Changes In Coastal Geomorphology Research Articles

An updated reconstruction of Campi Flegrei caldera (southern Italy) ground deformation history and its interaction with the human sphere since Roman time

Since the 19th century, many scientists have tried to reconstruct the ground motions that occurred in the Campi Flegrei caldera, one of the most dangerous volcanos in the Mediterranean area. This study aims to assess the joint effects of vertical ground movements and anthropic forcing along the coasts of this volcanic area. A huge dataset of hundreds of archeo-stratigraphic boreholes was coupled with direct and indirect surveys of the main underwater archaeological sites scattered along the whole coastal sector and with the reinterpretation of bibliographic sources. Clear evidence of a differential volcano-tectonic behaviour (highlighted for the first time in this study) led us to divide the study area into three coastal stretches with homogeneous vertical ground movements. In each sector, a new relative sea-level (RSL) curve was reconstructed, by interpreting our stratigraphic and archaeological data in terms of SL markers covering a wider timespan compared to the previous studies, from the first Roman urbanization to the present day. The comparison between RSL curves and GIA models allowed estimating vertical ground movements (See Supplementary material 2) that occurred along the coast with decimetres accuracy. For each of the 5 recognized phase of uplift or subsidence, we also studied the subsequent effects in terms of coastal geomorphological change, and advantages or negative impacts on ancient human activities. We measured an overall subsiding trend that brought the RSL from −12 ± 1 m (4th century BC) to 7 ± 0.2 m during three different episodes between 5th and 15th centuries (1450–450 y BP), which was interrupted by short-lived falls (less of 100 years) of RSL. During the phases of RSL fall and/or volcano-tectonic stability, detected for the first time in the eastern and western part of the caldera (1st-2nd century AD and 3rd-4th century AD), a basinward shift of the coastline created newly emerged land even at the base of the local sea cliffs, where shore platforms emerged, favouring intense phases of urbanization on them along the Baia – Miseno sector and at the footslope of Rione Terra. This trend also favoured the closure of the Lucrino lagoon with an extended spit bar during the 2nd century BC, allowing the establishment of a large oyster farming system belonging to Sergio Orata. On the contrary, the subsiding phases resulted in the flooding of coastal areas and anthropic structures such as villas, nymphaea and ports inducing the construction of coastal protection structures. In the extreme case of Portus Julius, subsidence led to the abandonment of the military port and its move to nearby Miseno.

Geospatial techniques to determine Coastal geomorphology changes along the Cuddalore and Nagapattinam coast, Tamil Nadu, India

This study proposes to use geospatial techniques to assess coastal geomorphological changes along the southeast coast of India, from Cuddalore to Nagapattinam. The results will provide insights into regional morphology changes and will advance our understanding of coastal evolution, sea level variations and quaternary geomorphic processes. The coastal geomorphological units of the study area comprise of the coastal zone and an older deltaic plain. Most coastal zone features have developed through erosion, accretion and other natural processes. These features can be classified as depositional or erosional. By analyzing satellite imagery from 1980 to 2020, the study identified changes in coastal geomorphological features. This information can be used to locate mineral deposits, hydrocarbon locales, groundwater targets and sites for artificial recharge and saltwater intrusion mitigation. It can also affect coastal zone management decisions.

Evaluation and Modelling of the Coastal Geomorphological Changes of Deception Island since the 1970 Eruption and Its Involvement in Research Activity

Deception Island is an active volcano with a submerged caldera open to the sea called Port Foster. Several post-caldera-collapsed volcanic events, as well as hydrodynamics, have changed its inner coastline, shaping new volcanic deposits. A hydrodynamic model is presented to predict accretion and erosion trends in this bay, which could have an impact on the mobility of researchers and tourists. New historical orthophotos and spatio-temporal differences between digital elevation and bathymetric models were used for validation purposes. The model reveals that the south-facing coast is more susceptible to erosion, while the east- or west-facing coast experiences sedimentation. A visual study for the periods 1970–2003 and 2003–2020 in Port Foster obtained similar annual erosion/accretion lineal rates (0.3–2 m/year) in the areas not affected by the last eruptive period, as well as increases of 0.023 km2/year and 0.028 km2/year of the inner bay and coastal sedimentation rates of 0.007 km2/year and 0.002 km2/year, respectively. Only part of the significant total volume loss is received within the bay, including its own erosion, and accumulates on the bay bottom. This is largely because the volume input is composed of snow, and it is also due to the transfer of material outside to balance the figures.

Dynamic Changes in Coastal Geomorphology of Shiroda Coasts, using Remote Sensing and GIS: An Approach to Climate Change and Coastal Disaster Risk

The coastline is a unique land feature formed through the interaction between land and sea. It is essential to monitor and detect hotspots and observe spatial and temporal influences of climate change in the coastal environment. Coastal landform changes can be best studied through remote sensing data. This study examines the dynamic changes in the sand spit and associated coastal area of the Shiroda coasts of Sindhudurg district. The Normalized Difference Water Index (NDWI) was used to distinguish land and water and the area was calculated by reclassifying the NDWI index of all images with two classes- land surface of sand spit and water. It was found that the spit area is decreasing seasonally at a dynamic rate. Additionally, geomorphic maps were prepared for the study area and showed disastrous changes in the coastal landforms. It is a need that coastal communities worldwide must address the challenges of coastal flooding and rising sea levels caused by climate change. Climate change is causing uneven rainfall distribution, storms and cyclones, leading to coastal erosion, flooding and landform damage. Additionally, it has a negative impact on the geomorphic features of coastlines.

A palynological record of mangrove biogeography, coastal geomorphological change, and prehistoric human activities from Cedar Keys, Florida, U.S.A.

Under the continuous warming trend in the 21st century, mangroves are likely to migrate into more temperate regions in North and South America. However, the biogeography of different mangrove species is still unclear, especially near their latitudinal range limits in the two continents. This study utilizes palynological, geochemical, and sedimentological analyses to record changes in the coastal morphology and vegetation during the Holocene in Cedar Keys, Florida, the mangrove sub-range limit in North America. The multi-proxy dataset indicates that the milder winters during the Medieval Climate Anomaly likely facilitated the establishment of mangroves in the study region, where Avicennia, Laguncularia, and Rhizophora were established in the ~12th (790–850 cal yr BP), ~14th (580–660 cal yr BP), and ~ 16th century (440–460 cal yr BP), respectively. Thus, the Medieval Climate Anomaly likely triggered the poleward mangrove migration in North and South America synchronously. Moreover, the multi-proxy dataset also documents the obliteration of the Woodland Culture near Cedar Keys, where a once-thriving native civilization on Seahorse Key was driven out by the European colonizers, who settled on the mainland and Atsena Otie Key. Over time, the relict sites of the Woodland people on Seahorse Key were covered by mangroves and marsh vegetation since the ~16th century. Overall, our dataset suggests that industrial-era warming may have intensified the poleward mangrove expansion, although this trend had started earlier during the Medieval Climate Anomaly.

Hydrographic surveys as an art of delineating the impact of climate change on the coastal environment

Marine acoustic techniques are quite efficient in remote seabed classifications and hydrographic investigations by providing highly detailed information about broad areas of the seafloor and the subsurface layers in a short period of time. Climatic change is considered as the forcing factor for the eustatic sea-level-rise along the Mediterranean coast, leading to the large coastal inundation and the subsidence of the ancient maritime installations, these ancient sites can be used as indicators for the relative changes in sea-level through later times. Marine surveys were carried out to delineate the coastal geomorphological changes associated with sea level rises and natural hazards along some areas on the coast of Alexandria during the last two millennia. Hydrographic and seismic surveys were implemented in the study area by using a multi-beam echo-sounder, side scan sonar, and sub-bottom profiler, then the acoustic data were calibrated with dated core samples and ROV camera images. Multi-beam is considered the most commonly used tool in harbor surveys utilizing the returned acoustic signals to measure the depth of the seafloor, while the side scan sonar instrument provides high-resolution images for the elevated structures from the seafloor depending on the backscatter strength of the signal, and the sub-bottom profiler uses chirp waves that deliver high resolution vertical images for the subsurface sediment situation. Results of sonar imaging and bathymetric mapping outlined submerged margins of archaeological remains related to ancient Ptolemaic and Greek ports. Seismic interpretations revealed significant changes in the coastal geomorphology, where the massive burial of the port structure indicated the occurrence of sudden natural hazards originated from seismic waves; therefore, a destructive tsunami wave accompanied by sediment slumping that followed by eustatic sea-level-rise seems to be the dominant factors for this dramatic burial. The research results showed the potentiality of hydrographic surveys in detecting climate change indicators.

Occurrence mode of Holocene tsunami overwash controlled by the geomorphic development along the eastern Nankai Trough, central Japan

Re-analysis of the lithological, paleontological, and geochemical data of three lagoonal sediment cores reveal the tsunami overwash history from 8000 to 6500 cal BP along the northern Suruga Bay coast, facing the eastern Nankai Trough. The coring sites are located in a transcect 0.8, 1.5, and 1.7 km inland, respectively, from the coastline at the time the overwash events occurred. The washover sand beds are distinguished from the lagoonal muds by the presence of quartz and mica, which are abundant on the outer (marine) side of the lagoon, as well as marine shell fossils. The increased C/S ratio often associated with sand beds, reflects input of open seawater to the reductive lagoon, and supports this interpretation. A maximum of eight tsunami deposits were identified between ∼7800 and 6500 cal BP, many of which can be correlated between the three cores. The magnitude of tsunami overwash implied by the thickness and grain size of tsunami deposits, and increase of C/S ratio following their deposition is relatively large at ∼7500-7200 cal BP during the post-glacial sea level rise and decreases with time during the subsequent high sea level stand. This occurrence mode (timing and scale of formation) of tsunami washover is explained by temporal changes in coastal geomorphology, rather than differences in the magnitude of individual tsunamis. Around 7500-7200 cal BP, sea level rise equilibrated with or exceeded the growth of the bay mouth barrier, and tsunamis could easily cross the small barrier and enter the lagoon, leaving behind thick and coarse-grained deposits. As the barrier becomes larger during the subsequent sea-level highstand, only the highest-amplitude waves exceeded the height of the barrier. By ∼6500 years ago, the barrier was high enough to prevent tsunamis from entering the lagoon. Similarly, the occurrence mode of tsunami deposits reported along the coast of Suruga Bay and Enshu-nada over the past 6000 years can be explained in relation to the growth of coastal barriers.

Impacts of morphological change on coastal landscape dynamics in Monpura Island in the northern Bay of Bengal, Bangladesh

Coastal morphological change and landscape dynamics have been creating a new window for taking immediate sustainable management strategies for coastal resources management. The dynamic nature of coastal morphological response includes erosion/accretion of landmass, development of an island by sedimentation, movement of the island, and change in geometry and shape. The objectives of the study illustrate morphological change, driver, and mechanism of morphological change, and the effects of morphological change on coastal landscape dynamics. The study also explores spatio-temporal landscape dynamics effects on coastal ecosystem services and livelihood pattern of the coastal community. The novelty of the present research is that how morphological change influence in response to landscape dynamics and its ecosystem services by exploring historical data including shoreline change, century scale erosion and accretion, stability of the islands since 1776 to 2021. In this study, historical maps (i.e., Rennell’s map in 1776 and Tassin map in 1840), Topographic Survey map (1943) and remotely sensed digital image (i.e., Landsat TM in 1990, 2000 and 2010, and Landsat OLI in 2021) have been used to quantify coastal geomorphological change and landscape dynamics through RS and GIS tools and techniques. The finding of the study showed remarkable change occurred in geomorphology of the Monpura Island over the period of 245 years. The spatial coverage of the island has been declined dramatically, which is quantified ∼2905 ha from 1776 to 2021. In the century scale from 1840 to 1943, erosion is observed higher than accretion, and the statistics showing that 8963.40 ha eroded along the east flank of Island. In the northern flank of the Island, Net Shoreline Movement (NSM) and the rate of shoreline movement which expressed by EPR showed highest and flowed by ∼4 km and -126.55 m/y toward landmass. During the epoch 1990–2021, because of morphological change and anthropogenic interventions, the crop land of the Island has been significantly declined by ∼38%, while the rivers and settlement spatial coverage have been increased by ∼768% and ∼153%, with an annual rate of change ∼25% and ∼5% respectively. These outcomes and prepared maps of the current research will be supportive for the local inhabitant, coastal morphologist, and environmental resources management manager, national and international policy advisor, government and non-movement stakeholder, researcher to observe coastal morpho-dynamics including shoreline dynamics, coastal erosion and accretion and its impacts on landscape and ecosystem services.

Becoming Cholgueros: An archaeology of the 18th–20th centuries in the Chonos archipelago of Western Patagonia (Chile)

This article discusses the archaeological record of occupations associated with the extraction of coastal resources during the late 18th to early 20th centuries in the Chonos Archipelago (43°50’–46°50’S, Patagonia, South America). The characteristics of its occupation by Creole/European groups known as Cholgueros have not yet been archeologically addressed. Cholgueros occupations originated intensely over short periods of time and specialised in the extraction of primary coastal resources for the canned food industry. They are composed of large accumulations of unfragmented, uncompacted, and nonstratigraphic shells of a small number of species of mollusks of commercial value, such as Mytilus. Intertidal management areas are also recorded on these sites, such as stone corrals and boatyard or rock clearance areas to prevent boats from hitting intertidal stones. Due to the reduced time scale of formation of these sites they are sensitive to frequent coastal geomorphological changes and therefore sedimentary witnesses to regional coastal dynamics. The analysis of the Cholgueros sites’ evidence broadens our knowledge on coastal use in history, thus allowing us to understand the long timescale of human occupation of the area.

Application of geomorphological maps and LiDAR to volumetrically measure coastal geomorphological change from Hurricane Sandy at Fire Island National Seashore

The geomorphological map offers a snapshot of the landforms generated through topographical response to physical process drivers within a given landscape. A comparison of geomorphological maps with consistently and objectively identified landform boundaries allows for the assessment of spatiotemporal variations in process-response dynamics that represent the fundamental nature of geomorphological evolution, and form a basis to derive quantitative metrics of landform development. Two geomorphological maps of Fire Island National Seashore created from LiDAR datasets and orthophotography collected prior to and immediately following Hurricane Sandy were compared according to consistent and objective criteria. The mapped geomorphology and the LiDAR elevation data facilitated the use of regional-residual separation methods to assign sediment volumes to specific processes and landforms. This led to the calculation of sediment volumes deposited as beaches, foredunes, and washover deposits before and after the storm and to the quantification of the changes associated with the storm across the entire 50 km stretch of barrier coastline that comprises Fire Island. The temporal comparisons indicated that different portions of Fire Island exhibited variable geomorphological responses to a major storm. Notably, the central and western portion of the island, from 6 km to 36 km from the mouth of Fire Island Inlet, experienced substantial losses to coastal dunes — on the order of 2.9 × 106 m3 of sediment. The beaches in this segment of the coastline gained volume (~86,000 m3) in the storm indicating that the dunes provided a source of sediment to the beach, both buffering erosion and supplying sand to the littoral system. The eastern third of the island experienced beach erosion (~540,000 m3) and erosion of the dunes (~350,000 m3), as well as a significant amount of overwash deposition (~250,000 m3) that represents a transfer of sediment from the beach/dune reservoir to the backbarrier. This mode of geomorphological evolution adds elevation to the backbarrier at the expense of sediment available to buffer the shoreline position. Two 6 km strecthes of Fire Island coastline, Bellport/Old Inlet and Talisman/Watch Hill, exemplify the geomorphological response of the eastern and central potions of the island to the impact of Hurricane Sandy: 1) at Bellport/Old Inlet, overwash deposition was partially sourced from beach deposits adding elevation to the backbarrier at the expense of the shoreline position; and 2) at Talisman/Watch Hill, sediment stored in dune systems was transferred to the beach to slow storm induced shoreline retreat, and the dune buffer and its associated resilience was reduced.In quantifying the system response of a barrier island to a major storm event like Hurricane Sandy, we demonstrate the feasibility and utility of deriving metrics of geomorphological change from geomorphological maps. This approach of quantifying process-response outcomes through mapping is broadly applicable to a variety of geomorphological settings and timescales given a consistent means of boundary determination and using regional-residual separation.

ADVANCES IN THE APPLICATION OF DIGITAL ELEVATION MODELS (DEMS) FOR THE EVALUATION OF COASTAL FLOODING

Abstract Meteoceanographic forces act daily, provoking rapid changes in coastal geomorphology and impacting the human infrastructure located near the sea, principally on low-lying coasts. The current ongoing rise in sea level provoked by climate change is also a major source of concern for local and regional authorities. Geospatial models of coastal flooding are evolving rapidly, together with geomorphometric tools and their applications. These initiatives may permit the implementation of medium-and long term actions to minimize the effects of flooding, although a range of methodological considerations must be taken into account. Digital Elevation Models (DEMs) have become increasingly more accurate due to the integration of altimetric references and vertical data, as well as the increasing quality of the sensors used. For example, the application of the bathtub approach to coastal flooding assessment has been relatively successful. The choice of the flood model should include the careful selection of methods that ensure the most adequate application of the model.

Monitoring of Coastal Geomorphological Changes in Wolchun Beach after LNG Base Construction

Kim, I.H.; Kim, J.H.; Nam, J.M.; Lee, H.S., and Song, D.S., 2019. Monitoring of coastal geomorphological changes in Wolchun Beach after LNG base construction. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 366-370. Coconut Creek (Florida), ISSN 0749-0208.Constructions of industrial facilities nearby coastal region often break a natural equilibrium between sediment budget and littoral current condition. The Wolchun beach, which is facing East Sea of South Korea, had a longshore stretch of 1.9 km before the LNG storing base was constructed. In this study, we analyzed the change patterns of the Wolchun beach topography caused by the installation of artificial structures, as well as coastal geomorphological changes. The control points in the study area were divided into 8 sections, each spaced 50 m pitch apart, for the trend analysis of the beach profiles. Also, the sea zone with 1.35 km2 area was divided into 6 sections with 300 m × 750 m per section, for the monitoring of water depth variation. The surveying results show that the area of the northern side of the Wolchun beach near the LNG storage base was continuously increased due to the accumulation of sediment after the construction of LNG base. On the contrary, the continuous erosion occurred on the south side of Wolchun beach, and it was observed that the water depth near the surf zone is deepened. Also, the bathymetric change of the test area was occurred actively, and the significantly unstable change of water depth in the region of about -10 m ∼ -15 m was confirmed to be generated by the breakwater with the disrupting of operable wave condition. It is found that the natural equilibrium has been collapsed along the unexpectedly formed shielding zone after the construction of the LNG base and the breakwater on the outside of the base.

Latitudinal gradient in intertidal seaweed composition off the coast of southern Brazil and Uruguay

Seaweed latitudinal patterns of diversity present singularities, with implications for ecological, biogeographic and conservation studies. Despite observed global trends, distinct gradients of marine biodiversity occur along the Southwestern Atlantic (SWA) coast. However, the transitional warm-temperate marine province is a major knowledge gap, limiting conclusions about regional seaweed biodiversity. Our study investigated the composition of macroalgal assemblages in rocky intertidal shores between southern Brazil and Uruguay (from 26 °S to 35 °S), accounting for the regional oceanography and coastline features. Integrating historical and new data, we found a significant latitudinal gradient in seaweed species richness and turnover. The complex thermo-haline structure of the coastal waters, summed to large local fluvial discharges (i.e., La Plata River and Patos-Mirim Lagoon), significantly impacted the distributional pattern of macroalgal assemblages. Sea surface temperature and salinity are the main drivers of the species composition and distribution, despite the changes in coastal geomorphology and substrate availability. Whilst the northernmost section (26 °S–29 °S) was characterized by a tropical/warm-temperate phycoflora, the southernmost (32 °S–35 °S) was dominated by eurythermic and euryhaline species. Taking into account this and previous phycogeographic studies, the lowest seaweed species richness seen in SWA rocky shores occurs across 32 °S and 37 °S, while increasing towards both north (into the tropical marine province) and south (into the cold-temperate marine province). Our study fulfills knowledge gaps in Southwestern Atlantic Ocean biogeography, providing baseline information for conservation efforts and for the detection of ongoing human impacts on intertidal macroalgal assemblages.

Temporal and spatial variability in coastline response to declining sea-ice in northwest Alaska

Arctic sea-ice is declining in extent, leaving coastlines exposed to more storm-wave events. There is an urgent need to understand how these changes affect geomorphic processes along Arctic coasts. Here we describe spatial and temporal patterns of shoreline changes along two geomorphologically distinct, storm-wave dominated reaches of the Chukchi Sea coastline over the last 64 years. One study area encompasses the west- to southwest-facing, coarse-clastic shoreline and ice-rich bluffs of Cape Krusenstern (CAKR). The other covers the north-facing, sandy shorelines on barrier islands, ice-rich bluffs, and the Cape Espenberg spit in the Bering Land Bridge National Park (BELA). Both study areas lie within the zone of continuous permafrost, which exists both on and offshore and outcrops as ice-rich bluffs along the BELA coast. We mapped changes in coastal geomorphology over three observation periods: 1950–1980, 1980–2003, and 2003–2014 using aerial and satellite imagery. We then compared these geomorphic changes to changes in sea-ice coverage, which declined ~10 days per decade between 1979 and 2016 in the southern Chukchi Sea. Changes in coastal geomorphology in both BELA and CAKR exhibited high spatial variability over the study period. Between 2003 and 2014, shorelines of barrier islands in BELA exhibited the highest mean rates of change, −1.5 m yr−1, while coarse, clastic barrier beaches in CAKR showed only minimal change. Overall, shorelines in both BELA and CAKR became more dynamic (increasing erosion or increasing accumulation) after ca. 2003, with spatial variability in shoreline changes roughly doubling between the first period of observation (1950–1980) and the last (2003–2014). This increase in coastal dynamism may signal a transitional period leading to new state of geomorphic equilibria along these ice-affected coastlines.

The beach slopes and grain size distribution at Anoi Itam and Pasir Putih Beaches, Sabang City

Since ocean and land greatly influence on coastal processes, and continually affected by these dynamics, the coastal zone become the most dynamical region of the ocean. Coastal geomorphological changes principally in a more specific of beach processes and made of are found from the characteristics of the sediments over certain coastal waters. This research examines the relationship between beach slope and mean grain size. The objective of the research is to explain the mechanisms of sediment distribution associated with different beach slopes. The sampling locations were situated at Anoi Itam and Pasir Putih Beaches of Sabang City on October 2016 and April 2017. Coring method was used in this research. There were six collection sites with two repetitions of treatment in each location. The distribution of sediment based on grain size was measured using wet sieving procedure extracted by stratified sieving. The results showed that medium sand are dominant at Anoi Itam and Pasir Putih Beaches while beach slopes vary from nearly flat to gently sloping.

Implicaciones sedimentológicas sobre el cambio en la cobertura del bosque de manglar en Boca Zacate, Humedal Nacional Térraba-Sierpe, Costa Rica

In the last sixty years many geomorphological changes have occurred in Costa Rica's Térraba-Sierpe National Wetlands. Changes in coastal geomorphology are generally associated with erosion or accretion of sediment, which has led to the removal of sections of mangrove forests or sediment banks colonized by mangroves. The aim of this study was to analyze sedimentation as a leading process in the dynamics of coastal morphology and its implications for mangrove forest cover in the Boca Zacate area of Térraba-Sierpe wetlands. The study was conducted in the sectors of Bocón, Brujo and Coco Island in Boca Zacate, from 2008 to 2013. The research was based on a multi-temporal analysis of coastal morphology using aerial photographs from the years 1948, 1960, 1974, 1978, 1984, 1992 and 2011. The following measurements were also performed: monthly sedimentation rate (g/cm2/day), and granulometric composition and content of chemical elements in the sediments of the study area. These last two measurements were performed once each in the dry and rainy seasons during the years of study. The results indicated that over the past 60 years, Boca Zacate has witnessed a process of sustained erosion; from 1948 through 2001, losing 10.6 % of its land and approximately 8.9 % of its forest cover. It has also experienced accretion in the area of Coco Island. The Brujo sector showed the highest sedimentation rate and the Camibar estuary, the lowest. The dominant type of sediment in all study sites was sand, followed by clay and silt. The most widespread chemical elements (mg/L) included magnesium, calcium and potassium; others, such as manganese, iron, aluminum, phosphorus, zinc and copper, were measured in smaller amounts. Transport, composition and quantity of sediment in Boca Zacate are crucial to the changes that have occurred on the coastal area of La Boca, where the presence of dead trees was evident. This geomorphological analysis holds great importance for future guidelines and actions for the conservation and integrated management of the mangrove in Térraba-Sierpe National Wetlands.

Past, Present and Future Perspectives of Sediment Compaction as a Driver of Relative Sea Level and Coastal Change

Compaction describes a range of natural syn- and post-depositional processes that reduce the volume of sediments deposited in low-lying coastal areas, causing land-level lowering and a distortion of stratigraphic sequences. Compaction affects our reconstructions and understanding of historic sea levels, influences how relative sea level changes in the future and can act as a catalyst for rapid, widespread changes in coastal geomorphology. Rates of compaction-induced relative sea-level rise vary across space and through time in response to a range of natural and anthropogenically accelerated processes and conditions. This paper provides a summary of our understanding of the causes and effects of compaction, considering findings from key palaeoenvironmental and stratigraphic studies, sea-level reconstructions and recent observational data. It then considers the implications of these findings for our ability to project compaction-induced relative sea-level and associated coastal changes into the future.

Post-earthquake coastal evolution and recovery of an embayed beach in central-southern Chile

Earthquakes and tsunamis are significant factors for change along active margin shores, and influence coastal evolution. The Chilean coast was affected in 2010 by a subduction earthquake with a magnitude of Mw8.8 and also by a trans-Pacific tsunami, which generated violent geomorphologic changes and damaged homes. Following these events, the magnitude of the changes which affect Chile's central-southern coast (37°S) and the role of subduction earthquakes in coastal evolution on a historical scale were investigated.At Lebu bay (an embayed beach) data were generated for variations in time and space along the shoreline, topographical and bathymetric changes in the bay, and for morphodynamic littoral processes. Logarithmic and parabolic models were applied to the shoreline along with map overlays in order to determine changes. The shoreline processes were analyzed based on statistics for waves, tides and sediment transport for pre- and post-tsunami conditions.An average accretion rate of 2.80m/year (1984–2010) was established for the shoreline, with a strong trend towards accretion in the last 30years. A parabolic function best represented the general form of the shoreline, although the presence of a river in the concave zone affected the fit in this sector. Two factors controlled historical changes on the beach: one of anthropic origin in addition to the earthquake and tsunami on February 27th, 2010. The post-earthquake recovery was fast, and currently the beach is in a stable condition despite the inter-seismic subsidence process previous to the event. This coastal system showed a high resilience in the face of coastal geomorphological changes induced by high-impact natural disturbances. However, the opposite occurred in relation to changes induced by anthropogenic disturbances.

Geotemporal vectors of coastal geomorphological change interacting with National Park Service management policy at Great Kills Park, Gateway National Recreation Area, USA

The trend and episodes of erosion at Great Kills Park, part of the National Park Service, are products of the origin of the park's location and the impact of a negative sediment budget. Management response to the impacts of erosion is somewhat limited by National Park Service philosophy, but some options remain because the negative sediment budget is a product of barriers to sediment transport updrift of the Park. The erosional situation is exacerbated by an exposure of an antecedent backmarsh feature within the Park that is affecting the inshore pattern of incident waves. Recent monitoring data indicate planform conformity to an updrift log-spiral erosional bluff that extends downdrift to a site with beach and dune features. Despite a general net negative sediment budget in the profile, the dune feature is increasing in volume as it shifts inland, fitting models of foredune development. Seasonal monitoring of the topography records that storms cause a stepwise inland displacement of an updrift portion of the Park and a more linear displacement in the downdrift portion. Among the options consistent with management policy responding to the negative sediment budget issue is an opportunity to work within the scale of the small sediment transport cell and backpass sediment toward the updrift margin of the cell.

Strategic Science: New Frameworks To Bring Scientific Expertise To Environmental Disaster Response

Strategic Science: New Frameworks To Bring Scientific Expertise To Environmental Disaster Response