Coastline Evolution Research Articles

Multi-scale approach to analyse the evolution of soft rock coastal cliffs and role of controlling factors: a case study in South-Eastern Italy

The evolution of soft rock coastlines is strictly related to natural and anthropogenic conditions, which in some cases can determine also an acceleration of coastal retreat. The recent evolution of a soft rocky coastal stretch on the Italian southern Adriatic sector is analysed. To investigate the most important contributing factors to coastal evolution, a detailed multi-temporal (1954–2017) morphological analysis with photo-interpretation is carried out, which allows gaining a general understanding of the cliff evolution. The coastal retreat was then evaluated by exploiting the Digital Shoreline Analysis System (DSAS) tool. From that, site-specific analyses are carried out to explore the role of four environmental factors: rock mechanical properties, geostructural setup of the rock mass along the coast, emerged rock platform at the toe, and the storm waves. Analyses highlighted how the most significant retreat is detected along cliff segments characterized by the presence of low strength rocks susceptible to water-induced weakening, moderate fracturing degree of the rock mass, absence of the emerged platform at the toe, and wave storms. This work shows how a multi-scale methodology could represent an efficient approach to gain an interpretation of the instability processes and thus prepare risk mitigation plans and land management strategies.

One-Line Modeling of Mega-Nourishment Evolution

Whitley, A.E.; Figlus, J.; Valsamidis, A., and Reeve, D.E., 2021. One-line modeling of mega-nourishment evolution. Journal of Coastal Research, 37(6), 1224–1234. Coconut Creek (Florida), ISSN 0749-0208. As many coastal areas of the world suffer from chronic erosion, innovative solutions beyond traditional local nourishment must be explored. One such solution is the implementation of mega-nourishments (MNs), where a large sediment volume is deposited in a single location and redistributed via natural processes, thereby feeding adjacent beaches. Robust numerical modeling methods are needed to evaluate potential MN sites at coastal locations around the world. Two one-line numerical modeling approaches of MN evolution are presented using the Coastline Evolution Model (CEM) and GENESIS + Cascade (GenCade). Both models are parameterized for the Sand Motor (SM) that has been constructed on the Dutch coast to explore the feasibility of the MN approach. Here, a variety of K coefficients in the Coastal Engineering Research Center (CERC) sediment transport equation are tested since traditionally calibrated and used values may not apply for MN features. Both models are found capable of reproducing the shoreline morphological patterns observed at the SM over the first 3.5 years. GenCade shows a low difference between measured and modeled coastline position overall, showing accurate predictions of absolute shoreline position. CEM is able to capture feature tip migration due to its wave shadowing algorithm. The best results from both models can be obtained for higher K values than those commonly suggested in the literature. Given the size of a mega-nourishment relative to traditional nourishments, it is likely that a higher-than-usual K value may be a better fit when simulating mega-nourishments in a one-line model.

REDUCED COMPLEXITY MODELING OF SHORELINE RESPONSE BEHIND OFFSHORE BREAKWATERS

Prediction of the shoreline response behind offshore breakwaters is essential for coastal protection projects. Due to the complexity of the processes behind the breakwaters (e.g., wave diffraction, currents, longshore transport), detailed modelling needs high computational efforts. Therefore, simplifying the process effect in a simpler coastline model could be efficient. In this study, the coastline evolution model ShorelineS is used. A new routine was implemented in the model to adjust the wave heights and angles behind the offshore breakwaters. Two approaches from the literature and a newly introduced one were tested in this study. The model free grid system was used to simply track the breaker line; such an advantage also helped to form tombolo, which is not common for these types of models. The tests showed promising results for single and multi breakwaters systems; however, the newly introduced approach still needs further testing and refinement for better performance and less computational cost.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/mdCpmSQFO1Y

An approach to coastline evolution as a tool for coastal management: case study of La Pedrera—Cabo Polonio Bay (Rocha, Uruguay)

A study of the position of the coastline was performed from the recent past (50 years) to Holocene ages (about 5000 years ago) in La Pedrera–Cabo Polonio coastal sector, in the southeast of Uruguay. Some persistent geoforms, such as marshes, located at very low elevations present lowest displacement of the recent coastline. Other recent landscapes, such as coastal gullies, developed on Late Pleistocene sediments are associated with a progradational coast in the short term. The geomorphological cartography was a useful tool for coastal management in the scenario of 10 cm sea-level rise per century and a coastal retreat of about 1 m per year. The analysis of coastline evolution provides information to assess the best measures to prevent coastal erosion and identify vulnerable areas. The presence of an escarpment (paleo coastline) located around + 10 to + 5 m above the current sea level appears to be the most appropriate criterion of minimum setback distances from current coastlines for constructions.

Holocene evolution of the wave-dominated embayed Moruya coastline, southeastern Australia: Sediment sources, transport rates and alongshore interconnectivity

Sediment budgets on wave-dominated coastlines are important in determining shoreline behaviour and are primarily inherited from geological-scale coastal evolutionary history. Sediment compartments provide a framework to conceptualise and investigate sediment budgets over a range of time and space scales. This study aims to assess the sediment budget for a secondary coastal compartment on the New South Wales (NSW) south coast ∼26 km in length and containing five adjacent but discrete Holocene coastal bay barriers: Barlings Beach, Broulee Beach, Bengello Beach, Moruya Heads Beach and Pedro Beach. Building on earlier morphostratigraphic studies, a new series of Optically Stimulated Luminescence (OSL) ages are presented for foredune ridge sequences at previously un-dated sites. Additional Ground Penetrating Radar (GPR) transects complement earlier stratigraphic datasets, and seamless topographic and bathymetric LiDAR datasets provide insight into subaerial coastal deposits and inner shelf morphology in this region. The results demonstrate that barriers within the compartment have two different sediment sources. The barriers are dominated by shoreface supply of quartz-rich sand transported onshore as shoreface morphology evolved towards equilibrium. Skeletal carbonate sand became an important component of the sediment budget for the northern Barlings and Broulee beaches after ∼3000 years ago. Shoreline progradation at Bengello Beach has been steady throughout the mid-to late- Holocene. Bengello contains the largest volume of Holocene sand and accreted at an average rate of 3.1 m3/m/yr (for the current shoreline length). The other barrier systems have experienced changes in sediment accumulation rate as their shorelines prograded seaward resulting in changes to their alongshore interconnectivity. Rapid filling of the Pedro Beach embayment by ∼4000 years ago initiated headland bypassing and northward sand transport to Moruya Heads Beach which only then commenced progradation. In contrast, as Broulee and Bengello Beaches prograded they converged in the lee of Broulee Island forming a tombolo which led to division of the former continuous shoreline into two. A marked increase in skeletal carbonate content at Broulee occurred after this separation attesting to the restriction of the southern quartz-sand source replaced by local carbonate production. This study emphasises the importance of understanding the long-term temporal variability in sediment budget and embayment interconnectivity in determining shoreline response to changing boundary conditions such as sea level and wave climate as well as contemporary anthropogenic influences.

Coastline evolution: The rise and fall of sea level through time

Coastline evolution: The rise and fall of sea level through time

A Holistic Modeling Approach to Project the Evolution of Inlet-Interrupted Coastlines Over the 21st Century

Approximately one quarter of the World’s sandy beaches, most of which are interrupted by tidal inlets, are eroding. Understanding the long-term (50-100 year) evolution of inlet-interrupted coasts in a changing climate is therefore of great importance for coastal zone planners and managers. This study therefore focuses on the development and piloting of an innovative model that can simulate the climate-change driven evolution of inlet-interrupted coasts at 50-100 year time scales, while taking into account the contributions from catchment-estuary-coastal systems in a holistic manner. In this new model, the evolution of inlet-interrupted coasts is determined by: (1) computing the variation of total sediment volume exchange between the inlet-estuary system and its adjacent coast, and (2) distributing the computed sediment volume along the inlet-interrupted coast as a spatially and temporally varying quantity. The exchange volume, as computed here, consists of three major components: variation in fluvial sediment supply; basin (or estuarine) infilling due to the sea-level rise-induced increase in accommodation space; and estuarine sediment volume change due to variations in river discharge. To pilot the model, it is here applied to three different catchment-estuary-coastal systems: the Alsea estuary (Oregon, USA), Dyfi estuary (Wales, UK), and Kalutara inlet (Sri Lanka). Results indicate that all three systems will experience sediment deficits by 2100 (i.e. sediment importing estuaries). However, processes and system characteristics governing the total sediment exchange volume, and thus coastline change, vary markedly among the systems due to differences in geomorphic settings and projected climatic conditions. These results underline the importance of accounting for the different governing processes when assessing the future evolution of inlet-interrupted coastlines.

Assessment and Quantification of the Accuracy of Low- and High-Resolution Remote Sensing Data for Shoreline Monitoring

Τhe accuracy of low-resolution remote sensing data for monitoring shoreline evolution is the main issue that researchers have been trying to overcome in recent decades. The drawback of the Landsat satellite archive is its spatial resolution, which is appropriate only for low-scale mapping. The present study investigates the potentialities and limitations of remote sensing data and GIS techniques in shoreline evolution modeling, with a focus on two major aspects: (a) assessing and quantifying the accuracy of low- and high-resolution remote sensing data for shoreline mapping; and (b) calculating the divergence in the forecasting of coastline evolution based on low- and high-resolution datasets. Shorelines derived from diachronic Landsat images are compared with the corresponding shorelines derived from high-spatial-resolution airphotos or Worldview-2 images. The accuracy of each dataset is assessed, and the possibility of forecasting shoreline evolution is investigated. Two sandy beaches, named Kalamaki and Karnari, which are located in Northwestern Peloponnese, Greece, are used as test sites. It is proved that the shorelines derived from the Landsat data present a displacement error of between 6 and 11 m. The specific data are not suitable for the shoreline forecasting procedure and should not be used in related studies, as they yield less accurate results for the two study areas in comparison with the high-resolution data.

The First Video Witness of Coastal Boulder Displacements Recorded during the Impact of Medicane “Zorbas” on Southeastern Sicily

Over the last few years, several authors have presented contrasting models to describe the response of boulders to extreme waves, but the absence of direct observation of movements has hindered the evaluation of these models. The recent development of online video-sharing platforms in coastal settings has provided the opportunity to monitor the evolution of rocky coastlines during storm events. In September 2018, a surveillance camera of the Marine Protected Area of Plemmirio recorded the movement of several boulders along the coast of Maddalena Peninsula (Siracusa, Southeastern Sicily) during the landfall of the Mediterranean tropical-like cyclone (Medicane) Zorbas. Unmanned autonomous vehicle (UAV) photogrammetric and terrestrial laser scanner (TLS) surveys were performed to reconstruct immersive virtual scenarios to geometrically analyze the boulder displacements recorded in the video. Analyses highlighted that the displacements occurred when the boulders were submerged as a result of the impact of multiple small waves rather than due to a single large wave. Comparison between flow velocities obtained by videos and calculated through relationships showed a strong overestimation of the models, suggesting that values of flow density and lift coefficient used in literature are underestimated.

Prediction of Shoreline Evolution. Reliability of a General Model for the Mixed Beach Case

In the present paper, after a sensitivity analysis, the calibration and verification of a novel morphodynamic model have been conducted based on a high-quality field experiment data base. The morphodynamic model includes a general formula to predict longshore transport and associated coastal morphology over short- and long-term time scales. With respect to the majority of the existing one-line models, which address sandy coastline evolution, the proposed General Shoreline beach model (GSb) is suitable for estimation of shoreline change at a coastal mound made of non-cohesive sediment grains/units as sand, gravel, cobbles, shingle and rock. In order to verify the reliability of the GSb model, a comparison between observed and calculated shorelines in the presence of a temporary groyne deployed at a mixed beach has been performed. The results show that GSb gives a good agreement between observations and predictions, well reproducing the coastal evolution.

Influence of the El Niño Phenomenon on Shoreline Evolution. Case Study: Callao Bay, Perú

Analyzing the long-term behavior of the coastlines in the vicinity of river mouths and estuaries usually relies on the mean (predicted) values of the sediment discharge from the river. However, this approach does not consider low frequency, severe events, such as El Niño (EN), that can have a large effect on coastlines. While the effects of an EN on flooding and droughts are well studied, little information exists about its effects on coastal zones, and especially on the evolution of coastlines. In early 2017, an EN occurred in the equatorial Pacific Ocean, and the country of Peru was affected with high precipitation levels, and extreme river discharges and flooding. During this event, in the district of Lima, the Rimac River discharged a huge amount of sediment into the Callao Bay, and the shoreline accreted approximately 1 km, demonstrating the significant effects that an EN can have on coastal zones. To explore these effects, this paper studies the influence of an EN on shoreline evolution in the Callao Bay by analyzing Landsat images from 1985–2019 to understand the shoreline evolution and identify changes to the coastline. Results show that when an extraordinary EN occurs (e.g., 1982–1983, 1997–1998, and 2017), the shoreline experiences high accretion compared to when a smaller, or no EN occurs. During these events, a significant delta forms at the south end of the bay, and the redistribution of the accumulated sediment by wave action causes the accretion of the adjacent coastlines for as far as 7 km north of the river mouth. This shows the importance of these events for the wellbeing of coastlines adjacent to river mouths affected by EN.

UAV Photogrammetry and Ground Surveys as a Mapping Tool for Quickly Monitoring Shoreline and Beach Changes

The aim of this work is to evaluate UAV photogrammetric and GNSS techniques to investigate coastal zone morphological changes due to both natural and anthropogenic factors. Monitoring morphological beach change and coastline evolution trends is necessary to plan efficient maintenance work, sand refill and engineering structures to avoid coastal drift. The test area is located on the Northern Adriatic coast, a few kilometres from Ravenna (Italy). Three multi-temporal UAV surveys were performed using UAVs supported by GCPs, and Post Processed Kinematic (PPK) surveys were carried out to produce three-dimensional models to be used for comparison and validation. The statistical method based on Crossover Error Analysis was used to assess the empirical accuracy of the PPK surveys. GNSS surveys were then adopted to evaluate the accuracy of the 2019 photogrammetric DTMs. A multi-temporal analysis was carried out by gathering LiDAR dataset (2013) provided by the “Ministero dell’Ambiente e della Tutela del Territorio e del Mare” (MATTM), 1:5000 Regional Technical Cartography (CTR, 1998; DBTR 2013), and 1:5000 AGEA orthophotos (2008, 2011). The digitization of shoreline position on multi-temporal orthophotos and maps, together with DTM comparison, permitted historical coastal changes to be highlighted.

Geoarchaeological investigation of the Quriyat coastal plain (Oman)

Due to the richness of its coastal environments, particularly lagoons and mangrove, the low-lying areas of the Omani coastline attracted settlements very early. However, the low-lying coasts are highly mobile landscapes, whose evolution is controlled by multiple factors acting at different timescales, from episodic (extreme events) to millennial timescales (gradual shoreline changes). From a geoarchaeological analysis (geomorphological mapping, archaeological survey, core drilling, and sedimentological, faunic and microfaunic analyses), this study proposes for the first time to reconstruct the landscape evolution of the Quriyat coastal plain landscape during the Mid-Late Holocene. Results indicate a coastal landscape dominated by large lagoons and mangroves during the mid-Holocene (5th millennium). Between 6712 -6501 cal. BP and 6183−5992 cal. BP, an extreme wave event identified as a tsunami, is registered in the southern part of the coast. Between 4223−3984 cal. BP and 4150−3981 cal. BP, lagoons were quickly clogging over more than 3.5 km in favour of the development of sebkhas or dune fields. We suggest this rapid evolution is related to erosional crises linked to the setting up of arid conditions in this part of the Omani coast. The production of several sea-level index points shows a great stability of the relative sea-level over the last 6.000 yearscal. BP and point out the predominant role of sedimentary infilling in the coastline evolution of Quriyat. The high sedimentation rates, added to the exposure of coastal hazards, partially explains the relatively low density of archaeological sites found in the Quriyat coastal plain, despite the presence of major shell-midden (Khor Milk I and II), which attest the old attractiveness of this sector. From geoarchaeological and taphonomic points of view, the Quriyat area is considered as having non-favourable conditions for the preservation of archaeological remains.

Combination of Aerial, Satellite, and UAV Photogrammetry for Mapping the Diachronic Coastline Evolution: The Case of Lefkada Island

Coastline evolution is a proxy of coastal erosion, defined as the wasting of land along the shoreline due to a combination of natural and/or human causes. For countries with a sea border, where a significant proportion of the population lives in coastal areas, shoreline retreat has become a very serious global problem. Remote sensing data and photogrammetry have been used in coastal erosion mapping for many decades. In the current study, multi-date analogue aerial photos, digital aerial photos, and declassified satellite imagery provided by the U.S. Geological Survey (USGS), Pleiades satellite data, and unmanned aerial vehicle images were combined for accurate mapping of the southwestern Lefkada (Ionian Sea, Greece) coastline over the last 73 years. Different photogrammetric techniques were used for the orthorectifation of the remote sensing data, and geographical information systems were used in order to calculate the rates of shoreline change. The results indicated that the southwest shoreline of Lefkada Island is under dynamic equilibrium. This equilibrium is strongly controlled by geological parameters, such as subsidence of the studied shoreline during co-seismic deformation and mass wasting. The maximum accretion rate was calculated at 0.55 m per year, while the respective erosion rate reached −1.53 m per year.

Temporal (1948–2012) and Dynamic Evolution of the Wouri Estuary Coastline within the Gulf of Guinea

The Wouri estuary is located in the Gulf of Guinea on the Atlantic coast of Cameroon’s coastline plain (3°49′ and 4°04′ north latitude and 9°20′ to 9°40′ east longitude), and is strongly influenced by coastal dynamics that have remained unquantified over a long period of time. This study analyzed the historical evolution of the Wouri estuarine coastline between 1948 and 2012. Variations in the estuarine evolution of the Wouri were studied from (i) minute topographic extracts from 1948, (ii) 1996–1999 nautical charts, and (iii) 2012 spatial map vectors. The net temporal spatial variation rates were calculated using the statistical methods of the Digital Shoreline Analysis System (DSAS). These change rates were also calculated over two time intervals (1948–1996 and 1996–2012) and over a 64-year period (1948–2012). The study reveals highly disparate results. Indeed, kinematics show that the Wouri estuary was dominated by erosion in its downstream section, with 262.83 ha for –3.2 m/year and 110.56 ha for –5.8 m/year between 1948–1996 and 1996–2012 respectively, and by accretion on the other hand in its upstream section, with 239.17 ha for 4.3 m/year in zone 5 between 1948–1996 and 150.82 ha for 12.6 m/year in zone 4 between 1996–2012. Thus, over the 64-year period (1948–2012), we have a dominance of variation by erosion downstream and conversely by accretion upstream, marked by the presence of amplifying factors (anthropogenic pressure and climate change) of the rate of variation of morphological evolution at the beginning of the 21st century, as compared to the middle-20th century. The observed development of sediment loss and accumulation, both influences and will influence, the sediment regime along the Wouri estuarine coastline. There is a need to develop a systematic sub-regional coastal surveillance activity to effectively manage Cameroon’s coastline system.

Pluriannual beach-dune evolutions at regional scale: Erosion and recovery sequences analysis along the aquitaine coast based on airborne LiDAR data

Abstract: With apparent uniformity, the 230 km of the Aquitanian sandy coast presents many differences in geomorphological characteristics and evolutions at the event, seasonal, annual and pluriannual time scales. This contribution highlights work based on extensive airborne LiDAR coverage campaigns realized in 2011, 2014, 2016 and 2017. Geomorphological evolutions are studied at the scale of the sedimentary cells and subcells of the Aquitanian sandy coast, specifically through the automatic detection of dune erosion scarps and incipient foredunes, planimetric indicators analysis, and the sediment budget of the beach-dune interface. Analyses were performed for two periods: 2011–2014 (including the erosional impact of the 2013–2014 winter) and 2014–2017, presenting continuous and extensive beach recovery at the beach-dune interface. Dune erosion scarps and incipient foredune characteristics are analyzed. A classification based on the alongshore length of the erosion scarp shows great diversity of erosional dynamics, which are directly linked to the geomorphologic characteristics of the beach sediment availability and the nearshore bar system. This diversity includes homogeneously large erosional bands above a 1 km alongshore length, periodic Mega cusp embayments from 200 to 800 m, and a local erosion mark less than 200 m long. Analysis for the following period shows a prompt and massive recovery at the upper beach and dune foot proxies on the majority of the coast. However, the recovery process as well as erosion is strongly marked by a North–South gradient. The dune front was massively impacted in Gironde, with a retreat exceeding 25 m that was poorly prograded since 2014, whereas in Landes a progradation of the front dune is observed compared to 2011. During the first period (including the 2013–2014 winter), more than 15 500 × 103 m3 of sediment was eroded from the beach-dune interface, which represents on average a loss of 66 m3 per linear meter. The gains during the following period (2014–2017) are also massive, above 13 500 × 103 m3, with an average gain of 57 m3 per linear meter. Given the budget between the two periods, 86.5% of the sand eroded in 2014 had moved back in 2017 at the beach-dune interface but 90 % of the sand stocks are localised between the upper beach and the dune foot. The progressive recovery tendency at the beach-dune interface is massive but fragile because the sediments are potentially removable by storm marine processes in case of energetic events. At the pluriannaual, decadal and pluridecadal scales, the different sections of the coast follow various trends concerning erosion as well as recovery processes resulting in a contrasted long term coastline evolution from the north to the south of the coast.

Coastline evolution based on statistical analysis and modeling

Abstract. Wind, waves, tides, sediment supply, changes in relative sea level and human activities strongly affect shorelines, which constantly move in response to these processes, over a variety of timescales. Thus, the implementation of sound coastal zone management strategies needs reliable information on erosion and/or deposition processes. To suggest a feasible way to provide this information is the main reason for this work. A chain approach is proposed here, tested on a vulnerable coastal site located along southern Italy, and based on the joint analysis of field data, statistical tools and numerical modeling. Firstly, the coastline morphology has been examined through interannual field data, such as aerial photographs, plane-bathymetric surveys and seabed characterization. After this, rates of shoreline changes have been quantified with a specific GIS tool. The correlations among the historical positions of the shoreline have been detected by statistical analysis and have been satisfactorily confirmed by numerical modeling, in terms of recurrent erosion–accretion area and beach rotation trends. Finally, based on field topographic, sediment, wave and wind data, the response of the beach through numerical simulation has been investigated in a forecasting perspective. The purpose of this study is to provide a feasible, general and replicable chain approach, which could help to thoroughly understand the dynamics of a coastal system, identify typical and recurrent erosion–accretion processes, and predict possible future trends, useful for planning of coastal activities.

Coastline dynamics of the northern Lower Casamance (Senegal) and southern Gambia littoral from 1968 to 2017

Northern Lower Casamance and southern Gambia's beaches, just like those of West Africa, are subject to significant morpho-sedimentary dynamics characterized by coastline mobility. Such mobility, combined with significant variations in different places, is characterized by some globally erosive trend (−1.2–6 m/year, in sandy areas extending from Senegal to Sierra Leone and −1 to −15 m/year from Ivory Coast to Nigeria). The purpose of this article is to analyze the coastline evolution in Lower Casamance and southern Gambia based on a diachronic survey (1968–2017). The reference line used to demonstrate the variation of the coastline is the vegetation boundary.The results obtained are based on the digital processing of geospatial data (aerial photographs, Landsat and Google Earth images).The different variations of the coastline are obtained through the calculation of two indexes considered as the most relevant ones. The first one, the End Point Rate (EPR) index, helped measure the difference between two successive coastlines and the second one, the Linear Regression Rate (LRR) index, allows assessing the ability to estimate the evolution of each segment over the entire period considered. These mobility indexes (EPR and LRR) show some variable dynamics of the coastline, featured by two trends: the first one, under accretion in the 1968–1986 period and the other one, globally erosive during 1986–2017 period.

Mapping the Sandy Beach Evolution Around Seaports at the Scale of the African Continent

In Africa, several new seaport developments are being considered. In sedimentary environments, such port developments can have adverse impacts on the evolution of adjacent coastlines. To learn from past port engineering practice, we created a unique database containing the coastline evolution and characteristics of 130 existing African seaports. Whereas the systematic mapping of coastal impacts was previously hampered by data availability, innovative automated satellite image processing techniques have enabled us to intercompare ports at an unprecedented continental scale. We found large geographical differences with respect to the beach evolution. The total detected changes in the beach area between 1984 and 2018 totaled 44 km2, of which ca. 23 km2 is accretion and ca. 21 km2 is erosion. The top 10% “hotspot” ports account for more than 65% of these changes. These hotspots exhibit common characteristics, namely: they are located on open coastlines, have large alongshore sediment transport potential, and have large cross-shore breakwaters. Although these driving characteristics are well established in coastal engineering theory, our results indicate that the beaches adjacent to the existing seaports have been and remain seriously affected by these drivers. Our results can be used to inform beach maintenance strategies for existing seaports and to support planners and engineers to minimize long-term coastal impacts of port expansions and new port developments in Africa in the future.

Evolution of Yellow River Delta Coastline Based on Remote Sensing from 1976 to 2014, China

Coastal regions are threatened by natural processes, such as erosion driven by storm surges and the effect of jetties, as well as by human behavior. The coastline of the Yellow River Delta (YRD) was monitored using the general high-tide line method, which combines Remote sensing (RS) and geographic information system (GIS) technology, using multi-spectral scanner (MSS), thematic mapper (TM), and enhanced thematic mapper plus (ETM+) images of the YRD from 1976 to 2014 as a data source. The results demonstrated that the shape and length of the YRD coastline has changed dramatically since 1976. The course of the Diaokouhe channel has resulted in mainly inland erosion in the north, and is primarily marine erosion; therefore, it was termed an erosion-type estuary. However, the coastline of the Qingshuigou course has moved seaward, demonstrating an accretion stage, and was therefore termed an accretion-type estuary. The coastline advanced forward before 1997 and shrank after 2003 in the southern part of the river mouth, which was due to the shift in the river mouth in 1996. It has continually extended outward in the northern part of the river mouth from 2003 onward. The coastline in the southern part of the river mouth has moved randomly, with the occurrence of both erosion and sedimentation caused by land reclamation and sea wave intrusion. In most cases, the coastline has extended offshore, especially in the northern part of the river mouth. The YRD coastline has changed frequently and rapidly from 1992 to 2014. The river mouth channel, river water and sediments, and precipitation were the major factors affecting the YRD. The YRD coastline was mainly in an accretion stage during flow periods. The erosion rate decreased and tended to be stable during a dry period. The coastline was basically stable when dry periods occurred over a long period. The location of Yellow River ports and sea erosion were the main factors driving coastline changes. The coastline was mainly influenced by the flow path of the Yellow River, with recent human activity also becoming a factor.