High Accretion Research Articles

Geo-environmental monitoring of coastal and land resources for Coatzacoalcos coastal region

Coatzacoalcos is one of the notable Mexico coastal areas regarding location, activities, and resources. The purpose of the current study is to use geographic techniques to assess the spatial and temporal changes in Land Use/Cover (LULC), Land Surface Temperature (LST), and Shoreline as a result of anthropogenic and natural factors. Four calibrated multi-temporal Landsat images, dated 1993, 2003, 2013, and 2023, were combined and processed to accomplish this goal. The six primary LULC classes forest, built-up land, mining, water bodies, and agriculture were mapped using RF Machine learning algorithms. The last period (2003–2023) shows the highest rate of built-up land expansion, while the years 1993–2013 show the lowest rate of agricultural land reduction. Forest cover in the southeast decreased steadily from 339.25, 308.49, 287.43, and 211.83 km2 in 1993, 2003, 2013, and 2023. There is a slight difference in mean LST between built-up areas that recorded 26, 29, 32, and 33 °C in 1993, 2003, 2013, and 2023, respectively. The following is an order of LULC from lowest to highest LST during 2023 water body 12 °C, Forest 19 °C, Agriculture Land 22 °C, Mining 26 °C, Barren Land 34 °C and Built-up Land 33 °C. In Zone B near Coatzacoalcos showed particularly high accretion as a result of building artificial structures. Maximum rates of accretion and erosion were recorded at 2.0 m/year and −9.63 m/year, respectively. Fortunately, Zone C has minimal urban development and is home to forests and agricultural areas, so the potential negative effects are reduced. This study aids in understanding spatial and temporal LULC changes, LST variations, and shoreline dynamics, crucial for the sustainable management of Coatzacoalcos coastal resources in Mexico.

SPATIO-TEMPORAL SCALES OF LAND COVER AND SHORELINE DYNAMICS IN BANAYBANAY, DAVAO ORIENTAL, PHILIPPINES USING AVAILABLE OPTICAL SATELLITE IMAGERY

Abstract. Shoreline dynamics are often the most visible indicators of changes that occur in coastal areas. It is essential to consider a shoreline's physical location while evaluating changes on a temporal and chronological scale. The shoreline in Banaybanay, Davao Oriental, has undergone significant land use changes, leading to negative impacts on related coastal processes, including mariculture conditions in the area. This study aims to determine changes in land cover and shoreline in Banaybanay’s coastal barangays by analyzing satellite images from 1989–2021 using remote sensing, GIS, and Digital Shoreline Analysis Systems (DSAS). The study found that rapid land cover changes in the area were primarily driven by development growth, urbanization, mining, and human activities. The Net Shoreline Movement (NSM), End Point Rate (EPR), and Linear Regression Rate (LRR) results indicated accretion in Banaybanay’s coastal areas, corresponding to an increase in built-ups and barren from 1989–2021. Characterization of land cover and shoreline change revealed high erosion associated with land cover change of barren-water and grassland/brushland-water with a maximum erosion value of −1.19 m/yr. Conversely, very high accretion was mainly characterized by land cover change of water-built-up, barren-built-up, and water-barren with a maximum accretion value of 9.58 m/yr.

Deltaic marsh accretion under episodic sediment supply controlled by river regulations and storms: Implications for coastal wetlands restoration in the Yellow River Delta

Sediment supply has long been recognized as a critical factor affecting salt marsh evolutions. Subject to fluctuating river discharges and coastal hydrodynamics, sediment supply to deltaic marshes are episodic rather than continuous. To evaluate the impacts of episodic sediment delivery under river regulations and storm events on deltaic marsh accretion, a 5-month (April 18th to September 4th, 2021) field campaign was conducted at a Spartina alterniflora marsh of the Yellow River Delta, China. Nine storm events and the Water-Sediment Regulation Scheme (WSRS) coinciding with a freshwater diversion were captured. It was found that the two phases of the WSRS differed greatly in their contribution to marsh accretion. During the Water-Regulation Phase (WRP), marsh accretion rates showed little difference with pre-WRP periods. However, the subsequent Sediment-Regulation Phase (SRP) contributed to ∼15 % of annual accretion within only 4 days, suggesting the SRP was more effective in nourishing deltaic marshes with sediment. Further analyses indicated that the higher accretion during SRP was attributed to both higher sediment concentrations and more favorable sediment pathways, influenced by delta-scale river-tide interactions. Observations also showed that storm events contributed to half of the marsh accretion during the non-WSRS period when the fluvial sediment supply was very low. During storms, wave-induced intertidal resuspension acted as the major sediment sources. Under favorable conditions (onshore wind, high water levels, high waves), tidal-averaged sediment delivery to marshes underwent as much as fifty-fold increase compared with the calm period. The observed marsh dynamics suggested that marsh sedimentations depended on not only the seaward sediment concentrations, but also the sediment transport pathways. For deltaic marsh restoration practices, we proposed that marsh-orientated schemes which align river regulations with favorable meteorological and hydrodynamic conditions, could potentially make better use of fluvial sediment for deltaic marsh nourishment.

Assessing the Impact of Coastal Erosion on Land use and Landcover, A Time Series Analysis using DSAS and GIS in Cuddalore Shore, Tamil Nadu, India

Abstract One of the most fragile places on earth is the coastal zone. There are several different ecosystems in this area. In this area, erosion and accretion are typical natural occurrences. These changes could also threaten the coastal ecology. Uneven coastal changes can result from natural processes such rainfall, cyclones, floods, tectonic shifts and longshore drift. Similar to this, anthropogenic influences like mining, unscientific land use, urbanisation, etc., contribute to coastal processes and bring much more significant alterations in the coastal region. Therefore, identifying such a location is crucial. Advanced approaches for studying shoreline change have been made possible by geospatial technology. The enormous effort to obtain an accurate result over a greater area has become easier as a result. In order to examine the changes in the Cuddalore shoreline during the years 2002, 2007, 2013, 2017, and 2022, Landsat satellite imageries with 30 m spatial resolution were used. The Digital Shoreline Analysis System (DSAS) tool for analysing shoreline change has been integrated to Geographic Information System (GIS) software. DSAS was used to construct the baseline transects for the shoreline change measurement. Using the MATLAB feature runtime function for ArcGIS, the rate of shoreline change was computed. Based on the DSAS output, the area of high erosion, low erosion, stable, and low accretion, high accretion zones were assessed on the coastline. The results reveal that 15.38% of the shoreline, around 6.8 km is under high erosion. 12.2% of the shoreline, which is around 5.4 km, is under low erosion. 32% of the shoreline, around 14.5 km, is a stable region. 26.9% of shorelines, around 11.9 km, is low accretion, and 12.6% of shorelines, around 5.6 km, is high accretion. The coastal villages, namely, Gundupallavadi, Cuddalore, Thandavarayancholanga pettai, Ariyakoshti and parangipettai have a high erosion with a maximum rate of change between -3 to -14 m/y. The coastal villages Patchayankuppam, Cuddalore, Tiruchchepuram, Kayalpattu, Kothattai, Ariyakoshti, Parangipettai have high accretion with a maximum rate of change between 3 to 10 m/y.

Shoreline Change Assessment in the Orashi River, Rivers State, Nigeria, using the Digital Shoreline Analysis System (DSAS)

Shoreline change profoundly impacts coastal geology and coastal communities. This study, spanning three decades from 1992 to 2022, employed the Digital Shoreline Analysis System (DSAS) to assess the Orashi River shoreline dynamics in Nigeria. Using Landsat imagery data from the United States Geological Survey (USGS) and ArcGIS 10.6, DSAS 5.0 software was utilized for analysis. Various statistical methods, including Linear Regression Rate (LRR), Weighted Linear Regression (WLR), End Point Rate (EPR), Net Shoreline Movement (NSM), and Shoreline Change Envelope (SCE), quantified shoreline changes. The findings consistently reveal significant shoreline regression. LRR, -1.78 to -1.07, highlights continuous landward movement, signifying erosion’s persistent impact. WLR rates reaffirm this trend, closely mirroring the range of -1.78 to -1.07. EPR, -2.79 to -1.29, further underline the erosional trend, emphasizing substantial inland shifts. NSM, ranging from -48.66 to -20.30, signifies substantial shoreline retreat, showcasing erosion’s profound effect. The NSM, varying from 0.69 to -11.50, illustrates dynamic shoreline movement with varying degrees of erosion. The outcomes identify prevalent erosion, particularly in Very High Erosion (VHE) areas, while High Accretion (HA) and Very High Accretion (VHA) zones experience shoreline gain. These classifications inform coastal management strategies, urging protective measures for VHE areas and development opportunities in HA and VHA zones. The variability in shoreline change underscores coastal dynamics’ complexity. This study contributes to understanding the Orashi River’s shoreline processes, guiding sustainable coastal management and environmental conservation efforts. Continued monitoring and research are crucial for adapting to the evolving coastal landscape’s impact on the environment and local communities.

From the headwaters to the sea: The role of riparian, alluvial, and tidal wetlands to filter nutrients and ameliorate eutrophication

AbstractWetlands are known for their ability to trap sediment and eliminate pollutants from the surrounding catchment. However, less is known regarding the differential role of headwater, mid‐catchment, and coastal wetlands in filtering these materials. Soil accretion, organic carbon (C), total nitrogen (N), and total phosphorus (P) were measured in wetlands from the headwaters to the mouth of the Altamaha River, Georgia, USA to assess how sediment deposition, C sequestration, and N and P burial vary along the waterway. Soil cores (n = 2 per site) were collected from riparian, upper and lower alluvial, tidal freshwater forest and marsh, brackish marsh, and salt marsh. Two‐centimeter depth increments were analyzed for 137Cs, to determine soil accretion, bulk density, and C, N, and P concentration. Accretion exhibited a bimodel distribution with the highest rates in riparian wetlands of the headwaters (3.9 mm/year) and in tidal fresh and brackish marshes (4.7–5.4 mm/year) of the estuary. Accretion rates were considerably lower in alluvial and tidal fresh forests and salt marshes (0.9–2.5 mm/year). Carbon sequestration and N burial followed a similar trend with the greatest accumulation in soils of tidal fresh and brackish marshes (102–150 g C/m2/year, 7.1–9.5 g N/m2/year) that had not only high accretion but also high organic matter content (11%–12% C). Riparian soils with their low C content, high bulk density, and high P content had much greater sediment deposition (3310 g/m2/year) and P burial (2.75 g P/m2/year) than other wetlands along the waterway (180–1730 g sediment/m2/year, 0.23–0.90 g P/m2/year). Results suggest that, in the Altamaha River, sediment deposition and P removal are maximized in the headwaters thereby protecting downstream freshwaters from the effects of P eutrophication. Tidal fresh and brackish marshes with their high rates of N burial can aid in protecting estuaries from N enrichment, many of which suffer from the effects of N eutrophication. Results from this study are scalable to other rivers of the southeastern U.S. piedmont and coastal plain and similar rivers of this size, topography, and geology.

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

<h2 align="left"><span style="font-size: 10px;"><br /></span></h2><p><span style="font-size: 10px;">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. </span></p>

Application of Geospatial Techniques to Determine Coastal Erosion and Accretion along the Ramanathapuram Shore, Tamil Nadu, India

Abstract The coastal region is one of the most sensitive areas on earth. This region has a diversified ecosystem. Erosion and accretion are common natural phenomena that can be seen in this region. In some circumstances, these changes become hazardous to the coastal ecosystem. Natural processes such as rainfall, flood, cyclone, longshore drift, and tectonic shifts can trigger irregular coastal changes. Similarly, anthropogenic factors such as urbanization, unscientific land usage, mining, etc., enhance coastal dynamics and make larger changes. Hence identification of such region has great importance. Geospatial technology has brought various advanced methods for shoreline change studies. It has decreased the huge effort for getting an accurate result for a larger area. Landsat satellite imageries with 30 m spatial resolution have been used for studying the changes in the shoreline of Ramanathapuram for the years 2000, 2005, 2010, 2015 and 2020. In Geographic Information System (GIS) software, the Digital Shoreline Analysis System (DSAS) tool is added for shoreline change analysis. DSAS will build the baseline transects. The rate of shoreline change was calculated using the MATLAB feature runtime function for ArcGIS. Based on the DSAS output, the region of high erosion, low erosion, stable, and low accretion, high accretion zones have been identified on the shore. The results reveal that 5.1% of the shoreline, around 9.3 km is under high erosion, 11.5% of the shoreline, which is around 20.8 km, is under low erosion, 71% of the shoreline, around 128 km, is a stable region, 6.7% of shorelines, around 12 km, have low accretion, and 5.6% of shorelines, around 10.1 km, have high accretion. The coastal villages, namely, Mayakulam, Keelakakrai, Periapattinam, Mandapam, West-Pamban, and East-Rameswaram, have a high erosion with a maximum rate of change between 2.29 to 5.11 m/y. The coastal villages Ervadi, Kalimankund, Sattankonvalsai, South-Pamban and South-Rameswaram have high accretion with a maximum rate of change between 2.34 to 5.24 m/y.

Spit Evolution and Shoreline Changes Along Manamelkudi Coast Using Geo-Spatial Techniques and Statistical Approach

The historical shoreline changes from 1980 to 2020 along the Manamelkudi coast is studied using toposheet, satellite time-series Landsat data, and observed data. An attempt is made to recognise possible factors which are responsible for shoreline changes and spit growth at south Manamelkudi coast (Palk Strait), Eastern part of Pudukkottai district, Tamilnadu. During 1980–2020, the regions showed distinct spatio-temporal variability, which is discussed in relation to spit evolution and shoreline changes. The study also generated a long-term (1980-2020) shoreline change statistics (EPR, LRR, SCE and NSM, WLR) using the Digital Shoreline Analysis System (DSAS) at every 150 m interval for the Manamelkudi coast covering 42 km, identified the erosion and accretion and divide the shoreline into different classes of erosion and accretion. Identified lengths of shoreline with high erosion, low erosion, stable, low accretion and high accretion are, respectively, based on LRR. The results indicate that spit evolution is predominant along the Manamelkudi coast, with the highest percentage of erosion and accretion.

Analysis of Shoreline Changes in Ikoli River in Niger Delta Region Yenagoa, Bayelsa State Using Digital Shoreline Analysis System (DSAS)

The use of Digital Shoreline Analysis System was used to determine shoreline changes in Ikoli River, Yenagoa, Bayelsa State. Shoreline data were extracted from satellite imagery over thirty years (1991-2021). The basis of this study is to use Digital Shoreline Analysis System to determine erosion and accretion areas. The result reveals that the average erosion rate in the study area is 1.16 m/year and the accretion rate is 1.62 m/year along the Ikoli River in Ogbogoro Community in Yenagoa, Bayelsa State. The mean shoreline length is 5.24 km with a baseline length of 5.2 km and the area is classified into four zones to delineate properly area of erosion and accretion based on the five class of Linear regression rate, endpoint rate and weighted linear rate of which zone I contain very high erosion and high erosion with an area of landmass 255449.93 m2 of 38%, zone II contain moderate accretion, very high accretion and high accretion with a land area of 1666816.46 m2 with 24%, zone III has very high erosion and high erosion with an area of landmass 241610.85 m2 of 34 % and zone IV contain moderate accretion and high accretion with land area 30888.08 m2 with 4%. Out of the four zones, zone I and II were found to be eroding with 72% and zone II and IV contain accretion with 28%. The result shows that 44% of the area have been eroded. Therefore, coastal engineers, planners, and shoreline zone management authorities can use DSAS to create more appropriate management plans and regulations for coastal zones and other coastal parts of the state with similar geographic features.

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Detection of a Dense SiO Jet in the Evolved Protostellar Phase

Abstract Jets and outflows trace the accretion history of protostars. High-velocity molecular jets have been observed from several protostars in the early Class 0 phase of star formation, detected with the high-density tracer SiO. Until now, no clear jet has been detected with SiO emission from isolated evolved Class I protostellar systems. We report a prominent dense SiO jet from a Class I source G205S3 (HOPS-315: T bol ∼ 180 K, spectral index ∼0.417), with a moderately high mass-loss rate (∼0.59 × 10−6 M ⊙ yr−1) estimated from CO emission. Together, these features suggest that G205S3 is still in a high-accretion phase, similar to that expected of Class 0 objects. We compare G205S3 to a representative Class 0 system G206W2 (HOPS-399) and literature Class 0/I sources to explore the possible explanations behind the SiO emission seen at the later phase. We estimate a high inclination angle (∼40°) for G205S3 from CO emission, which may expose the infrared emission from the central core and mislead the spectral classification. However, the compact 1.3 mm continuum, C18O emission, location in the bolometric luminosity to submillimeter fluxes diagram, outflow force (∼3.26 × 10−5 M ⊙ km s−1 yr−1) are also analogous to that of Class I systems. We thus consider G205S3 to be at the very early phase of Class I, and in the late phase of high accretion. The episodic ejection could be due to the presence of an unknown binary, a planetary companion, or dense clumps, where the required mass for such high accretion could be supplied by a massive circumbinary disk.

Wind-luminosity evolution in NLS1 AGN 1H 0707−495

ABSTRACT Ultrafast outflows (UFOs) have been detected in the high-quality X-ray spectra of a number of active galactic nuclei (AGNs) with fairly high accretion rates and are thought to significantly contribute to the AGN feedback. After a decade of dedicated study, their launching mechanisms and structure are still not well understood, but variability techniques may provide useful constraints. In this work therefore we perform a flux-resolved X-ray spectroscopy on a highly accreting and variable NLS1 AGN, 1H 0707−495, using all archival XMM–Newton observations to study the structure of the UFO. We find that the wind spectral lines weaken at higher luminosities, most likely due to an increasing ionization parameter as previously found in a few similar sources. Instead, the velocity is anticorrelated with the luminosity, which is opposite to the trend observed in the NLS1 IRAS 13224−3809. Furthermore, the detection of the emission lines, which are not observed in IRAS 13224−3809, indicates a wind with a larger opening angle in 1H 0707−495, presumably due to a higher accretion rate. The emitting gas is found to remain broadly constant with the luminosity. We describe the variability of the wind with a scenario where the strong radiation extends the launch radius outwards and shields the outer emitting gas, similarly to super-Eddington compact objects, although other possible explanations are discussed. Our work provides several hints for a multiphase outflow in 1H 0707−495.

Spatio-Temporal Analysis of Shoreline Movements along the Coastal Stretch from Bortianor to Winneba, Ghana

Shoreline movement is largely dependent on the extent of erosion and accretion, thus making it one of the most dynamic geomorphic phenomena along the coast. The study sought to assess the spatio-temporal dynamics of shoreline movements along the coastal stretch between Bortianor in the Greater Accra Region and Winneba in the Central Region of Ghana from 2000 to 2020. The study used shoreline data mapped from field-based high resolution aerial imagery and Landsat 7 and 8 images. Digital Shoreline Analysis System (DSAS) software 5 was used for the data processing and analysis, with reference to Shoreline Change Envelope, Net Shoreline Movement, End Point Rate, Linear Regression Rate and Weighted Linear Regression. It was observed that the entire shoreline under study generally experienced a continuous retreat than advancement due to the moderate to very high accretion. This notwithstanding, very high erosion was observed on the eastern side of the coast in Fete, leading to an advancement of the shoreline. The study recommends constant monitoring of the coastline by researchers and relevant stakeholders and also the need to put in place protective mechanisms such as sea defenses by the Ministry of Water Resources, Works and Housing to avoid the worse scenarios being experienced in other parts of the Ghanaian coastline. Keywords: shoreline movements, accretion, erosion, shoreline retreat, shoreline advancement DOI: 10.7176/JEES/11-1-04 Publication date: January 31 st 2021

Changing-look active galactic nuclei: close binaries of supermassive black holes in action

Changing-look active galactic nuclei (CL-AGNs) as a new subpopulation challenge some fundamental physics of AGNs because the timescales of the phenomenon can hardly be reconciled with accretion disk models. In this Letter, we demonstrate the extreme case: close binaries of supermassive black holes (CB-SMBHs) with high eccentricities are able to trigger the CL transition through one orbit. In this scenario, binary black holes build up their own mini-disks by peeling gas off the inner edges of the circumbinary disk during the apastron phase, after which they tidally interact with the disks during the periastron phase to efficiently exchange angular momentum within one orbital period. For mini-disks rotating retrograde to the orbit, the tidal torque rapidly squeezes the tidal parts of the mini-disks into a much smaller radius, which rapidly results in higher accretion and short flares before the disks decline into type-2 AGNs. Prograde-rotation mini-disks gain angular momentum from the binary and rotate outward, which causes a rapid turn-off from type-1 to type-2. Turn-on occurs around the apastron phase. CB-SMBHs control cycle transitions between type-1 and type-2 with orbital periods but allow diverse properties in CL-AGN light curves.

Probing episodic accretion with chemistry: CALYPSO observations of the very-low-luminosity Class 0 protostar IRAM 04191+1522

Context. The process of mass accretion in the earliest phases of star formation is still not fully understood: does the accretion rate smoothly decline with the age of the protostar or are there short, intermittent accretion bursts? The latter option would also yield the possibility for very low-luminosity objects (VeLLOs) to be precursors of solar-type stars, even though they do not seem to have sufficiently high accretion rates to reach stellar masses during their protostellar lifetime. Nevertheless, probing such intermittent events in the deeply embedded phase is not easy. Chemical signatures in the protostellar envelope can trace a past accretion burst. Aims. We aim to explore whether or not the observed C18O and N2H+ emission pattern towards the VeLLO IRAM 04191+1522 can be understood in the framework of a scenario where the emission is chemically tracing a past accretion burst. Methods. We used high-angular-resolution Plateau de Bure Interferometer (PdBI) observations of C18O and N2H+ towards IRAM 04191+1522 that were obtained as part of the CALYPSO IRAM Large Program (Continuum And Lines in Young ProtoStellar Objects). We model these observations using a chemical code with a time-dependent physical structure coupled with a radiative transfer module, where we allow for variations in the source luminosity. Results. We find that the N2H+ line emission shows a central hole, with the N2H+ emission peaking at a radius of about 10′′ (1400 au) from the source, while the C18O emission is compact (1.3′′ FWHM, corresponding to 182 au). The morphology of these two lines cannot be reproduced with a constant luminosity model based on the present-day internal luminosity (0.08 L⊙). However, the N2H+ peaks are consistent with a constant-luminosity model of 12 L⊙. Using a model with time-dependent temperature and density profiles, we show that the observed N2H+ peak emission could indeed be caused by a past accretion burst with a luminosity 150 times higher than the present-day luminosity. Such a burst should have occurred a couple of hundred years ago. Conclusions. We suggest that an accretion burst occurred in IRAM 04191+1522 in the recent past. If such bursts are common and sufficiently long in VeLLOs, they could lead to higher accretion onto the central object than their luminosity suggests. For IRAM 04191 in particular, our results yield an estimated final mass of 0.2–0.25 M⊙ by the end of the Class 0 phase, which would make this object a low-mass star rather than a brown dwarf. More generally, our analysis demonstrates that the combination of observations of N2H+ and C18O is a more reliable diagnostic of past outburst activity than C18O or N2H+ emission alone.

Shoreline Evolution Between Al Lith and Ras Mahāsin on the Red Sea Coast, Saudi Arabia Using GIS and DSAS Techniques

A large proportion of the world's population lives in coastal areas. These zones play a vital role in the socioeconomic aspects of coastal communities. The evolution of shoreline along the zones is of great importance to scientists, and engineers as well as coastal management. This research aims to assess and understand the dynamics of shoreline along the Red Sea coast between Al Lith and Ras Mahāsin, using medium-resolution satellite imagery over 34 years (1984–2018) as well as to predict futuristic changes in the shoreline position until 2038. The tasseled cap transformation tools in ArcGIS 10.2 are used to extract shoreline position for seventh intervals time. These shorelines are analyzed by the digital shoreline analysis system in four statistical functions, namely (EPR, LRR, NSM, and LMS). The endpoint rate is used to predict futuristic shoreline positions. The results reveal that the evolutions of shoreline in the form of erosion and accretion patterns, as surface area exceed 12.3 and 0.89 km2, respectively. The evolution rates were classified based on LRR into five classes: [i.e., − 11.84 to − 7.85 (very high erosion), − 7.85 to − 4.17 (moderate erosion), − 4.17 to 0.00 (low erosion), 0.00 to 1.28 (low accretion), and 1.280 to 14.44 (high accretion)]. These changes are attributed to the impact of the extreme wave action and the littoral drifts of sediments by longshore currents. The prediction model reveals that a large portion of the coastal zone is vulnerable to a high rate of shoreline disintegration.

Shoreline Change Dynamics using Digital Shoreline Analysis in Cemara Besar Island

This paper will describe a study to find out the shoreline changes that occurred on Cemara Besar Island along with the accretion and abrasion. Data taken from the images was obtained through google earth as a result of radiometry and geometry correction from Landsat satellites in the last 5 years. Wind data is obtained from ecmwf interm every season for 5 years. Analysis of shoreline changes was carried out using the DSAS (Digital Shoreline Analysis) method and analyzed by wind and sea wave factors in each season. The results of the analysis obtained LRR and EPR values for 5 years, the extent of changes in island land mass, the value of Hs and Ts from the results of wave forecasting using wind data. To simplify the analysis, Cemara Besar Island is divided into 9 segments based on variations in LRR values. The results show that in general Cemara Besar Island have very high accretion in segments A, B and E with an average of 3.61 m and very high abrasion occurred in segment F with an average of -1.01 m. Abrasion occurs with the greatest speed of change in segment A with an average of 4.64 m/year and the largest accretion rate in segment F with an average of -1.21791 m/year. Analysis of oceanographic factors through wave forecasting shows that in the west and transition I season, waves occur with Hs 1.21 m, greater than the eastern season and transition II season with Hs 0.91 m. wind direction from north dominant direction 377.50 in west season and transition I, and from east direction 67,25 in east season and transition I season. Direction of wind blowing influences wave propagation and direction of wave coming towards shore which affects sediment transport which produces accretion and abrasion on the Cemara Besar Island.

Applying geospatial technology in quantifying spatiotemporal shoreline dynamics along Marina El-Alamein Resort, Egypt.

Human interventions along the northwestern Egyptian Mediterranean coast recently interrupted the stability of Marina El-Alamein shoreline and resulted in spit evolution. Considering Egypt's vision 2030 for developing the northwestern Egyptian coast, continuous up-to-date monitoring programs became essential to ensure sustainability. This study, for the first time, aimed at coupling geospatial technology with Digital Shoreline Analysis System (DSAS) tool in monitoring, analyzing, and quantifying the impacts of anthropogenic activities on the spatiotemporal shoreline dynamics over the last 3 decades (1987-2017) at Marina El-Alamein resort, Egypt. In addition, the study carried out a quantitative geometrical temporal analysis for the newly formed spit from 2015 to 2020. The study used transect- and area-based approaches in estimating the shoreline changes for long- and short-term changes. The former approach computed the change in both the shoreline displacement and the rate of shoreline change, whereas the latter quantified the magnitude of spatial changes in the total land area. Results of the current study revealed that during 1987-2017, Marina El-Alamein shoreline experienced very high accretion, with an average rate of 2.8 ± 4.73m/year (end-point rate) and 2.52 ± 4.10m/year (linear regression rate). Quantitatively, Jetties #1 and #3 trapped sand on their western sides for a maximum distance of 706.31m and 406.5m, respectively. On the other hand, the eastern side of the resort experienced erosion with a maximum distance of 92.78m. Regarding changes in the total area, Marina El-Alamein's coast gained 1.130km2 (0.038km2/year) land and lost about 0.1115km2 (0.004km2/year) of its total area throughout the last 3 decades. During 2015, the continuous progressive accretion along the western side of J#1 resulted in the evolution of sand spit east of the jetty. Results of the temporal analysis showed that the spit's length was about 0.236km during May 2015 and reached 1.44km in April 2020 with an increment of 510.5% in length. In addition, the spit's total surface area increased by 33.606km2 in 5years (6.7212km2/year). Both the length and the area of the evolving spit grow annually with 102.11% and 108%, respectively. If this progressive accretion along the evolving spit continued, the lagoon's first inlet would probably suffer sedimentation that could cause its closure and deteriorate the lagoon's water quality. The study recommends carrying out an environmental impact assessment study for the newly formed spit to lessen its negative impact on the opposite tidal inlet and the lagoon's water quality.

Human Disturbances of Shoreline Morphodynamics and Dune Ecosystem at the Puerto Velero Spit (Colombian Caribbean)

Villate D. A.; Portz L.; Manzolli, R.P., and Alcantara-Carrio J., 2020. Human disturbances of shoreline morphodynamics and dune ecosystem at the Puerto Velero spit (Colombian Caribbean), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No.95, pp. 711-716. Coconut Creek (Florida), ISSN 0749-0208.Evolution of present coastal environments is controlled by both natural processes and anthropogenic activities, last one causing global, regional and local disturbances. This study analyze the effects of shortage of sediments from Magdalena River and tourism development in the recent shoreline morphodynamics and dune vegetation structure of the Puerto Velero spit, in the northern Colombian Caribbean coast. Shoreline position, dune vegetation and human occupation were taken from the interpretation of satellite images, aerial photographs and field trips. Three methods were applied to analyze shoreline migration. It allowed to deduce trends of very high erosion for the outer neck and moderate to high erosion for the inner neck, while the northern border and the point of the spit present an erosional trend in the outer and inner. Therefore, the outer neck and iner neck show predominance of an erosional trend, more intense for the outer one, while the northern border and particularly the point of the spit present trends of high and very high accretion. It implicates a present progradation of the spit, but a narrowing of its neck. The shortage of coastal sand due to the construction of a jettie at Magdalena River favored the formation of the spit by the erosion of the extinct Isla Verde barrier island, but currently cause erosion of the neck. Erosion of the outer and inner neck is also due to the impact of local disturbances on the backshore and dune system, mainly a rapid increase of occupation and a large circulation of people and vehicles. Dune vegetation distribution is affected by these disturbance, including the presence of invasive aloctonous Calotropis procera over a large area of the dune field. The natural climatic oscillations, particularly the negative El Nino Southern Oscillation (ENSO) events, also favor the progradation of the spit. The analysis of these disturbances on the present geomorphological and ecological evolution on the spit constitutes an important instrument for coastal management.

Thermal state of transiently accreting neutron stars with additional heating beyond deep crustal heating

Abstract As some neutron star transients require an additional unknown heat source (referred to as “shallow heating”) to explain their high temperatures at the beginning of quiescence, we investigate the effect of shallow heating as well as compressional heating on the thermal state of transiently accreting neutron stars with the use of evolutionary calculations in the present work. Through comparing our theoretical predictions of the equilibrium redshifted luminosities $(L_{\gamma}^{\infty})$ produced by both deep crustal heating and shallow heating/compressional heating for different time-averaged mass-accretion rates $\langle\dot{M}\rangle$ with 35 updated observations of soft X-ray transients, the results show that both shallow heating and compressional heating make significant contributions to the equilibrium redshifted luminosity. The hotter sources (XTE J1701, MAXI J0556, EXO 0748, Aql X-1 etc.) with higher accretion rates are more likely to be explained with the effect of shallow heating or compressional heating. In addition, for a proper shallow heat $q_\mathrm{sh}$ and mass-accretion rate $\dot{M}$, the effect of shallow heating could be simulated by compressional heating.