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Coastal cliffs : morphology and management
\"This book offers an insight into the global occurrence, geomorphology, evolution, weathering and erosion of coastal cliffs and bluffs. Stabilization and preservation of cliffs are treated in detail. Mitigation of cliff hazards and preservation of scenic features and sites of scientific importance requires effective coastal cliff management that can only be based on thorough knowledge of the physical processes at work. Cliffs have been cut in various geological formations, and have taken shape as a sequel to a world-wide sea level rise. Most cliffs have receded as the result of weathering and erosion, but some are now stable. Where they are actively receding, consuming useful agricultural or forested land or threatening coastal structures such as roads, buildings and seaside towns, it may be necessary to halt their retreat, or at least to modify it, by coastal cliff management\"--Provided by publisher.
Book
Controls on Ice Cliff Distribution and Characteristics on Debris‐Covered Glaciers
Ice cliff distribution plays a major role in determining the melt of debris‐covered glaciers but its controls are largely unknown. We assembled a data set of 37,537 ice cliffs and determined their characteristics across 86 debris‐covered glaciers within High Mountain Asia (HMA). We find that 38.9% of the cliffs are stream‐influenced, 19.5% pond‐influenced and 19.7% are crevasse‐originated. Surface velocity is the main predictor of cliff distribution at both local and glacier scale, indicating its dependence on the dynamic state and hence evolution stage of debris‐covered glacier tongues. Supraglacial ponds contribute to maintaining cliffs in areas of thicker debris, but this is only possible if water accumulates at the surface. Overall, total cliff density decreases exponentially with debris thickness as soon as the debris layer reaches a thickness of over 10 cm. Plain Language Summary Debris‐covered glaciers are common throughout the world's mountain ranges and are characterized by the presence of steep ice cliffs among the debris‐covered ice. It is well‐known that the cliffs are responsible for a large portion of the melt of these glaciers but the controls on their formation, development and distribution across glaciers remains poorly understood. Novel mapping approaches combined with high‐resolution satellite and drone products enabled us to disentangle some of these controls and to show that the ice cliffs are generally formed and maintained by the surface hydrology (ponds or streams) or by the opening of crevasses. As a result, they depend both at the local and glacier scale on the dynamic state of the glaciers as well as the evolution stage of their debris cover. This provides a pathway to better represent their contribution to glacier melt in predictive glacier models. Key Points We derived an unprecedented data set of 37,537 ice cliffs and their characteristics across 86 debris‐covered glaciers in High Mountain Asia We find that 38.9% of the cliffs are stream‐influenced, 19.5% pond‐influenced and 19.7% are crevasse‐originated Ice cliff distribution can be predicted by velocity, as an indicator of the dynamics and state of evolution of debris‐covered glaciers
Journal Article
Exploring QSAR models for activity-cliff prediction
Introduction and methodology
Pairs of similar compounds that only differ by a small structural modification but exhibit a large difference in their binding affinity for a given target are known as activity cliffs (ACs). It has been hypothesised that QSAR models struggle to predict ACs and that ACs thus form a major source of prediction error. However, the AC-prediction power of modern QSAR methods and its quantitative relationship to general QSAR-prediction performance is still underexplored. We systematically construct nine distinct QSAR models by combining three molecular representation methods (extended-connectivity fingerprints, physicochemical-descriptor vectors and graph isomorphism networks) with three regression techniques (random forests, k-nearest neighbours and multilayer perceptrons); we then use each resulting model to classify pairs of similar compounds as ACs or non-ACs and to predict the activities of individual molecules in three case studies: dopamine receptor D2, factor Xa, and SARS-CoV-2 main protease.
Results and conclusions
Our results provide strong support for the hypothesis that indeed QSAR models frequently fail to predict ACs. We observe low AC-sensitivity amongst the evaluated models when the activities of both compounds are unknown, but a substantial increase in AC-sensitivity when the actual activity of one of the compounds is given. Graph isomorphism features are found to be competitive with or superior to classical molecular representations for AC-classification and can thus be employed as baseline AC-prediction models or simple compound-optimisation tools. For general QSAR-prediction, however, extended-connectivity fingerprints still consistently deliver the best performance amongs the tested input representations. A potential future pathway to improve QSAR-modelling performance might be the development of techniques to increase AC-sensitivity.
Graphical Abstract
Journal Article
Comparison of 3D Model Generation Using Structure-from-Motion by Open-Source Software and Validation with LiDAR for Revealing Changes in Eroding Coastal Cliffs
Zaitseva-Pärnaste, I. and Herrmann, H., 2024. Comparison of 3D model generation using Structure-from-Motion by open-source software and validation with LiDAR for revealing changes in eroding coastal cliffs. 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. 1054–1058. Charlotte (North Carolina), ISSN 0749-0208. Precise 3D modeling of coastal areas is a crucial tool for monitoring, forecasting, and thereby facilitating the management of coastal processes. This study explores the efficacy of Structure-from-Motion (SfM) technology, utilizing open-source software OpenDroneMap and COLMAP, for 3D modeling of coastal cliffs, comparing it to the more costly LiDAR method. It assesses model quality, including precision and the ability to detect small, potentially catastrophic faults not visible in 2D orthophotos. The paper evaluates each software's features, such as georeferencing, user-friendliness, and performance on High-Performance Computing systems, against drone-based LiDAR benchmarks. The study reveals that the evaluated open-source packages generate good quality models: OpenDroneMap provides automatic georeferencing, while COLMAP produces a slightly higher quality model but without automatic georeferencing, which is a necessity for natural environments. COLMAP automatically chooses a parameter set to produce a high-quality model with a precision of 10 cm or better, but the parameters remain unknown to the user, making manual adjustment challenging. OpenDroneMap, on the other hand, makes manual adjustment of the parameters easier but also requires more parameter tweaking to achieve the same accuracy as COLMAP. While LiDAR has been extensively utilized for coastal monitoring, SfM is typically considered a secondary method due to the significant effort required to achieve high-quality results, including the need for high-quality photographs, georeferencing, and extended data processing times. However, this paper introduces a paradigm shift by demonstrating the feasibility of using SfM as an independent and effective method for assessing coastal cliff erosion, provided that suitable software is employed. The study evaluates two open-source software options for generating 3D models via SfM, verifying their effective performance. This revelation presents a promising avenue for cost-efficient coastal cliff monitoring, suggesting that with the right tools, SfM can stand on equal footing with LiDAR in terms of reliability and effectiveness.
Journal Article
Cliff Notching Due To Swash Abrasion: Insights From Physical Experiments
Notch development at the base of sea cliffs is an important control on cliff recession rates, but a detailed mechanistic understanding of notch formation by swash abrasion is lacking. We conducted physical experiments, using homogeneous erodible rock simulants, to study notch‐forming mechanisms under periodic sediment‐laden bore impacts. Our findings reveal shifts in the temporal dynamics of notch development. Initially, swash uprush and vortex formation contribute to a positive feedback loop that creates a shallow and wide notch. Subsequently, upward erosion ceases, and notch backwear and downwear are dominated by the vortex. Eventually, sediment deposition armors the notch floor; this negative feedback loop reduces erosion. The sediment size determines the amount of erosion, with a range of grain sizes generating maximum erosion. This indicates a dependence on the momentum of the sediment particles entrained within the bore. This research reveals fundamental notch formation mechanisms driven by swash abrasion. Plain Language Summary When waves attack a rock cliff, they gradually undercut the cliff and remove materials, forming a wave‐cut notch. Studying how notches form and develop in natural settings takes a very long time, so we created a weaker cliff in the laboratory using easily eroded foam. The cliff was exposed to repeated impacts from bores carrying sediment, representing the impact of broken waves. Notch formation is observed over a few hundred hours. Initially, the notch is wide and shallow. As it grows, abrasive sediment cannot be propelled into the roof, stopping the upward expansion of the notch, and sediment piles up at the bottom, blocking further downward erosion. The notch continues to deepen, but at a decreasing rate. The size of the beach sand or gravel has an important influence on the erosion rate. If the sediments are too large or too small, little erosion occurs, whereas sediments of a certain size can cause rapid erosion. This is because waves need to be able to entrain sediment and hurl it with sufficient force against the cliff to cause erosion. Key Points Controlled laboratory experiments with repeated swash impacts reveal positive and negative feedback mechanisms in abrasion notch formation Notch geometry varies over time and is determined by swash impact location, vortex formation and sediment deposition Grain size modulates beach shape and sediment‐laden bore momentum, collectively influencing notch development
Journal Article
Evaluation of the Apple iPhone 12 Pro LiDAR for an Application in Geosciences
Traditionally, topographic surveying in earth sciences requires high financial investments, elaborate logistics, complicated training of staff and extensive data processing. Recently, off-the-shelf drones with optical sensors already reduced the costs for obtaining a high-resolution dataset of an Earth surface considerably. Nevertheless, costs and complexity associated with topographic surveying are still high. In 2020, Apple Inc. released the iPad Pro 2020 and the iPhone 12 Pro with novel build-in LiDAR sensors. Here we investigate the basic technical capabilities of the LiDAR sensors and we test the application at a coastal cliff in Denmark. The results are compared to state-of-the-art Structure from Motion Multi-View Stereo (SfM MVS) point clouds. The LiDAR sensors create accurate high-resolution models of small objects with a side length > 10 cm with an absolute accuracy of ± 1 cm. 3D models with the dimensions of up to 130 × 15 × 10 m of a coastal cliff with an absolute accuracy of ± 10 cm are compiled. Overall, the versatility in handling outweighs the range limitations, making the Apple LiDAR devices cost-effective alternatives to established techniques in remote sensing with possible fields of application for a wide range of geo-scientific areas and teaching.
Journal Article
Advances in exploring activity cliffs
The activity cliff (AC) concept is of comparable relevance for medicinal chemistry and chemoinformatics. An AC is defined as a pair of structurally similar compounds with a large potency difference against a given target. In medicinal chemistry, ACs are of interest because they reveal small chemical changes with large potency effects, a concept referred to as structure–activity relationship (SAR) discontinuity. Computationally, ACs can be systematically identified, going far beyond individual compound series considered during lead optimization. Large-scale analysis of ACs has revealed characteristic features across many different compound activity classes. The way in which the molecular similarity and potency difference criteria have been addressed for defining ACs distinguishes between different generations of ACs and mirrors the evolution of the AC concept. We discuss different stages of this evolutionary path and highlight recent advances in AC research.
Journal Article
Assessment of Moraine Cliff Spatio-Temporal Erosion on Wolin Island Using ALS Data Analysis
The aim of the article is to present the temporal and spatial variability of the cliff coast erosion of the Wolin Island in 2012–2020 in three time periods (2012–2015, 2015–2018, 2018–2020). The research used data from airborne laser scanning (ALS), based on which DEM models were made. Based on the differences between the models, the amount of sediment that was eroded by the sea waves was determined. The conducted research showed that, in the analyzed period, the dynamics of the Wolin cliffs were characterized by high variability. The greatest erosion was observed on sandy cliffs, and the smallest on clay cliffs and on cliffs that are densely covered with vegetation. In the sediment budget studies, two seashore erosivity indicators were proposed: length-normalized sediment budget (LB) (m3/m) and area-normalized sediment budget (AB) (m3/m2). The average annual dynamics of the cliff edge erosion on the Wolin Island was found to be LB = 6.6 ± 0.3 m3/m/a, AB = 0.17 ± 0.01 m3/m2/a. The results obtained are comparable with other postglacial cliffs. The use of the differential analysis of DEM models allows for the determination of the dynamics of the cliff coast and may be used in spatial development and planning of seashore protection zones.
Journal Article