Long-term Coastal Erosion Research Articles

Arctic coastal hazard assessment considering permafrost thaw subsidence, coastal erosion, and flooding

The thawing of permafrost in the Arctic has led to an increase in coastal land loss, flooding, and ground subsidence, seriously threatening civil infrastructure and coastal communities. However, a lack of tools for synthetic hazard assessment of the Arctic coast has hindered effective response measures. We developed a holistic framework, the Arctic Coastal Hazard Index (ACHI), to assess the vulnerability of Arctic coasts to permafrost thawing, coastal erosion, and coastal flooding. We quantified the coastal permafrost thaw potential (PTP) through regional assessment of thaw subsidence using ground settlement index. The calculations of the ground settlement index involve utilizing projections of permafrost conditions, including future regional mean annual ground temperature, active layer thickness, and talik thickness. The predicted thaw subsidence was validated through a comparison with observed long-term subsidence data. The ACHI incorporates the PTP into seven physical and ecological variables for coastal hazard assessment: shoreline type, habitat, relief, wind exposure, wave exposure, surge potential, and sea-level rise. The coastal hazard assessment was conducted for each 1 km2 coastline of North Slope Borough, Alaska in the 2060s under the Representative Concentration Pathway 4.5 and 8.5 forcing scenarios. The areas that are prone to coastal hazards were identified by mapping the distribution pattern of the ACHI. The calculated coastal hazards potential was subjected to validation by comparing it with the observed and historical long-term coastal erosion mean rates. This framework for Arctic coastal assessment may assist policy and decision-making for adaptation, mitigation strategies, and civil infrastructure planning.

Initial shape reconstruction of a volcanic island as a tool for quantifying long-term coastal erosion: the case of Corvo Island (Azores)

Abstract. Long-term coastal erosion is not yet well studied given that it is difficult to quantify. The quantification of long-term coastal erosion requires reconstruction of the coast's initial geometry and the determination of where and when the erosion started. Volcanic islands fulfill these two conditions: their initial shape is roughly conical and the age of the lavas that generated this geometry is easily measured. We have developed a method to reconstruct the initial shape of simple volcanic edifices from aerial and submarine topographic data. The reconstructed initial shape and associated uncertainties allow us to spatially quantify the coastal erosion since the building of the island. This method is applied to Corvo Island in the Azores archipelago. We calculated that, due to coastal erosion, the island has lost a volume of 6.5 ± 2.7 km3 and roughly 80 % of its surface area since it first came into being. Taking the large uncertainty in the age of the topmost lava flows (0.43 ± 0.34 Myr) into account, we have estimated that Corvo Island has lost an average of 5000 to 100 000 m3 yr−1 of its volume due to coastal erosion. Lastly, we show a strong correlation between long-term coastal erosion and the spatial distribution of the waves. Specifically, we highlight a stronger control on erosion by smaller and more frequent waves than by storm waves. The next step will be to apply this method to other volcanic islands in order to (i) streamline and improve the method and (ii) verify the correlations observed in the present study.

Coastal chalk cliff retreat rates during the Holocene, inferred from submarine platform morphology and cosmogenic exposure along the Normandy coast (NW France)

Submerged marine terraces potentially provide crucial information on past sea-level variations and paleo-coastline locations that may be used to estimate long-term coastal erosion rates. The Normandy coastline has recently been surveyed using a shallow water high-resolution mapping system. We identified a new continuous submarine platform, called the inner platform, limited by a shore parallel edge located between -9 m and -10 m (NGF) along the Normandy chalk coastline. A lower rock platform, called the outer platform, ranging from about -14 m to -17 m (NGF) appears locally. This corresponds to inherited preserved submarine terraces created during a past sea level highstand. The high cosmogenic 10Be concentration measured at the end of Mesnil-Val inner shore platform (including intertidal and subtidal shore platforms) is attributed to the last glacial cliff location at 6.5 ky ± 1 ky. From the spatial edge location of the inner platform in Normandy, we estimated cliff retreat rates since 6.5 ky ± 1 ky ranging from 0.051 ± 0.008 m/y to 0.090 ± 0.014 m/y from place to place. Comparisons with the current coastal chalk cliffs indicate a mean retreat rate estimated over the contemporary period suggesting such long-term retreat rates are 33% to 57% lower than the contemporary ones (0.10 m/y to 0.18 m/y). This confirms a contemporary acceleration of chalk cliff system retreat rates.

Estimation of Background Erosion Rate at Janghang Beach due to the Construction of Geum Estuary Tidal Barrier in Korea

In this study, a reduction in sediment budget due to the development of a river watershed, resulting in coastal erosion, was reviewed, and the rate of background erosion was calculated through an examination of the loss of coastal sediment into the open sea. The west coast of the Korean peninsula is severely impacted by the intercept of inflowing sediments from rivers, owing to the watershed development. However, the effects have not fully propagated into the entire coastal area, and thus, the long-term coastal erosion remains insignificant. However, a serious and irrevocable disaster may occur once the coastal erosion begins. Therefore, an analysis of the coastal erosion resulting from changes in the sediment budget, due to the development of the watershed, was conducted on Janghang Songrim Beach. A littoral cell of the Geum River was selected for a quantitative analysis of the decrease in the sediment budget from the watershed development. The rate of coastal sediment loss offshore, which reflects the characteristics of the Janghang Songrim Beach, and the future rate of coastal erosion were calculated. Then, the results were verified by employing geometrically corrected satellite photographs from previous years. This will enable us to predict the time of coastal erosion in the future due to a reduction in the sediment budget and watershed development, and prepare for future disasters resulting from the coastal erosion. Based on research into the components constituting the coastal development, the present study presents theoretical formulae allowing the prediction of the sediment budget and providing a practical contribution to the prevention of coastal erosion, for which additional reliable studies need to be conducted.

Changes in the Littoral Drift System of the Uruguayan Coast during the Holocene and its Influence in the Continuing Erosion in Southern Brazil

Dillenburg, S.R.; Barboza, E.G.; Rosa, M.L.C.C.; Caron, F., and Bitencourt, V.B., 2020. Changes in the littoral drift of the Uruguayan coast during the Holocene and its influence in the continuing erosion in southern Brazil. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 453–457. Coconut Creek (Florida), ISSN 0749-0208.In northern Uruguay and southern Brazil, a littoral drift system dominates from southwest to northeast. This littoral drift is a consequence of higher wave-energy, generated in southern latitudes and that has been operating on a long-term scale, playing an important role not only in the evolution of coastal barriers of this region during the Holocene but also in coastal erosion that presently occurs in some parts of this coast. From La Coronilla to Cabo Santa Marta, which is a coastal sector 750 km - along the coast is gently undulating, showing gentle projections located to the south of gentle reentrances, that are dominated by transgressive/stationary and regressive barriers, respectively. In general, the regressive barriers have been developed by sediments brought into the reentrances by long-shore currents. The main source of these sediments had been the transgressive/stationary barriers that occur along the coastal projections. This differentiation of barrier behavior started at around 6-5 ka, at the end of the Postglacial Marine Transgression (PMT), when all rivers were drowned, finishing the delivery of new coarse sediments to the coast. Also, at this time the large rock promontories of the Uruguayan coast were formed and started to retain sediments of the littoral drift system, triggering a long-term coastal erosion in the southernmost coastal projection. Regarding erosion that is occurring in this stretch of coast the important issue to be considered in future coastal planning is that erosion will continue to operate in the long-term but will also be (and certainly has been already) amplified by sea-level rise in the next centuries as projected by the Intergovernmental Panel on Climate Change (IPCC).

Climate change impact and vulnerability assessment of Mumbai city, India

Climate change (CC) is one of the most challenging problems of today which need to be understood. CC impact studies at the urban centres are the need of the hour. Mumbai is one of the most vulnerable port cities in the world and one of the most densely populated cities in the world. The city is vulnerable to CC-induced hazards, including sea-level rise, storm surge, flooding, and coastal erosion. In this study, it is tried to do the spatial integration of vulnerability from these hazards to portray the overall CC-induced impacts in Mumbai city. This study portraits the overall vulnerability of the Mumbai megacity, considering SLR, long-term coastal erosion, and flooding. This integrated vulnerability assessment reveals that 123.35 km2 (24%) of the Mumbai regions is demarcated as composite vulnerable regions. They are mostly around the coastal tracts. Within the vulnerable regions, inland flood-affected areas from the past floods area are 37.13 km2, which is around 30% of the demarcated most vulnerable regions. Remaining vulnerable areas are falling in built up, barren, forest, vegetation, and mangrove regions. The most worrying impact would be in the 44 km2 of the built-up areas, which is around 35% of the vulnerable regions. It pulls the city to one of the most vulnerable cities of the world due to the exposure of the higher population. Rest of all the classes can cope up as they are naturally covered, not covered, and the human population is not residing over those regions currently. Since the city is expanding rapidly, other LULC classes apart from built-up land have to be converted based on the need. Available barren land can be kept for rehabilitation in the future. This study provides vital information about the CC-induced vulnerability of Mumbai city.

Long-term coastal erosion assessment along the coast of Karnataka, west coast of India

Coastal areas are always under frequent threat from various natural processes and man-induced activities. Coastal erosion is recognized as the permanent loss of land along the shoreline resulting in the transformation of the coast. The current study focuses on long-term coastal erosion analysis of the entire Karnataka coast using Remote Sensing, Geographical Information System (GIS), Linear Regression Rate (LRR), and End Point Rate (EPR) techniques. Analysis of 26 (1990 to 2016) years of erosion using Landsat images by the use of the Digital Shoreline Analysis System (DSAS) tool has been done. The results show a high erosion rate at Ullal during this period (LRR -1.3 m/yr) and accretion at Devbagh (LRR 3.2 m/yr). The southern Karnataka coast faces severe erosion especially at Ullal, where the settlement is high. At Thanirbhavi, Mukka, Kota, and Om Beaches erosion also is noticed. Both anthropogenic activities like ports, seawalls, breakwaters, etc. and natural processes like long shore drift, seasonal variation, etc. are factors affecting the shoreline change along the Karnataka coast.

Shoreline morphology changes along the Eastern Coast of India, Andhra Pradesh by using geospatial technology

Shoreline changes on account of global climate change and sea level rise is one of the major problems along the coastlines in different continents of the world. This study was carried out along the coastlines of Andhra Pradesh state in India using multi-temporal satellite images from 1973 to 2015 period. Long-term coastal erosion and accretion rate over a period of 42 years has calculated using Digital Shoreline Analysis System and prepared shoreline maps by using GIS-Software. End point rate (EPR) statistical method is applied to estimate the shoreline change rate. Various coastal parameters like sea level rise, geomorphology, elevation and coastal slope were used to find out the interactive relationship between the physical parameters and shoreline changes in the area. The study revealed that the coastal changes are more dominant in Krishna and Godavari Deltaic plain. The average erosion and accretion rate observed in the Krishna Godavari delta was 10.63 and 17.29 m per year respectively. The study indicated that, climatic changes and fluvial process are playing key role in changing shoreline positions. The study exhibited that elevation and slope are played intense role in the shoreline positional change. The present study demonstrates that combined use of satellite imagery and EPR statistical method as an accurate and reliable method for shoreline change analysis.

Coastal Morphodynamics of Tupilipalem Coast, Andhra Pradesh, Southeast Coast of India

Coastal zones are dynamic interfaces of land and water of high ecological diversity and critical economic importance. The boundaries, shape and size of this coast change constantly under the influence of both natural and anthropogenic factors. The study area, Tupilipalem is one of the proposal sites for constructing a major port, to be named Dugarajapatnam Port, along the east coast of Andhra Pradesh, India. We have used multitemporal satellite images of IRS P6 LISS-III and Landsat 8 OLI/TIRS data from 2011 to 2015 to delineate changes in Tupilipalem coast. The subsequent short-term lagoon mouth closure and the long-term coastal erosion and accretion rates have been calculated for the periods between 2011 and 2015. Low river inflow, wind, tides, the movement of the waves and littoral currents play a key role in the closure of the lagoon mouth and also for the dynamic activities of erosion and accretion. Moreover, the impact on socio-economy and ecology of the study area during the lagoon mouth closure period has been studied.

Evolution of paraglacial coasts in response to changes in fluvial sediment supply

Abstract Paraglacial coastal systems are formed on or proximal to formerly ice-covered terrain from sediments with direct or indirect glacial origin. This review addresses the roles of tectonic controls, glacial advances and retreats, sea-level changes, and coastal processes in sediment production, delivery and redistribution along the paraglacial Gulf of Maine coast (USA and Canada). Coastal accumulation forms are compositionally heterogeneous and found primarily at the seaward edge of the Gulf's largest estuaries; their existence is directly attributable to the availability of glacial sediments derived from erosion of weathered plutons within coastal river basins. Multiple post-glacial sea-level fluctuations drove the redistribution of these sediments across the modern lowland and inner shelf. Central to the formation of barrier systems was the paraglacial sand maximum, a time-transgressive phase of relative sea-level fall and enhanced fluvial sand export c. 2000–4000 years following deglaciation. Vast quantities of sand and gravel were reworked landward during the subsequent transgression and combined with additional riverine sediments to form the modern barrier systems. Today, reduced fluvial sediment loads, anthropogenic modifications of barrier and river systems, and sea-level rise have combined to exacerbate long-term coastal erosion and may eventually force these barriers toward a state of rapid landward migration.

Evaluation of coastal erosion and accretion processes along the southwest coast of Kanyakumari, Tamil Nadu using geospatial techniques

The impact of coastal erosion has adversely affected the socioeconomic conditions of the coastal community worldwide. The coastal environment is experiencing a wide range of natural and anthropogenic pressure in India. This study was carried out along the southwest coast of Kanyakumari, South India using multitemporal Landsat satellite images from 1999 to 2011. The long-term coastal erosion and accretion rates have been calculated for the periods between 1999 and 2011, and the subsequent short-term changes were performed during 1999–2000, 2005–2006, and 2010–2011. Thus, the long-term coastal changes indicate that the net erosion rate is higher on the coasts of Kanyakumari, Kovalam, Manavalakurichi, Mandaikadu, and Thengapattinam; the values are 0.118, 0.105, 0.127, 0.133, and 0.017 m2, respectively. Meanwhile, the annual erosion rate of these areas is 10,000, 9,000, 11,000, and 1000 m2/year. The coastal zones Ganapathipuram and Enayamputhandurai have experienced accretion; the net accretion rate is 0.271 and 0.081 m2, respectively. Coastal beaches, beach ridges, and marine terraces are predominantly disturbed by the hydrodynamic processes including wave action, littoral current, and intervention of littoral drift by the artificial coastal structures like groins, revetments, and seawalls. Moreover, the study area has been demarcated with site-specific erosion and accretion zones based on the frequent seaward or landward coastline fluctuation through geospatial technique.

The influence of shelf-indenting canyons and infralittoral prograding wedges on coastal morphology: The Carchuna system in Southern Spain

Abstract Submarine canyons and progradational sedimentary bodies are common features of continental margins worldwide. Few studies have analyzed the relationship between the coastal morphology and the morphology and sedimentary characteristics of the adjacent shelf in wave-dominated coasts; or the potential role played by shelf-indenting canyons as inducers of sediment deposition in shallow waters. This work presents a study that correlates the coastal morphology with the characteristics of the adjacent offshore shallow shelf in an area with a complex inner bathymetry: the Carchuna system, Spain. The study area is characterized by large-scale non-rhythmic cuspate features in the coastline, whereas the inner bathymetry exhibits a shallow-water infralittoral prograding wedge (IPW) and a shelf-indenting canyon that has tributaries located a short distance from the coastline. Using detailed bathymetric measurements, observational data and wave propagation modeling, the influence of the different bathymetric elements was quantified, and a mechanism proposed for the generation of the Carchuna IPW. The wave propagation results show that the canyon is the main source of the alongshore modulation of nearshore waves and that it plays a major role in the generation of the large-scale cuspate features in the shoreline. Additionally, these results suggest that the long-term coastal erosion associated with extreme storms yielded sufficient sediment which when subsequently transported eastward, the dominant littoral drift direction, formed the IPW. Once formed the IPW modified the wave propagation patterns and contributed to the development and reinforcement of the shoreline features.

Regulatory Takings and Property Rights Confront Sea Level Rise: How Do They Roll?

Under the Beach and Shore Preservation Act, the State of Florida is authorized to conduct extraordinarily expensive beach renourishment projects to restore damaged coastal properties. The statute advances the State’s interest in repairing the damage to the coastal ecosystem and economy caused by hurricanes, high winds, and storm surges. The effect of a renourishment project conducted under the statute is to fix the legal boundary of the littoral property owner at an Erosion Control Line. Plaintiffs in Walton County v. Stop the Beach Renourishment, Inc. claimed that the statute took their common law property rights to their boundary, which would, but for the Act, move gradually landward or seaward, maintaining contact with the water. The Florida Supreme Court disagreed and the U.S. Supreme Court granted certiorari in Stop the Beach Renourishment, Inc. v. Florida Department of Environmental Protection to determine whether the state court reinterpreted Florida’s common law as a pretext for upholding the statute against the plaintiffs’ taking claim and, if so, whether that reinterpretation constituted a “judicial taking.” The Court ultimately decided that the Florida court’s interpretation was correct and that there was no regulatory taking. A majority of the Court could not agree as to whether a state court’s interpretation of state common law could constitute a “judicial taking.” This article discusses greenhouse gas emissions, global warming, sea level rise, and the ferocity of coastal storms associated with climate change. It explores the tension between these movements in nature and the policy of the State of Florida to fix property boundaries, which under common law would move landward as sea level rises. The property rights and title to land of littoral landowners are described and the effect of the Beach and Shore Preservation Act on them discussed. The article contrasts the Florida coastal policy regarding beach and shore protection with the policies and programs of federal, state, and local governments that use other approaches such as accommodating rolling easements, prohibiting shoreline armoring, requiring removal of buildings, purchasing development rights or the land itself, and imposing moratoria on rebuilding after storm events. These may be less expensive and more realistic approaches to long-term coastal erosion and avulsive events and the inevitability of sea level rise as the climate warms and worsens. The article concludes with a recommendation that the framework for federal, state, and local cooperation in coastal management be revisited and strengthened so that the critical resources and knowledge are brought to bear on this critical issue. It suggests that strengthening those ties, rather than radically restructuring the relationship between state and federal courts, is a more productive method of meeting the needs of a changing society.

Looking for evidence of climate change impacts in the eastern Irish Sea

Abstract. Although storminess is often cited as a driver of long-term coastal erosion, a lack of suitable datasets has only allowed objective assessment of this claim in a handful of case studies. This reduces our ability to understand and predict how the coastline may respond to an increase in "storminess" as suggested by global and regional climate models. With focus on 16 km of the Sefton coastline bordering the eastern Irish Sea (UK), this paper analyses available measured datasets of water level, surge level, wave height, wind speed and barometric pressure with the objective of finding trends in metocean climate that are consistent with predictions. The paper then examines rates of change in shoreline position over the period 1894 to 2005 with the aim of establishing relationships with climatic variability using a range of measured and modelled metocean parameters (with time spans varying from two to eight decades). With the exception of the mean monthly wind speed, available metocean data do not indicate any statistically significant changes outside seasonal and decadal cycles. No clear relationship was found between changes in metocean conditions and rates of shoreline change along the Sefton coast. High interannual variability and the lack of long-term measurements make unambiguous correlations between climate change and shoreline evolution problematic. However, comparison between the North Atlantic Oscillation winter index (NAOw) and coastline changes suggest increased erosion at times of decreasing NAOw values and reduced erosion at times of increasing NAOw values. Erosion tends to be more pronounced when decreasing NAOw values lead to a strong negative NAO phase. At present, anthropogenic changes in the local sediment budget and the short-term impact of extreme events are still the largest threat likely to affect coastal flooding and erosion risk in the short- and medium-term. Nevertheless, the potential impacts of climate change in the long-term should not be ignored.

Study on headland-bay sandy coast stability in South China coasts

Headland-bay beach equilibrium planform has been a crucial problem abroad to long-term sandy beach evolution and stabilization, extensively applied to forecast long-term coastal erosion evolvement and the influences of coastal engineering as well as long-term coastal management and protection. However, little concern focuses on this in China. The parabolic relationship is the most widely used empirical relationship for determining the static equilibrium shape of headland-bay beaches. This paper utilizes the relation to predict and classify 31 headland-bay beaches and concludes that these bays cannot achieve the ultimate static equilibrium planform in South China. The empirical bay equation can morphologically estimate beach stabilization state, but it is just a referential predictable means and is difficult to evaluate headland-bay shoreline movements in years and decades. By using Digital Shoreline Analysis System suggested by USGS, the rates of shoreline recession and accretion of these different headland-bay beaches are quantitatively calculated from 1990 to 2000. The conclusions of this paper include that (a) most of these 31 bays maintain relatively stable and the rates of erosion and accretion are relatively large with the impact of man-made constructions on estuarine within these bays from 1990 to 2000; (b) two bays, Haimen Bay and Hailingshan Bay, originally in the quasi-static equilibrium planform determined by the parabolic bay shape equation, have been unstable by the influence of coastal engineering; and (c) these 31 bays have different recession and accretion characters occurring in some bays and some segments. On the one hand, some bays totally exhibit accretion, but some bays show erosion on the whole. Shanwei Bay, Houmen Bay, Pinghai Bay and Yazhou Bay have the similar planforms, characterized by less accretion on the sheltering segment and bigger accretion on the transitional and tangential segments. On the other hand, different segments of some bays have two dissimilar evolvement characters. Dacheng Bay, Shenquan Bay, Hudong Bay, Wukan Bay, Fengjia Bay, Wuchang Bay, Lingshui Bay and Tufu Bay produce accretion on the tangential segment, erosion on the transitional segment and accretion on the sheltering segment. However, Guang’ao Bay, Haimen Bay, Jinghai Bay, Sanya Bay(a), Dajiao Bay, Hailingshan Bay, Hebei Bay, Fuhu Bay, Shuidong Bay, Wangcun Bay and Bomao Bay generate erosion on the tangential part, accretion on the transitional part and accretion on the sheltering part. It seems to imply some relations between headland-bay beach evolvement and controls on headland-bay beaches, which may possibly to classify headland-bay beach types and should be further studied.

West Louisiana Chenier Plain History: ABSTRACT

The a-b-c ^hellip model, which is based on littoral transport of sand, provides a powerful method for coastal analysis. Where long-parallel beach ridges are present, however, it may not be applicable: the two-dimensional map-view model requires that dq/dx (a numerical evaluation of changes in the littoral drift load) not be zero, except at 3 sharply defined points, whereas long-parallel beach ridges were built under conditions where dq/dx was essentially zero at all points. These parallel beach ridges, then, do not represent an important littoral-drift system. Study of many sets of such ridges shows that they were built by onshore movement of sand which came from deeper water. The equilibrium which they achieve, with the passage of time, must be considered primarily in a vertical plane, taken at right angles to the beach, rather than in the map plane. They represent a steepening, with time, of an initially very gentle slope offshore from the beach, and leading to the suggestion that the present steeper slope is closer to equilibrium than the original gentle slope. The chenier plain of Cameron Parish, Louisiana, is composed mainly of parallel ridges. Because of the parallelism, as well as the large content of shell debris, it is thought that these cheniers were built of material which must be attributed to an offshore source. Because of local departures from parallelism, and the End_Page 1838------------------------------ presence of the Mississippi River heavy-mineral suite, these cheniers must have had a significant contribution from the littoral-drift system. It is concluded that much of the chenier plain, other than silt-clay mud swales, was built by onshore migration of sand which acquired its offshore location when sea level occupied a lower position. A plot of position versus age of the Cameron Parish cheniers indicates that growth of the plain has been slowing down, especially in the western part of the area, and that it may be close to a maximum width. The shoreface slope also may be close to a maximum angle. Both of these inferences suggest that the depositional history of this part of the coast may be essentially over, being replaced--either now or in the near future--by long-term coastal erosion. End_of_Article - Last_Page 1839------------