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Cliffed (and rocky) coasts are geomorphic features occurring in about 80% of the coastline of the world and are strongly influenced by a broad range of both natural and anthropogenic processes that may cause serious erosion problems. Since the sea wave motion is a fundamental driver of cliff erosion, the cliffs become sensitive to increasing of global sea levels and to extreme weather events, which are both associated with global warming. Because of its importance, a considerable amount of investigations on coastal cliff erosion (CCE) were reported during the last decades. A bibliometric analysis is an useful tool to identify patterns of a given theme from a large body of academic literature. There is no previous evidence of a global bibliometric analysis in the literature in English on themes of CCE. Therefore, the aim of this article was to carry out a bibliometric analysis from Scopus database of CCE for the period 2000–2023. Once obtained, two filtering steps for selection of documents consisting of a custom R script implementation and a careful reading of the remaining documents were applied. During the search, a dynamic approach that puts emphasis on the processes operating on rocky coasts was selected instead of an evolutionary geological perspective. The final list reached 583 documents. A second aim was to discuss the research trends and challenges based on the latest highly-cited documents. As main result, the trend of the scientific production in the theme of CCE had an increasing interest over the last years, with an average compound annual growth rate of 15.6%. On the other side, the results demonstrated that even though the USA took the second place, European countries (United Kingdom, Italy, France, Portugal, Spain and Poland) lead the ranking; therefore, there is a scarcity of knowledge about the theme in large regions such as South America and Africa where seacliffs are dominants. [ABSTRACT FROM AUTHOR]

Context: Recently, Unoccupied Aerial Systems (UAS) with photographic or Light Detection and Ranging (LIDAR) sensors have incorporated on-board survey-grade Global Navigation Satellite Systems that allow the direct georeferencing of the resulting datasets without Ground Control Points either in Real-Time (RTK) or Post-Processing Kinematic (PPK) modes. These approaches can be useful in hard-to-reach or hazardous areas. However, the resulting 3D models have not been widely tested, as previous studies tend to evaluate only a few points and conclude that systematic errors can be found. Objectives: We test the absolute positional accuracy of point clouds produced using UAS with direct-georeferencing systems. Methods: We test the accuracy and characteristics of point clouds produced using a UAS-LIDAR (with PPK) and a UAS-RGB (Structure-from-Motion or SfM photogrammetry with RTK and PPK) in a challenging environment: a coastline with a composite beach and cliff. The resulting models of each processing were tested using as a benchmark a point cloud surveyed simultaneously by a Terrestrial Laser Scanner. Results: The UAS-LIDAR produced the most accurate point cloud, with homogeneous cover and no noise. The systematic bias previously observed in the UAS-RGB RTK approaches are minimized using oblique images. The accuracy observed across the different surveyed landforms varied significantly. Conclusions: The UAS-LIDAR and UAS-RGB with PPK produced unbiased point clouds, being the latter the most cost-effective method. For the other direct georeferencing systems/approaches, the acquisition of GCP or the co-registration of the resulting point cloud is still necessary. [ABSTRACT FROM AUTHOR]

Landslides are widely recognized as key components of landscape evolution in areas of steep topography. Here, we present a new framework for examining landslide inventories in the context of the volume‐based impact that different landslide sizes have on shaping the landscape, that is, their geomorphic effectiveness (GE). Focusing on an actively retreating coastal cliff in the Eastern Mediterranean and utilizing a LiDAR‐derived inventory of over 1,100 cliff landslides that occurred between 2014 and 2019, we show that segments of the cliff are characterized by two principal types of GE distributions: (a) A "humped" GE distribution where the accumulated erosion volume of the largest and rarest collapses in the inventory is similar or lower than that of more frequent, mid‐range collapses and (b) Nearly monotonically increasing GE distribution where the cumulative volume of larger collapses consistently surpasses that of smaller magnitude collapses. Regardless of the GE distribution type, we found that the cumulative geomorphic impact of the small and most probable collapses was negligible. Extending this new GE framework to 9 other previously published landslide inventories (coastal and mountainous), we demonstrate that precipitation and seepage‐induced landslide inventories are commonly characterized by monotonic‐type GE distributions, dominated by large landslides (>10−1 of the volume of the largest landslide), and that hump‐shaped GE distributions, dominated by more frequent mid‐size landslides, commonly occur under "dry" triggers (e.g., earthquakes). We propose that the humped GE distribution could reflect the lack of deep mechanical weakening, which exerts a higher probability of the largest landslides in the inventories triggered by "wet" factor. Plain Language Summary: Landslides are a vital component of landscape evolution and can cause catastrophic damage to infrastructure and human life. While larger landslides hold the potential to be the most destructive and effective events sculpting the landscape, their occurrence is relatively rare compared to smaller landslides that may be less destructive but occur more frequently. This study presents a new approach that examines the accumulated impact of different landslide magnitudes as a function of volume and frequency of occurrence. We suggest that the lithological setting and the triggering mechanism of landslides can determine which landslide magnitude will be more impactful. In all the analyzed landslide inventories (rainfall‐induced, wave‐induced, or earthquake‐induced), the cumulative impact of the small and most frequent landslides on shaping the landscape is negligible. In addition to identifying the most effective size of landslides in each environment, geomorphic effectiveness may also improve our understanding of future landslide activity under changing environmental conditions. Key Points: Geomorphic effectiveness (GE) is examined as a new framework for analyzing the volume and probability of landslide magnitudesThe most probable landslide magnitudes have a negligible direct physical impact, expressed by their relatively low accumulated volumeThe distribution of the GE of a landslide inventory is linked to the dominant trigger mechanism [ABSTRACT FROM AUTHOR]

The retreat of coastal cliffs is a natural process that occurs due to the interaction of different forcings that can be marine and atmospheric, and conditioned by the lithological properties of the rock material. Several attempts have been done at different scales to quantify and rank the various parameters that influence erosion rates, most of them agreeing that cliff retreat is governed by the lithological properties of the cliffs. Although, due to the large number of parameters involved there is not a clear consensus. The present study aims to characterize the cliffs along the Cantabrian coast by using an unsupervised classification of their physical and lithological characteristics, and by analyzing their retreat behavior. The proposed methodology is scalable to larger coastal areas. The study found that Cantabrian coastal cliffs have a low mean retreat rate of 0.042 m/year, with a maximum retreat rate of up to 0.4 m/year in two locations. Nine distinct groups of cliff behavior have been found, with only two of them presenting high erosional records, which are controlled by lithological features. Cliffs with the highest erosion rates are composed of alternating lithologies and more erodible materials. The results suggest that the factors most influencing erosive retreat in cliffs are the type of lithology and the alternation of different lithologies. • Automatic classification of coastal cliffs allows the detection of erodible clusters. • Coastal cliff erosion in Cantabria is governed by cliff orientation and the lack of a beach. • Low retreat rates are found in the Cantabrian coastal cliffs. • Automating cliff top identification would facilitate analysis on larger spatial scales. [ABSTRACT FROM AUTHOR]

The mechanisms through which wave action induces cliff erosion are not well quantified, which limits our ability to model future cliff erosion. Previous studies have investigated using seismic measurements of cliff‐top ground motion from wave impacts as a proxy for potential wave driven cliff erosion. However, most attention has focussed on averaged hourly statistics, rather than at the individual wave impact scale. Higher temporal resolution studies are needed to determine the extent to which frequent, low magnitude impacts transfer wave energy into cliff rock, compared to violent impacts that occur much less frequently. We carried out fieldwork in Taranaki, New Zealand on a cliff that is exposed to broken, breaking, and unbroken wave impacts at different tidal stages. Synchronized seismometer, wave gauge, and video data were collected to observe a range of wave impact types under different marine conditions. Approximately 7500 wave impacts were manually classified into eight groups according to the stage of wave transformation at impact using video data. Corresponding seismic signals were then analysed to compare ground motion and impact types. The greatest peaks in ground motion were associated with impact classes identifiable by the wave breaking just in front of, or onto the cliff face. Waves classed as broken and unbroken had a median displacement of 4.2 μm and 5.1 μm, respectively, whereas breaking wave impact classes had a median displacement value of 25.8 μm. Spectral analyses of impact types suggest that different impacts produce peaks in energy at different frequency bands, and the total energy transfer is higher for breaking wave impact classes. This research provides a first step in assessing the spectral signature of wave impacts at an individual wave scale, providing a new method to investigate wave–cliff interaction. [ABSTRACT FROM AUTHOR]

The Alcantara Launch Center (ALC) is the main Brazilian access to space. It is positioned over a complex terrain, and it has some important buildings for assembling, integration and launching activities, such as the Mobile Integration Tower. Being in a region of prevalent trade winds, the flow interaction between the complex terrain and the buildings can affect the safety of operations on the platform, and the dispersion of toxic gases emitted during the launching. The main objective of this work was to study the influence of topography and buildings on the atmospheric flow of ALC using computational fluid dynamics (CFD) techniques. Three geometries were considered: simplified terrain (case 1), smooth complex terrain(case 2), and roughness complex terrain (case 3). The flow conditions over ALC were simulated using the ANSYS Fluent 19.0 CFD commercial code. The numerical simulations used a realizable κ-ε to model turbulence effects and the results presented a good agreement with the in-situ field measurements for the most complex geometry (case 3). The topography clearly influences the flow pattern at ALC, with the cliff influence over the wind being the major cause for establishing the flow patterns.

The Alcantara Launch Center (ALC) is the main Brazilian access to space. It is positioned over a complex terrain, and it has some important buildings for assembling, integration and launching activities, such as the Mobile Integration Tower. Being in a region of prevalent trade winds, the flow interaction between the complex terrain and the buildings can affect the safety of operations on the platform, and the dispersion of toxic gases emitted during the launching. The main objective of this work was to study the influence of topography and buildings on the atmospheric flow of ALC using computational fluid dynamics (CFD) techniques. Three geometries were considered: simplified terrain (case 1), smooth complex terrain (case 2), and roughness complex terrain (case 3). The flow conditions over ALC were simulated using the ANSYS Fluent 19.0 CFD commercial code. The numerical simulations used a realizable κ-ε to model turbulence effects and the results presented a good agreement with the in-situ field measurements for the most complex geometry (case 3). The topography clearly influences the flow pattern at ALC, with the cliff influence over the wind being the major cause for establishing the flow patterns. [ABSTRACT FROM AUTHOR]

Leisner, M.M.; Paula, D.P.; Albuquerque, M.G.; Façanha, M.C.; Vasconcelos, Y.G., and Morais, J.O., 2024. Applications of UAV-SfM remote sensing in monitoring morphodynamic processes in sedimentary cliffs of Pacheco beach, Northeast Brazil. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 558-563. Charlotte (North Carolina), ISSN 0749-0208. Cliffs are steep morphologies, sculpted by the erosion of different types of rock and subject to mass movements. This study aims to evaluate the morphodynamic changes in a 700 m stretch of sedimentary sea cliffs located in northeastern Brazil using high-resolution images collected by UAV-SfM techniques to understand the geomorphic changes of the coastal landscape. The study used the Geomorphic Change Detection (GCD) method and CloudCompare's M3C2 algorithm applied to short-term monitoring. These tools use photogrammetric products (Elevation Models and Densified Point Clouds) to determine morphological changes in terms of erosion and deposition. The difference grid models are acquired by UAV-based remote sensing, which can accurately and efficiently provide very high-resolution images and digital surface model data to measure volumetric changes. The multi-temporal analysis revealed significant volumes of erosion throughout the cliff area during the study period. In the first interval (July/2023 - January/2024), the cliff recorded erosion in 18% of its area, with volumetric rates - 6,241 ± 1,230 m3 of erosion. In the second period (January/2024 to April/2024), more severe erosion rates were observed on the cliff, reaching -10,603 ± 1,504 m with 30% of its area eroded. This research has shown that sedimentary cliffs in northeastern Brazil are undergoing significant morphodynamic changes, with erosion rates increasing over time. The application of advanced remote sensing techniques, such as UAV-SfM and the GCD and M3C2 tools, reveals clear erosion patterns that vary according to the seasonal climatic processes (e.g., marine and subaerial) acting in the region under study. The results obtained are essential for understanding the geomorphological risks associated with coastal cliffs. In addition, they highlight the effectiveness of using UAVs for coastal monitoring, providing valuable information for the sustainable management of these vulnerable environments. [ABSTRACT FROM AUTHOR]

This work is devoted to the analysis of the landscape structure of the coastal cliffs of the Black Sea coast of the Caucasus. The paper analyzes the features of vegetation growth and the landscape structure of the cliffs of the Tuaphat massif, proposes and substantiates the classification of landscapes of coastal cliffs, reveals the features of coastal landscapes. In the landscape structure of the coastal cliffs of the Tuaphat massif, natural boundaries can be distinguished by: the nature of the apparent occurrence of geological layers; substates by the steepness of the slope; striae, which are characterized by more abundant growth of vegetation along cracks in the geological layer; facies usually coincide geographically with nanoand microforms of the relief and are usually represented by one type of vegetation (for example, a pillow rock form). The distribution of vegetation by striae on fine crushed stone of siltstone or mudstone, the absence of halophytes, but the predominance of salt-tolerant plant species with a wide ecological amplitude (petrophytes, cosmopolitans and ruderal) are typical.

Vrgada Island is situated in the central part of the eastern Adriatic coast. Upper Cretaceous limestones crop out on the surface and Pleistocene sediments cover them in some parts of the island. This study focused on a coastal cliff trending N - S on the northern part of the island. Aeolian-alluvial deposits, which are 12.5 m thick were analysed and three different facies in this succession described. The lowermost facies A highlights a strong aeolian influence marked by an increased silt percentage and was deposited during colder climate conditions. Sand and gravel in facies B were deposited by streams of dense, cold water formed by melting snow and ice from the nearby Dinaric mountains. The bioturbated sandy facies C was probably formed during a warmer climate. An unusually high percentage of augite in the lowermost part of facies A can be explained by the input of volcanic dust, most likely from the Roman or Campanian volcanoes in Italy. This, combined with the surface textures on quartz grains detected from SEM photographs indicates a short distance transport for the sediment, no matter which mechanism was dominant. The sediments from Vrgada Island represent a transitional zone between the north Adriatic islands, where aeolian sediments dominate and the South - Eastern Adriatic archipelago, where mixed alluvial and aeolian sediments were observed. [ABSTRACT FROM AUTHOR]

A geotechnical aspect of destruction processes of seashores was identified based on the case of erosion of Gdansk Bay Coast cliff formations. Causative factors of landslide were described in the context of natural phenomena, land development and its anthropogenic transformations. Possible directions of theoretical analysis of changes in ground-water relations were indicated.

Landslides and surface erosion are major processes controlling the progressive recession of many rocky cliffs along the Italian coastline. Nevertheless, many coastal settlements were built along cliffed sectors prone to rapid collapses. This represents a serious risk for tourists and living people, as well as for buildings, roads and railway networks. The densely urbanized coastline of the Campi Flegrei active volcanic district is one of the rocky coastal areas of South Italy mostly exposed to the recession. Here, coastal cliffs are made by volcaniclastic deposits and include remnants of ancient volcanic edifices formed in the last 15 ka. Due to petrographic, geotechnical and geostructural properties of volcaniclastic deposits, these cliffs have been affected by rapid recession since their origin. This research focuses on a cliff of the Campi Flegrei coastaline (Torrefumo, Monte di Procida) which, although currently protected from the sea waves by a seawall, is still retreating. We assessed the ongoing recession using a change detection analysis, based on accurate topographic data acquired with two terrestrial laser scanning surveys executed in 2013 and 2016. The quantitative comparison of 3D point clouds datasets allowed detecting 191 cliff failures. We verified that the frequency-magnitude distribution of the detached blocks followed an inverse power law, and most of the involved volumes were between 0.01 and 1 m3. Retreat rates of different cliff sectors varied from 0.001 to 0.025 m/year. Our analysis also allowed us to recognize slope failure mechanisms and distinguish rock falls from grain-by-grain surficial erosion. [ABSTRACT FROM AUTHOR]

Shore platforms, essential for coastal analysis and management, are poorly understood in terms of their long-term evolution, particularly regarding coastal cliff retreat rates and trends, despite their common presence in rocky coastlines. Rock coasts constitute fully erosional environments, yet long-term rates and trends of coastal cliff retreat remain poorly understood. This study adds to the limited number of studies that use cosmogenic isotopes to reconstruct millennial-scale cliff erosion. Cosmogenic 10Be concentrations were measured in 16 rock samples collected across an active 31 m wide granitic Jangsa shore platform in eastern Korea. A geometry-based inverse numerical model was used to simulate 10Be concentrations for various cliff retreat modes, relative sea level curves, and platform downwearing models. The model results were combined with measured concentrations to find the most likely scenario for coastal evolution. Our findings reveal that the shore platform has widened through time and is entirely formed during the Holocene, unlike the previous cosmogenic study in western Korea that attributed the formation of shore platforms to former interglacial periods. The results suggest acceleration in cliff retreat rate from 1.4 mm yr−1 at 7.4 kyr BP to 7.0 mm yr−1 at present. Accelerating cliff erosion may pose a threat to coastal communities, particularly in the context of observed and predicted anthropogenic sea level rise. • Numerical model simulates cosmogenic 10Be distribution across a shore platform in eastern Korea. • The granitic Jangsa shore platform was formed entirely during the Holocene. • Cliff retreat rate has accelerated 1.4 mm yr−1 at 7.4 kyr BP to 7.0 mm yr−1 at present. • Shore platform has widened by maintaining fixed seaward edge position and decreasing the slope. • First study to quantify millennial-scale cliff retreat rates on a granitic shore platform. [ABSTRACT FROM AUTHOR]

The recession of a coast can destabilize coastal cliffs. The stability of a cliff is controlled by a rock bridge. Identifying the volume-expansion point of rock bridges is crucial to assess cliff stability, but currently there are few identifying methods. Using a numerical analytical tool, we investigate the acoustic emission characteristics during shear tests on rock bridges. Acoustic emission events with a high energy level, i.e., characteristic events which occur at the volume-expansion point of rock bridges, can indicate this point. The characteristic events, the mainshock (the maximum event corresponding to rock-bridge rupture), and the smaller events between them constitute a special activity pattern, as the micro-seismicity during the evolutionary process of a coastal cliff collapse in Mesnil-Val, NW France showed. This pattern arises in rock bridges with different mechanical properties and geometry, or under different loading conditions. Although the energy level of characteristic events and mainshocks changes with the variation of the conditions, the difference of their energy level is approximately constant. The spatial distribution of characteristic events and mainshocks can indicate the location of rock bridges. These findings help to better understand the evolutionary mechanism of collapses and provide guidelines for monitoring the stability of coastal cliffs.

Coastal cliff erosion is caused by a combination of marine forcing and sub‐aerial processes, but linking cliff erosion to the environmental drivers remains challenging. One key component of these drivers is energy transfer from wave–cliff interaction. The aim of this study is to directly observe cliff ground motion in response to wave impacts at an individual wave scale. Measurements are described from two coastal cliff sites: a 45‐minute pilot study in southern California, USA and a 30‐day deployment in Taranaki, New Zealand. Seismometers, pressure sensors and video are used to compare cliff‐top ground motions with water depth, significant wave height (Hs) and wave impact types to examine cliff ground motion response. Analyses of the dataset demonstrate that individual impact events can be discriminated as discrete events in the seismic signal. Hourly mean ground motion increases with incident Hs, but the largest hourly peak ground motions occurred across a broad range of incident Hs (0.9–3.7 m), including during relatively calm conditions. Mean hourly metrics therefore smooth the short‐term dynamics of wave–cliff interaction; hence, to fully assess wave impact energy transfer to cliffs, it is important also to consider peak ground motion. Video analyses showed that the dominant control on peak ground motion magnitude was wave impact type rather than incident Hs. Wave–cliff impacts where breaking occurs directly onto the cliff face consistently produced greater ground motion compared to broken or unbroken wave impacts: breaking, broken and unbroken impacts averaged peak ground motion of 287, 59 and 38 μm s−1, respectively. The results illustrate a novel link between wave impact forcing and cliff ground motion response using individual wave field measurements, and highlight the influence of wave impact type on peak energy transfer to coastal cliffs. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper examines the spatial and temporal variations of cliff retreat rates over multi-temporal data of the Normandy cliffs. Data are derived from historical maps and aerial photographs and from recent lasergrammetry and photogrammetry monitoring. The diachronic analysis of all these data gives retreat rates of -0.1 to -0.5 m/yr. in line with the international literature. The spatial variations of the cliff retreat rates, at the Normandy scale, can be explained by geological structure, especially at the cliff foot, but also by the influence of cliff collapses or anthropogenic obstacles that disrupt the longshore drift. Multi-temporal data shows that the evolution of the cliffs occurs on scales from 10 to 70 years according to the lithology. The high resolution and frequency monitoring also provide information about the factors responsible for triggering gravitational landslides (rockfalls, slides, debris falls). The study proposes a regional warning threshold for the cliff characterized by landslides, under the dominating influence of rainfall and groundwater level evolution. In this respect the monitoring is inconclusive for chalk and limestone cliffs, because the origin of evolutions is more multifactorial (combination of more continental and marine processes). [ABSTRACT FROM AUTHOR]

Cliffs located along the Isotake coast, Shimane, Japan, are characterized by the development of indents without rockfalls and by the occurrence of rockfalls without indents—even though these cliffs have the same geology. An analytical method was developed to determine the mechanical properties of the rock surfaces of a coastal cliff. Twenty continuous impact repetitions of a Schmidt hammer were applied normal to the cliff surfaces in each test. The results of the tests (26 with indents and 22 without indents) showed a gradual increase in the rebound value with increasing number of repetitions. A new exponential equation was proposed in this study to describe the features of the weathered surfaces. The changes in the results were well approximated by this equation, and the approximation clearly distinguished between the two types of weathered surfaces, with higher rebound values at the surfaces of the cliffs with indents than at the surface of cliffs without indents. The homogeneity and heterogeneity of the surface and inner body of the cliff rock can also be modelled by the coefficients in this equation. [ABSTRACT FROM AUTHOR]

Previous studies have estimated that coastal cliffs exist on about 80% of the global shoreline, but have not been validated on a global scale. This study uses two approaches to capture information on the worldwide existence and erosion of coastal cliffs: a detailed literature survey and imagery search, and a GIS‐based global mapping analysis. The literature and imagery review show coastal cliffs exist in 93% of the combined recognized independent coastal states and non‐independent coastal regions worldwide (total of 213 geographic units). Additionally, cliff retreat rates have been quantified in at least one location within 33% of independent coastal states and 15% of non‐independent regions. The GIS‐based mapping used the near‐global Shuttle Radar Topography Mission 3 arc second digital elevation model and Arctic Coastal Dynamics Database to obtain near‐global backshore coastal elevations at 1 km alongshore intervals comprising about 1,340,000 locations (81% of the world vector shoreline). Backshore coastal elevations were compared with the mapped distribution of European coastal cliffs to produce a model training set, and this relationship was extended globally to map the likelihood of coastal cliff locations. About 21% of the transects (17% of the world vector shoreline) were identified as mangroves and eliminated as potential cliff locations. The results were combined with estimates of cliff percentages for Greenland and Antarctica from the literature, extending the global coverage to estimate cliff occurrence across 89% of the world vector shoreline. The results suggest coastal cliffs likely exist on about 52% of the global shoreline. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

[Display omitted] Caves in coastal cliffs in the Apostle Islands were analyzed for factors controlling their origin and evolution. Even though the Bayfield Group quartz sandstones were found to be of relatively low tensile strength, the traditional explanation attributing speleogenesis to localized zones of lithological and tectonic weakness does not adequately explain all geomorphic features of the caves. The caves were found to be formed by coalescence of smaller arcade-shaped cavities serially developed along subhorizontal discontinuities. In concordance with the previously formulated "arcade principle", positions and shapes of the cavities are defined by areas of reduced stress within the gravity-induced stress field. Evacuation of material from the rock massif can be attributed to wave action including the effect of water-pressurized air, and frost action. Compound cavities above the discontinuities tend to form "higher-order" arcade-like cavities/caves while those beneath more resistant strata rather develop into elongated overhangs similar to ordinary coastal notches. Propagation of the largest cavities, formed along steeply dipping joints and faults, is attributed to mass wasting and roof collapses. Similar examples of discontinuity-related cavities in coastal settings, suspectedly also controlled by gravity-induced stress distribution, can be found worldwide, being mostly concentrated to areas covered by ice sheets in the Pleistocene. The interplay between post-glacial isostatic uplift and Holocene lake-level rise is responsible for the development of mature forms of coastal caves in the Apostle Islands where present cliffs are estimated to have been exposed to the effects of wave action for the last 3–5 ky. [ABSTRACT FROM AUTHOR]

Abstract Coastal cliff recession represents a significant risk to both people and infrastructure, it is therefore important that we are able to efficiently monitor these environments to inform future management decisions. Through the use of UAV digital photogrammetry, we obtain point clouds to develop monthly models of the sea cliffs at Telscombe, East Sussex, UK between August 2016 and July 2017. The models captured were accurate to 0.05 m and had an average point density of 351 pts./m2. Using the methodology presented we were able to automatically detect rockfalls by undertaking a 2.5D surface change detection which populated monthly inventories through volumetric estimations. A total of 10,085 failures were observed with an estimated volumetric flux of 3889.4 m3 over the 12 month period of data collection. Due to the high frequency of data capture, successive block failures in the Newhaven Chalk formation were observed. The largest failure within the 12 month period was estimated at 2546.8 m3 and followed significant toe erosion due to wave action. The steepening of the cliff face was modelled through limit equilibrium analysis to determine the reduction in factor of safety for the months preceding failure. We then present a magnitude-frequency analysis using negative power laws from the monthly rockfall inventories for the entire study area. The negative power law models produced a strong correlation across all months with r2 values ranging from 0.97 to 0.99. The normalised power law scaling parameters ranged from 1.421 to 1.955 for β and from 33.79 to 904.14 for s. The observed rollover in power laws presented in previous research matches the resolution of the data presented in this study. Our results show that this method of data capture is comparable to existing methods whilst offering significant benefits in field surveying time and cost. Highlights • UAV photogrammetry models generated point clouds with 351 pts./m2. • Using a traditional photogrammetric approach accuracy was comparable to TLS. • 2.5D surface change detection revealed 10,085 failures with volume of 3889.4 m3. • Monthly monitoring of Newhaven chalk cliffs revealed successive blocks failures. • Negative power law models revealed strong correlations between 0.9697 and 0.9947. [ABSTRACT FROM AUTHOR]

Our understanding of sea‐cliff erosion processes and their response to recent and/or projected environmental changes such as sea‐level rise, climate change and anthropogenic development hinges on our ability to quantify sea‐cliff retreat rates and their variability through time. Here, we focus on Israel's Mediterranean 'Sharon' sea‐cliff as a case study for examining the significance of recent short‐term (i.e. annual to decadal) cliff‐top retreat rates that appear to exceed longer‐term rates of 'background' (i.e. centennial to millennial) retreat by 1–2 orders of magnitude. We demonstrate that an inherent sampling bias in rate estimates inferred from observation intervals shorter than process episodicity can also explain such a pattern. This potential ambiguity leads to a striking paradox where despite highly accurate and robust documentation of recent cliff‐top retreat, such as that obtained from aerial photographs and/or instrumental surveys, the short‐term retreat rates of episodically retreating sea cliffs remain poorly constrained. To address this key data gap along the Sharon sea cliff we employed a sediment budget approach that focuses on quantifying the continuous wave scouring of cliff‐collapsed material from the shore platform as a rate‐limiting process for episodic retreat of the cliff above. We used four high‐resolution (0.5 m/pixel) airborne LiDAR data sets acquired between 2006 and 2015 to determine short‐term maximum retreat rates of up to ~0.08 m/yr during this nine‐year period. These modern retreat rates compare to the cliff's background retreat rate of 0.03 to 0.09 m/yr since the mid‐Holocene, as determined herein from multiple geologic and archeological observations. Our results demonstrate that previously reported twentieth century cliff‐top retreat rates for this sea cliff, which range up to values of several meters per year, are biased and that sea‐cliff erosion rates have not yet been significantly impacted by recent environmental changes in the eastern Mediterranean basin, such as the restriction of sediment supply following emplacement of the Nile's Aswan dam system. © 2018 John Wiley & Sons, Ltd. Sea‐cliff retreat rates inferred from annual‐decadal observations of cliff‐top retreat are artefactually high because retreat episodicity has a time‐scale of several hundred years. Here, we use repeat airborne LiDAR to measure the continuous wave scouring of talus material from the cliff‐base as a rate‐limiting process for episodic retreat of the cliff itself above. Our results demonstrate that modern sea cliff erosion continues at background rates while rate estimates inferred from conventional measurements of recent cliff‐top retreat erroneously suggest otherwise. [ABSTRACT FROM AUTHOR]

Abstract The alongshore distribution of wave energy is believed to be an important control on the spatial variability of coastal erosion. There is, however, a lack of field data quantifying the alongshore variability in wave energy on rock coasts, whereby the relative control of coastline geometry versus foreshore characteristics on wave energy delivery remains unclear. A number of studies have identified high-frequency cliff-top ground shaking to be generated by wave impacts at the cliff toe during high tides (HT). To capture the variability of wave-cliff impact energy along-coast, we installed an array of cliff-top seismometers along a 1 km stretch of coastline in North Yorkshire, UK. Our aim is to constrain how wave energy transfer to the cliff toe varies, and to examine the relative energy transfer around typical coastline features, including a bay and headlands. Whilst the greatest HT ground motion energy is recorded at a headland and the lowest at the centre of the bay (5% of that observed at the headland), we identify no systematic alongshore variation in the HT ground motion energy that can be related to coastline morphology. We also note considerable variation between features of similar form: the total HT ground motion energy at one headland is only 49% of the next headland 1 km alongshore. Between neighbouring sites within the bay, separated by only 100 m, we observe up to an order of magnitude difference in ground motion energy transfer. Our results demonstrate the importance of the foreshore in driving the variations in energy delivery that we observe. Local alterations in water depth and foreshore topography control the alongshore distribution of wave energy available to generate cliff HT ground motions. Importantly, this apparently local effect overrides the influence of macroscale coastal planform morphology, which has previously been assumed to be the dominant control. The results show that foreshore characteristics that hold influence over wave energy transfer vary significantly over short (~100 m) distances, and so we expect erosion controlled by wave impacts to vary over similar scales. Highlights • Cliff-top ground motions vary significantly over short alongshore distances. • There is no systematic alongshore pattern in high-frequency ground motion energy. • Foreshore characteristics influence alongshore distribution of wave energy. • Foreshore characteristics override the influence of coastal planform morphology. • Foreshore characteristics that influence wave energy vary over short distances. [ABSTRACT FROM AUTHOR]

Geomorphic evolution of sea cliffs has significant impact on coastal settlements worldwide, so that evaluation of cliff instability processes, failure factors, and retreat rates involves a growing number of scientists for coastal risk and management purposes. Aerial photogrammetry and lidar are among the most used techniques for topographic characterization and geomorphic monitoring of coastal environments. A crucial role in the combined use of such techniques is the evaluation of different spatial accuracy and co-registration between derived terrain models, so that a robust error analysis is required. In this study, we present a change detection analysis of the Torrefumo coastal cliff, in the Campi Flegrei volcanic area (Southern Italy). Aerial images taken in 1956 and 1974, processed through digital photogrammetry, and an airborne lidar point cloud acquired in 2008 were used to produce Digital Elevation Models of the cliff. The analysis was based on the multi-temporal comparison of these models and included the calculation of volumetric changes and average retreat rates of the cliff face with reference to the 1956-1974 and 1974-2008 time intervals. The spatially variable elevation uncertainty of each Digital Elevation Model was evaluated with a probabilistic approach based on the fuzzy set theory. The results of this study showed significant eroded volumes during the period 1956-1974 and relatively smaller volumes in the 1974-2008 time span, with mean annual retreat rates of 1.2 m/year and 0.17 m/year, respectively. We infer that the significant decrease of erosion characterizing the second period was induced by the sheltering effect at the base of the cliff produced by the construction of a seawall in the early 80’s. [ABSTRACT FROM AUTHOR]

Large boulders have been found in marine cliffs from 7 study sites on Ibiza and Formentera Islands (Balearic Islands, Western Mediterranean). These large boulders of up to 43 t are located on platforms that form the rocky coastline of Ibiza and Formentera, several tens of meters from the edge of the cliff, up to 11 m above sea level and several kilometers away from any inland escarpment. Despite than storm wave height and energy are higher from the northern direction, the largest boulders are located in the southern part of the islands. The boulders are located in the places where numerical models of tsunami simulation from submarine earthquakes on the North African coast predict tsunami impact on these two islands. According to radiocarbon data and rate of growth of dissolution pans, the ages of the boulders range between 1750 AD and 1870 AD. Documentary sources also confirm a huge tsunami affecting the SE coast of Majorca (the largest Balearic Island) in 1756. The distribution of the boulders sites along the islands, the direction of imbrication and the run-up necessary for their placement suggest that they were transported from northern African tsunami waves that hit the coastline of Ibiza and Formentera Islands.

The distribution and morphological characteristics of the shelves around Salina Island have been analyzed and integrated with observations from onshore geological field studies in order to improve knowledge about its evolution, and to demonstrate how shelf width/depth can be used as proxies for reconstructing the development of the volcanic edifice. Insular shelves form essentially through marine erosion of volcanic centres during stages of reduced or inactive volcanism, and are representative of their original extension. Shelves having larger widths (commonly > 1000 m) and deeper edges (over 125 m depth) experienced wave erosion during successive cycles of sea-level fluctuations and subsidence after their formation, thus being indicative of a relatively older age of the eroded volcanic centres. Accordingly, we document offshore Salina the occurrence of presently submerged and largely dismantled volcanic centres (namely Pizzo Capo North and Fossa delle Felci South) predating the oldest subaerial products exposed on the adjacent coastal sectors. These offshore centres have subsided after their erosion and are no more documented on land. Furthermore, the finding of the largest and deepest shelf around the subaerial remnants of Pizzo di Corvo volcanic edifice allows relating it to an earlier stage of evolution of Salina, shedding light on contradictory radiometric ages on land. Narrower shelves (commonly < 1000 m) indicate a lower evolutionary maturity with respect to the larger ones; they are, in fact, formed along the sectors of the island where younger volcanic products are exposed, such as to the north and south of Monte dei Porri. The depths of the shelf edges, mostly at − 110 m (in the areas not affected by later mass-wasting), suggest that these coastal sectors were relatively stable or even slightly uplifted after erosion during Last Glacial Maximum. Moreover, several interacting factors (such as lithology of volcanic products, fetch and exposure to prevailing storms, degree of submarine erosion, relative sea level changes) have been taken into account to explain the morphological setting of the different shelf and coastal sectors of Salina. On the whole, our results show the importance of integrated field and marine studies to unravel the geological evolution of insular volcanoes and to obtain inferences on their vertical mobility. [ABSTRACT FROM AUTHOR]

A composite fall-slippage model is proposed in this study for the Tertiary sedimentary coastal cliffs of Varkala in the western coastal tract of Peninsular India which are retreating landwards due to the combination of several factors. The fall model in the present study accounts both spring seepage and wave action, resulting in undercutting and this fall affects only the topmost laterite and the just below sandstone in the cliff. Slippage in this area affects all the litho-units and hence the geologic characteristics of all the litho-units are considered for developing the slippage model. This mathematically derived model can be used in other cliffs exhibiting the same morphology as well as the one controlled by the same influencing factors. This model differs from other models in incorporating multi-lithounits as well as multi-notches. Varkala cliffs form a part of the aspiring geopark in the Global Geopark Network and hence a study on the cliff recession is a pressing requirement. [ABSTRACT FROM AUTHOR]

Neste trabalho analisam-se as características espectrais da turbulência atmosférica na região do Centro de Lançamento de Alcântara (CLA), que sofre a influência de uma falésia e da brisa marítima provinda do oceano, visando obter informações sobre a estrutura turbulenta do local. Determinaram-se os espectros das 3 componentes do vento (u, v e w) na camada limite superficial sobre esse terreno homogêneo, visando aplicações no Projeto e Desenvolvimento dos foguetes de sondagem e do Veículo Lançador de Satélite (VLS) realizado pelo IAE. Os dados foram coletados no mês de agosto do ano de 1999 através de um anemômetro sônico tridimensional. Também se obteve resultados envolvendo as relações σu/u*, σv/u* e σw/u*, todos condizentes com os previstos na literatura.In this work is analyzed the spectral characteristics of atmospheric turbulence in the Alcântara Launching Center (CLA), which suffers the influence of a cliff and of the sea breeze coming from the ocean. The atmospheric spectra were determined for the 3 wind components (u, v, and w) in the superficial boundary layer, to be used for the Research and Developpment (R&D) of sounding rockets and Satellite Launch Vehicle (VLS) build by IAE. The data were collected during the month of August, 1999 using a 3D sonic anemometer. Results involving the σu/u*, σv/u* and σw/u* relations are obtained, and are all consistent with those reported in literature.

En este trabajo se analiza el relieve de la vertiente occidental de la Cordillera de la Costa del norte de Chile, la cual está caracterizada por la ocurrencia del gran Acantilado Costero. El objetivo central de este estudio es establecer los controles tectónico-climáticos en la configuración del relieve del borde costero del norte de Chile. La metodología utilizada consiste básicamente en un estudio detallado del relieve mediante índices geomorfológicos cuantitativos tales como grado de incisión, curvas e integrales hipsométricas, perfiles de thalweg e índice de sinuosidad. Estos índices se aplicaron a modelos de elevación digitales e imágenes satelitales. Los resultados más relevantes muestran que el relieve de la vertiente occidental de la Cordillera de la Costa exhibe creciente incremento de la intensidad de la erosión al aumentar la latitud. Este incremento no es uniforme; procesos relacionados con la tectónica como subsidencia/alzamiento litoral y actividad de fallas, y por otra parte la erosión de la paleotopografía de la Cordillera de la Costa debido a los procesos ligados a la construcción del Acantilado Costero y el aumento de la precipitación, afectan la morfología del relieve del borde costero del norte de Chile. La existencia y excelente preservación del Acantilado Costero resulta de un marcado desequilibrio entre las tasas de alzamiento y las tasas de erosión, cuya diferencia es de una a dos órdenes de magnitud, controlada por el marco climático de hiperaridez extrema del Desierto de Atacama que se ha mantenido por lo menos desde los últimos 2 Ma. Las variaciones en la intensidad de la erosión desde el norte hacia el sur se interpretan como resultado del incremento en la tasa de precipitación en un orden de magnitud en esa misma dirección.This work analyzes the morphological features of the western margin of the northern Chile Coastal Cordillera, character-ized by the presence of a major Coastal Cliff The main purpose of this research is to better understand the tectonic and climatic controls on the topography. The methodology used consists basically of a detailed study of the topography with quantitative geomorphic indexes such as incisión grade, hypsometric curves and integráis, thalweg profiles and sinuosity index. These are applied to digital elevation models and satellite images. The main results show that the topography of the western margin of the Coastal Cordillera, exhibits an increasing intensity of the erosión with latitude. This increment is non uniform. The tectonic processes that produced coastal subsidence/uplift and fault activity, and the erosión of the paleotopography of Coastal Cordillera due to processes related with the construction of the Coastal Cliff and increasing rainfall, modify the morphology of the coastal border of northern Chile. The existence and conservation of the Coastal Cliff results from the existance of non-equilibrium between the uplift and erosión rates. Both rates have one-two order magnitude difference, controlled by the extreme hyperarid climate of the Atacama Desert. These conditions prevailed at least for the last 2 m.yrs. The variations in the intensity of the erosión from north to south are interpreted as the result of the southward increase in precipitación by one order of magnitude.