where Net Shoreline Movement (NSM) was −4000.1 m. Landward movement was also high in Segments B and C with the NSM of −1084.7 m and −1021.6 m, respectively. According to the End Point Rate (EPR) and Linear Regression Rate (LRR), Segment A exhibited a very dynamic feature, with an average shoreline change rate of −24.7 m/yr and −24.2 m/yr, respectively. In Segment C, the average shoreline change rate was −8.5 m/yr for EPR and −9.1 m/yr for LRR. Approximately 392 transects were constructed in the four segments of the island, with approximately 330–334 showing landward movement and 58–62 showing seaward movement. Nevertheless, the island lost about 28.4 km2 in land area and gained only around 2.3 km2 of its original landmass during the study period. The total loss of shoreline length was about 11.5 km (0.4 km/yr), while the total loss of land area was about 26.1 km2 (0.9 km2/yr). The main factors of shoreline change in the study region is likely to be high river discharge, stormy climate and, human interference. The results of this study are useful for the proper management and planning of Manpura Island. However, they can also be used in statistical approaches to forecasting possible shoreline locations in the future under double pressure of climate change and human activities.

Long term investigation on shoreline changes of an Island, inside a Gulf (Hormuz Island)

Shorelines, as the boundary between the body of water and the land, are influenced by different natural and anthropogenic factors. As a consequence, they are highly dynamic and are of great concern for coastal zone management. However, their behavior varies depending on their location, whether they are situated in the open ocean or within a semi-enclosed body of water. Besides, anthropogenic activities in developed beaches and/or coastal cities are the main reason for high rates of change. Thus, normally pristine and undeveloped areas are likely to experience lower rate of shoreline transformation. Hormuz Island as a typical undeveloped pristine island, with minimum anthropogenic activities in its coastlines, located inside a semi-enclosed body of water of the Persian Gulf, is the case study for this research. The alteration of the shoreline is extensively studied for 30 years. The shoreline change is analyzed using net shoreline movement, and linear regression rate indexes of the digital shoreline analysis system tool. Our findings indicated that alterations in the shoreline of Hormuz Island primarily align with natural processes, and the impact of anthropogenic activities on these changes is constrained. The average shoreline change is approximately 0.1 m/year and seldom surpasses 2.0 m/year. These outcomes align with findings observed in other undisturbed regions situated within semi-enclosed bodies of water, such as gulfs or bays. Utilizing identified shoreline alterations, our study area was categorized into three classes: dominant accretion, dominant erosion, and negligible transformation. The shore with negligible changes encompasses more than half of the island. Acknowledging the restricted variability in alterations observed in the beaches within the semi-enclosed area, there is a recognized need to develop an international classification for these types of beaches, in order to be comparable with each other all around the world.

Satellite observations of storm erosion and recovery of the Ebro Delta coastline, NE Spain

Storms and extremely energetic events may significantly impact the form and structure of beaches, and so cause erosive processes and coastal damages. Efficient management actions require an up-to-date and accurate knowledge of beach morphological changes, with the shoreline position being a good indicator of such changes. This work proposes the use of the open-source Shoreline Analysis and Extraction Tool (SAET) software for the definition of satellite-derived shorelines (SDSs) from L8 and Sentinel-2 imagery to reveal the shoreline position changes at the beaches of the Ebro Delta, NE Spain. Spatial-temporal models (STMs) of shoreline changes enable a characterisation of how the beaches responded to the storms of 2020. In conjunction with wave data, STMs enable an analysis of the erosive response to storm events, as well as a monitoring of subsequent beach recovery in the short and medium term (<1 year). Results show how Storm Gloria (January 2020, Hs max = 7.62 m) acted as a disruptive event and shifting point in the shoreline trend. As a response to that storm, major erosive processes occurred along the delta that caused an average shoreline retreat of 47 m. A progressive recovery during the spring and summer was mainly associated with periods of low wave energy. Nevertheless, by the end of the year a complete recovery had been achieved for about half of the coast, while the other half showed an average erosion of more than 10 m when compared to the pre-storm situation. Both the erosive and the recovery processes took place unevenly on different sections of the coast, probably dependent on factors such as the orientation of the beach and the pattern of longitudinal sediment transport along the coast.

Evolution of sandy shores under the combined impact of global climate change and anthropogenic activities in Shandong Peninsula, East China

Most sandy shores (SSs) are currently experiencing erosion to various degrees due to the combined impact of increasing climate change and human activities. In order to reveal the evolution of the SSs in the Shandong Peninsula (SP), shoreline and elevation changing data are obtained from 29 SSs and results show that most (27 of 29) of the SSs exhibited erosion. The length of the SSs has decreased by 241.4 km from 2010 to 2020, and the average shoreline recession rate was found to be 1.0 m/a and the downward erosion rate was in the range of 0.05 to 0.10 m/a. Climate change-induced sea level rise has a smaller effect on the erosion in the short term and the construction of massive coastal engineering structures has become a major cause of local coastal erosion. The coastal erosion rate caused by river damming and sand mining in the early years has abated and reduced seaward sediment transport induced by the expansion of the built-up area has become a new factor of coastal erosion. In the past decade, the 672 km2 net increase in land area mainly originated from human activities, has occupied the original space for hydrodynamic energy dissipation, which has severely disrupted the balance between sediment supply and the hydrodynamic environment and the system then rebalance itself by eroding unprotected SSs. Therefore, with the increase in hydrodynamic forces caused by climate change and the scarcity of sediment supply caused by human activities, continued erosion is expected to occur in the SSs.

Analysis of Shoreline Change of North Central Timor Regency, Indonesia

Shoreline change is a process that occurs due to the impact of natural factors and human activities. Geographically, the coastal area of North Central Timor Regency (NCT) is in the northern part of the island of Timor, East Nusa Tenggara Province (ENT). Physically, the area is affected by the oceanographic dynamics of the Sawu Sea waters and aquaculture activities, which impact the damage to coastal ecosystems. This study aims to analyze shoreline change in the northern coastal area of NCT Regency. The data used are Landsat 8 images from 2015-20221 to describe current conditions. Meanwhile, Landsat 5 imagery data from 1990 - 2000 was used to describe the initial conditions. The satellite imagery is analyzed to map shoreline changes that experience accretion or abrasion. The results show that the shoreline of the study area has experienced changes in accretion and abrasion. Based on the area of change in the northern coastal area of NCT Regency, the dominant accretion area was 1108.07 m2 with a rate of change of 20.19 m.year-1, as long as 1021 meters, while the abrasion was 845.43 m2 at a rate of 12.65 m.year-1 as long as 36520 meters. The average shoreline change distance in accretion conditions was 11.3 meters, while the abrasion was 7.93 meters. The shoreline shift due to the highest abrasion in Ponu was -16.08, while accretion in North Oepuah was 35.63 meters. The results of this research will contribute to planning the management of the coastal area of NCT Regency.

Shoreline Changes from Erosion and Sea Level Rise with Coastal Management in Phuket, Thailand

Phuket, the study area of this work with 33 sandy beaches, provides about 15% of the nation’s gross domestic product from the tourism industry. Many factors cause shoreline changes affecting beach areas, such as seasonal erosion and rising sea levels. In this study, shoreline position was the key parameter for evaluating shoreline changes. The CoastSat open-source software was selected to analyze the shoreline changes using a publicly available satellite imagery API. The future shoreline recession was projected using the Bruun rule integrated with field observation data and sea level rise scenarios from Coupled Model Intercomparison Project Phase 6 (CMIP6). The result indicated that eight of the study site’s locations were under mild erosion from 2013 to 2021. The average shoreline change varied between −4.10 and 5.47 m/year. The projection of future beach loss due to sea level rise found that 20 beaches and 32 beaches will be lost entirely under SSP1 2.6 and SSP5 8.5, respectively. Beach morphology is influenced by human-induced activities, such as coastal urbanization and the development of structures along the coast. This study discusses the effectiveness of the present coastal protection structure with data from field observations and suggests possible future management strategies.

A quantitative analysis of multi-decadal shoreline changes along the East Coast of South Korea

South Korea's east coast is facing several issues related to coastal erosion because of sea-level rise, typhoon-induced storm surges, and various coastal development projects. In recent decades, high storm waves have frequently appeared on the east coast, causing casualty, beach erosion, and coastal infrastructure damage, drawing significant public attention. Thus, we analyzed the multi-decadal shoreline changes to understand the coastal dynamics and the forces responsible for the spatio-temporal changes along the 173 km coastline. The shorelines covering 38 years between 1984 and 2022 were derived from Landsat images and the change statistics, i.e., linear regression rate (LRR), endpoint rate (EPR), weighted linear regression (WLR), and net shoreline movement (NSM), were calculated at a 100 m alongshore intervals using Digital Shoreline Analysis System (DSAS), revealed several distinct behaviors of shoreline position. The long-period (1984–2022) assessment showed an average shoreline change rate (LRR) of 0.17 m/year with an estimated mean erosion and deposition rate of −0.57 and 2.07 m/year, respectively. The long-term surface gain and loss of the backshore region exhibited that the net surface gain of the east coast is 421.13 ha, and the net loss is 181.82 ha. The assessment of decadal shoreline changes showed a cyclic pattern of erosion (from 1984–1990 and 1999–2010) and accretion (from 1990–1999 and 2010–2022). Furthermore, a secondary level of investigation was conducted to address a wider variety of coastal behaviors by segmenting shoreline change rates based on coast types and average slopes along coastlines. It was observed that the frequent coastal deformation is associated with a flatter beach compared to a steep one. This study found that the artificial structures constructed along the east coast have not completely solved or stopped the erosion issues but shifted it from one location to another. The analysis of local and regional shoreline changes had shown that typhoon-induced storm surges, high storm waves, and anthropogenic activities like encroachment and the development of artificial coastal structures were the primary drivers of coastline changes along the east coast. Finally, we proposed a decision-making classification scheme that can be used to determine the mechanism of decision for protective and preventive measures against further coastal deterioration.

Shoreline Dynamics Assessment of Moheshkhali Island of Bangladesh using Integrated GIS-DSAS Techniques

Coastal areas of Bangladesh are more susceptible to the adverse effects of climate change due to their geographic location and geological condition. The coastal zones and offshore islands of the country have indisputably experienced the combined consequences of global temperature and sea level rise. Aiming to study and understand shoreline dynamics and shoreline change, medium resolution (30m) satellite imagery over 30 (1990-2020) years was being executed. The Digital Shoreline Analysis System (DSAS) in the GIS platform was used in conjunction with other geospatial techniques to ascertain shoreline dynamics in multiple satellite images taken over this period, and afterward, the spatial outcomes were validated through a detailed field investigation. The study demarcated that the shoreline of Moheshkhali is subjected to severe erosion and accretion and has undergone significant morphological changes. On the basis of average shoreline change rates, the island's shoreline is divided into 6 accretion zones and 4 erosion zones, with accretion being the dominant process. Accretion occurs in the south and south-western parts of the island, particularly those near the sea heads, which have experienced significant accretion at a rate of more than 86 m/yr and the consequent westward and south-east migration of the shore due to the active deposition along the coast. Besides, minor alterations were observed in the north and north-eastern part of the island. The study also evident that climate change, windy storms, variability in coast material, intermittent wave and air action, longshore transport, and anthropogenic activities are prime factors that contribute to the highly dynamic nature of the shorelines of Moheshkhali island. Therefore, this study demonstrates the benefit of using an integrated GIS-DSAS tool to investigate spatiotemporal shoreline change, and it might be valuable in land-use planning and coastal erosion mitigation on Moheskhali Island.&#x0D; The Dhaka University Journal of Earth and Environmental Sciences, Vol. 11(1), 2022, P 1-13&#x0D;

Improved geospatial analysis of shoreline modification using a weighted‐average‐based novel formulation

AbstractThis study presents a novel weighted‐average method (WAM) that captures the detailed nuances of shoreline change patterns over long and short periods by considering shorelines belonging to five different time frames. Using the WAM, the average shoreline modification for the longer period (136 years with intervals of ~34 years) and for the shorter period (annual changes over a period of 5 years) have been calculated for the 9 km stretch of the Kollam coast in Kerala, India. Historically, Kollam has been a prominent seaport on the Malabar Coast of India and was extensively mapped due to its importance for political, strategic, and trade reasons. The coastal information available in these older maps is unique as there are no comparable data for the coastline of that period that can be used to assess changes along the coast. The WAM demonstrated the efficacy of the historical maps as pivotal reference points. It reliably captured the different shoreline activities (i.e., growing, stable, and receding regions) of natural and anthropogenic origins within the study area, and the findings are consistent with results obtained by using the linear regression rate (LRR) and the end point rate (EPR) methods. This work presents both qualitative and quantitative analyses to evaluate shoreline change using various statistical and mathematical methods. The findings should serve as baseline information for coastal management, notably mitigating coastal hazards—whether of natural or anthropogenic origin—which could result in the enhancement of ecosystem services for coastal communities.

Analysis of shoreline changes along the coastal area of Biak Island (Biak Numfor Regency, Indonesia) using multitemporal Landsat images

&lt;h2 align="left"&gt;&lt;span style="font-size: 10px;"&gt;&lt;br /&gt;&lt;/span&gt;&lt;/h2&gt;&lt;p&gt;&lt;span style="font-size: 10px;"&gt;Monitoring shoreline changes is important in detecting abrasion and accretion in coastal areas. This study aimed to determine the level of shoreline change caused by abrasion and accretion and estimate the change rate. The study area covers coastal areas in ten Districts in Biak Numfor Regency (only on Biak Island). Six Landsat image datasets (1997, 2002, 2007, 2013, 2018, and 2022) were used to determine the coastline. Shoreline changes were analysed using DSAS software. The results of digitising the shoreline show a change in the length of the shoreline during the six data periods. Based on NSM and EPR for the last ten years (2013-2022), the average shoreline changes due to abrasion range from -6.65 to -13.16 m with an abrasion rate of -0.76 to -1.50 m/year. Meanwhile, the average shoreline changes due to accretion ranged from 4.64 to 8.45 m with an accretion rate of 0.53 m/year to 0.96 m/year. Changes in shoreline based on the rate of abrasion and accretion vary greatly in each district along the coastal area of Biak Numfor Regency, depending on the EPR value of each transect. Spatially, high abrasion and very high abrasion are widely distributed in Oridek, Biak Utara, Swandiwe, and Warsa Districts. Medium and high accretion were found in Yawosi, Bindifuar, and Oridek Districts. Because there has been a change in the coastline due to abrasion, planning efforts to mitigate coastal areas are very necessary. &lt;/span&gt;&lt;/p&gt;

Seven decades of shoreline changes along a muddy mangrove coastline of the Upper Gulf of Thailand

AbstractThis study evaluates the historical coastal change and development along the eastern coastline of the Upper Gulf of Thailand between 1953 and 2019 based on a series of aerial photographs and satellite images. Long‐term (~70 years) and short‐term (~10 years) shoreline movement rates were analysed using the Digital Shoreline Analysis System (DSAS). Results of this analysis indicate that the shoreline along the western coast (WBK) of the Bang Pakong River mouth has undergone severe coastal degradation, with a land loss of about 980 ha over the last seven decades. Meanwhile, the eastern coastline (EBK) has developed continuously over this time span, resulting in a land growth of about 552 ha. Based on historical shorelines recorded since 1954, the shoreline recession along the WBK coast accelerated over five decades. The average shoreline change rate reached approximately −9 m/year in 2002 and is shown to be related to land subsidence, which was due to groundwater withdrawals. The WBK coastline stabilized in 2009 and became an accretionary coast after 2016 due to the introduction of engineered coastal protection measures. In addition, the construction of major dams on the Chao Phraya and Bang Pakong rivers did not result in severe shoreline recession along the WBK coast. A significant reduction in sediment supply to the coastal zone due to damming was not observed. In contrast, the EBK coastline has advanced continuously since 1953, with average growth rates between 0.5 and 7.6 m/year over 50 years as a result of increased riverine sediment supply. Our results also indicate that mangrove deforestation was not a major factor causing shoreline retreat, and mangrove reforestation was not a successful coastal protection approach in this coast.

Climate change driven shoreline change at Hasaki Beach Japan: A novel application of the Probabilistic Coastline Recession (PCR) model

Low elevation coastal zones around the world are increasingly threatened by the effects of climate change, and adaptation in these areas is becoming urgent. One of these threats, especially to sandy beaches, is the slow chronic landward movement of the coastline, known as coastal recession. The Probabilistic Coastline Recession (PCR) Model is a physics-based approach that is specifically designed to support modern day risk informed coastal zone management. Here, the PCR model is applied at the highly monitored Hasaki Beach in Japan, which presents challenges that have hitherto not been experienced in previous applications of the model elsewhere in the world (e.g. lack of a clear correlation between high wave events and beach erosion, no storm erosion of dunes but only of the beach strong seasonal variation in erosion events). Therefore, the model is here applied following a novel approach to derive projections of coastal recession (here indicated by shoreline retreat) at Hasaki, under the two end-member IPCC scenarios (RCP 2.6, RCP 8.5.)Shoreline retreat is computed in two different ways that may be useful for two different management purposes; method (a) for computing the probability of erosion reaching and damaging an infrastructure or settlement at any time, and method (b) for computing the average shoreline retreat by a certain future time horizon. Projections for the end of the 21st century obtained with PCR method (a) indicate median shoreline retreats of 17 m (RCP 2.6) and 29 m (RCP 8.5), while those obtained with PCR method (b) are −15 m (RCP 2.6) and −7 m (RCP 8.5) (positive values indicate retreat and negative values indicate progradation). Bruun rule projections, which are comparable with those obtained from PCR method (b), indicate end-century shoreline retreats of 36 m and 66 m at Hasaki, for RCP 2.6 and RCP8.5 respectively. These projections fall at around 34% and 21% exceedance probability PCR method (b) projections respectively, consistent with several previous studies which also show that Bruun rule provides larger coastal recession projections compared to the PCR model. Furthermore, the Bruun Rule appears to provide increasingly conservative (relative to the PCR model) recession projections with increasing time horizons.

The Shoreline Deformation in Convex Beach due to Sea Level Rise

Sea level rise (SLR) is become more serious on a global scale and has become one of the main reasons causes shoreline changes, and erosion, even on an extreme scale can cause the sinking of coastal areas and islands. It was recorded that many big cities were damaged by SLR. The Bruun rule is the most widely used method for predicting the horizontal translation of the shoreline associated with a given rise in sea level. In this study, however, the change in the average shoreline at the convex beach, which is more vulnerable to erosion due to sea level rise, is investigated. The increase in water depth by sea level rise causes a change in the wave crestline, ultimately leading to a linearization of the shoreline. In general, it is assumed that the annual average shoreline is parallel to the annual mean wave crestline. Moreover, assuming that the equilibrium depth contour is formed according to the crestline, the retreat of the shoreline is predicted. The shoreline change is indirectly predicted through the wave crestline deformation obtained from a wave model and this method is applied to the convex beach. Our result showed that for a convex beach with a length of 1 km has open ends with free littoral drift at both ends, the sea level rise of 1 m cause the erosion of 10 m in the protruding area, and the sea level rise of 2 m causes erosion of 23 m. However, if the convex beach is blocked at both ends, sea level rise of 1 m causes the erosion of 6.3 m in the convex area, but the shoreline advance of 3.8 m at both ends, and if the sea level rise of 2 m occurs, the erosion of 14.3 m can occur in the convex area and shoreline advance of 8.6 m can occur at both ends.

Asymmetry between Accretional Advance and Erosional Retreat of Shoreline Position in On-offshore Direction

Yoo, H.J.; Kim, H.; Lee, J.L., and Park, J.Y., 2021. Asymmetry between accretional advance and erosional retreat of shoreline position in on-offshore direction. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 6–10. Coconut Creek (Florida), ISSN 0749-0208. Episodic shoreline retreat often slowed recovery in low frequency periods (weeks or months). The asymmetry between wave energy rise and collapse is closely related to the asymmetry of shoreline advancement and retreat, but the latter is more pronounced due to the different profile adjustment processes. Long-term wave time series data and shoreline time series data were analyzed at Won-pyeong beach located on the east coast of Korea. When waves such as storms come into the beach, the shoreline quickly retreated, and in relatively quiet times, the beach slowly recovered to it's original position. Also, the asymmetry of the shoreline position with respect to time is stronger than that of the wave height. A methodology is proposed here, and the envelope rope curve can be used to predict profile and average shoreline changes in the reference section for erosion steps such as storms.The proposed equation was in good agreement for shoreline asymmetry position, and is satisfactory. Empirical formular are slightly different in the relatively calm period, this is an artificial change formed by external pressure conditions such as artificial nourishment. Several variables were used as correction factors. It`s important for future research to propose standardized correction factors and ranges by applying them at various sites.

Analysis of Beach Changes after Construction of Submerged Breakwaters

Lee, H.; Kim, J.; Chang, S., and Kim, I., 2021. Analysis of beach changes after construction of submerged breakwaters. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 300–304. Coconut Creek (Florida), ISSN 0749-0208. This study presents seasonal investigations of submerged breakwaters constructed from 2013 to 2014 as part of a government erosion prevention project in the region of Samcheok-si, South Korea. Parameters, including wave-induced currents, wave heights, beach profiles, and shoreline changes, were investigated to monitor and analyze sand transport trends in the study area. The construction of Gungchon Harbor in 2006 led to the transport of sand from southern Wonpyeong Beach to northern Gungchon Beach, which resulted in an average shoreline retreat of greater than 50 m. However, despite the subsequent construction of the submerged breakwaters, beach erosion continued to occur in adjacent areas. Specifically, a tombolo was generated behind the submerged breakwaters, which led to beach erosion. Rip currents were also typically generated near submerged breakwaters, which play a role in the offshore transportation of sand. Wonpyeong Beach experienced erosion following the construction of Gungchon Harbor, whereas Gungchon Beach exhibited accretion. Moreover, evidence of further erosion was observed near the breakwater construction area. Therefore, this study indicates that detailed monitoring during and after the construction of breakwaters is required to predict potential secondary erosion and understand the erosion mechanism for an optimal breakwater design.

EXPLORATION OF HELOPHYTE GROWTH DYNAMICS IN THE PSKOVSKOE LAKE LITTORAL ZONE USING REMOTE SENSING DATA

The article presents the results of an assessment of the spatio-temporal dynamics of the Pskovskoe Lake littoral zone overgrowing with helophytes in the period from 1989 to 2019. Lake Pskovskoe is a shallow body of water with a high trophic status, annual water level fluctuations, and an extensive littoral zone (about 15 % of the water surface area). The said factors, coupled with global warming, create favorable conditions for the expansion of higher aquatic vegetation. A detailed analysis of the history of research of the lake water area is provided. The types of the lake overgrowing in different years with indication of the prevalent ecological groups and dominant species are suggested. Lake Pskovskoe is characterized by the helophytic – “fragmentary-belt” type of overgrowing. Data from the literature and own field data were analyzed; multispectral satellite images taken in different years were thematically processed. The process of littoral overgrowing in this period has been fluctuating, with a positive trend component. In low-water years, the occurrence of helophytic plants increased. The expansion of helophytes in relation to the averaged shoreline configuration ranged from 26.56 to 641.9 ha, i. e. 0.04–0.9 % of the lake total area. The largest helophyte expansion was noted at Talabsk station, where the overgrown area gained 7.5 hectares in the period from 2007 to 2017. Amongyear changes of the main structural parameters of the southern reed (Phragmites australis (Cav.) Trin. Et Steud., 1840), the species playing the key role in the overgrowing of Lake Pskovskoe, are analyzed. The density and biomass of the reed stands have increased over the period of observations.

The Role of Thermal Denudation in Erosion of Ice-Rich Permafrost Coasts in an Enclosed Bay (Gulf of Kruzenstern, Western Yamal, Russia)

Coastal erosion in the Arctic has numerous internal and external environmental drivers. Internal drivers include sediment composition, permafrost properties and exposure which contribute to its spatial variability, while changing hydrometeorological conditions act as external drivers and determine the temporal evolution of shoreline retreat. To reveal the relative role of these factors, we investigated patterns of coastal dynamics in an enclosed bay in the southwestern Kara Sea, Russia, namely the Gulf of Kruzenstern, which is protected from open-sea waves by the Sharapovy Koshki Islands. Using multitemporal satellite imagery, we calculated decadal-scale retreat rates for erosional segments of the coastal plain from 1964 to 2019. In the field, we studied and described Quaternary sediments and massive ground-ice beds outcropping in the coastal bluffs. Using data from regional hydrometeorological stations and climate reanalysis (ERA), we estimated changes in the air thawing index, sea ice-free period duration, wind-wave energy and total hydrometeorological stress for the Gulf of Kruzenstern, and compared it to Kharasavey and Marre-Sale open-sea segments north and south of the gulf to understand how the hydrometeorological forcing changes in an enclosed bay. The calculated average shoreline retreat rates along the Gulf in 1964–2010 were 0.5 ± 0.2 m yr−1; the highest erosion of up to 1.7 ± 0.2 m yr−1 was typical for segments containing outcrops of massive ground-ice beds and facing to the northwest. These retreat rates, driven by intensive thermal denudation, are comparable to long-term rates measured along open-sea sites known from literature. As a result of recent air temperature and sea ice-free period increases, average erosion rates rose to 0.9 ± 0.7 m yr−1 in 2010–2019, with extremes of up to 2.4 ± 0.7 m yr−1. The increased mean decadal-scale erosion rates were also associated with higher spatial variability in erosion patterns. Analysis of the air thawing index, wave energy potential and their total effect showed that inside the Gulf of Kruzenstern, 85% of coastal erosion is attributable to thermal denudation associated with the air thawing index, if we suppose that at open-sea locations, the input of wave energy and air thawing index is equal. Our findings highlight the importance of permafrost degradation and thermal denudation on increases in ice-rich permafrost bluff erosion in the Arctic.

A DSAS-based study of central shoreline change in Jiangsu over 45 years

A large-scale sand ridge group is distributed in the central Jiangsu coastal area, and a deposition muddy sea bank was developed in the nearshore area. Quantitative monitoring of coastline changes is of great significance for tidal beach development and protection. The shorelines of the central coast of Jiangsu within six periods (1973–2018) were extracted in this study, and their length changes over the years were analyzed. The Digital Shoreline Analysis System (DSAS) was employed to generate a cross section perpendicular to the baseline and calculate the linear regression rate (LRR) of the shoreline, changes in end point rate (EPR), and net shoreline movement (NSM), based on which the shoreline change features were analyzed. The DSAS results indicated that the shorelines in the study area maintained fluctuating growth and presented a continuous advancing trend towards the sea. From the changes in shoreline evolution distance during 1973–2018, the advancing shorelines in the study area accounted for over 50% of the total shorelines and presented first rising and then declining trends with the period of 2003–2013 taken as the time boundary. The average shoreline change rate was 207 m/year, and the periods with the highest change degrees were 1983–1993 and 1993–2013. The shoreline change tended to be stable during 2013–2018, and only a few estuaries and ports underwent obvious erosion and sedimentation.