Study on Spatiotemporal Evolution of the Yellow River Delta Coastline from 1976 to 2020

The Yellow River Delta in China is the most active one for sea–land changes over all deltas worldwide, and its coastline evolution is critical to urban planning and environmental sustainability in coastal areas. Existing studies rarely used yearly temporal resolution, and lack more detailed and quantitative analysis of coastline evolution characteristics. This paper used visual interpretation to extract the coastline of the Yellow River Delta in year interval Landsat images for 45 years from 1976 to 2020, and analyzed the spatiotemporal characteristics of the coastline evolution through statistical methods such as calculating change values and change rate. The main results are as follows: (1) overall, the coastline of the Yellow River Delta presented a spatial pattern involving northern landward retreat and southern seaward expansion. Since 1990, the Yellow River Delta has entered a period of decline. In addition, the length of the artificial coastline increased by about 55 km; (2) in the Qingshuigou region, the land area and the coastline length increased first and then stabilized. The southeastern part of the Qingshuigou was in a state of erosion, while the northeastern part was expanding toward the sea along the north direction; (3) in the Diaokou region, the land area has been decreasing, but the reduction rate has gradually slowed down. The main conclusions are as follows: (1) through the research on the evolution model and mechanism of the coastline of the Yellow River Delta, it was found that human factors and natural factors were the two major driving factors that affect the evolution of the coastline; (2) a river branch appeared in the northern part of the Qingshuigou region in 2014 and became a major branch in 2020, which would affect the development of the coastal region of Chengdao. This study is important for better understanding the evolution pattern of the Yellow River Delta coastline and will help to provide guidance for coastline management and resource exploitation.

CliffDelineaTool v1.1.0: an algorithm for identifying coastal cliff base and top positions

Correct quantification of coastal cliff erosion requires accurate delineation of the cliff face bounded by the cliff top and base lines. Manual mapping is time consuming and relies on mapper's decisions and skills. Existing algorithms are generally site specific and may be less suitable for areas with diverse cross-shore cliff geometry. Here we describe CliffDelineaTool (v1.1.0), a MATLAB-based algorithm that identifies cliff base and top positions on complex cliffs using cross-shore transects extracted from digital elevation models. Testing on four 750–1200 m cliffed coastlines shows that the model performance is comparable to manual mapping and provides some advantages over existing models but provides poor results for cliff sections with ambiguous cliff top edges. The results can form the basis for a range of analyses including coastal inventories, erosion measurements, spatio-temporal erosion trends, and coastline evolution modelling.

The Coastline Evolution Model 2D (CEM2D) V1.1

Coasts are among the most intensely used environments on the planet, but they also present dynamic and unique hazards, including flooding and erosion. Sea level rise and changing wave climates will alter patterns of erosion and deposition, but some existing coastline evolution models are unable to simulate these effects due to their one-dimensional representation of the systems or the sediment transport processes. In this paper, the development and application of the Coastline Evolution Model 2D (CEM2D) are presented, a model which incorporates these influences. The model has been developed from the established CEM and is capable of simulating fundamental cause–effect relationships in coastal systems. The two-dimensional storage and transport of sediment in CEM2D, which are only done in one-dimension in CEM, mean it is also capable of exploring the influence of a variable water level on sediment transport and the formation and evolution of morphological features and landforms at the mesoscale. The model sits between one-dimensional and three-dimensional models, with the advantage of increased complexity and detail in model outputs compared to the former but with more efficiency and less computational expense than the latter.

Géomatique appliquée à la géomorphologie littorale : Contribution à la connaissance théorique des techniques d’analyse spatiale de l’évolution du linéaire côtier

L’analyse de l’évolution du trait de côte en cinématique du littoral exige tout d’abord le choix d’un indicateur linéaire. En effet, il existe plus d’une douzaine de lignes de référence matérialisant la position du trait de côte. Cette diversité d’indicateurs induit la recherche et la mise au point de nombreuses méthodes pour détecter, extraire et suivre la mobilité du trait de côte. Ces approches méthodologiques reposent sur la compilation et la comparaison de données acquises, soit sur le terrain par des instruments de topométrie (niveau de chantier, théodolite, tachéomètre électronique, lidar, récepteur DGPS, etc.), soit en laboratoire par le traitement numérique d’images satellites ou aériennes. Le but de ce travail est de contribuer à une meilleure connaissance de l’approche cartographique et statistique qui permet de calculer les taux de variation historique du trait de côte à travers les outils la géomatique: Télédétéction et Système d’Information Géographique (SIG). La technique faisant l’objet d’étude dans cette approche est une méthode statistique d’extrapolation et de calcul de tendances basée sur le traitement des images géospatiales. Dans un cadre théorique, le sujet discute la définition de la ligne de référence, du protocole méthodologique de son extraction et de la cartographie de l’évolution du trait de côte du littoral. The analysis of coastline evolution in coastal kinematics requires first of all the choice of a linear indicator. Indeed, there are more than a dozen reference lines materializing the position of the coastline. This diversity of indicators leads to the research and development of numerous methods to detect, extract and monitor coastline mobility. These methodological approaches are based on the compilation and comparison of data acquired either in the field by topometry instruments (site level, theodolite, electronic tacheometer, lidar, DGPS receiver, etc.) or in the laboratory by digital processing of satellite or aerial images. The aim of this work is to contribute to a better knowledge of the cartographic and statistical approach that allows the calculation of historical coastline variation rates through geomatics tools: Remote sensing and GIS. The technique studied in this approach is a statistical method of extrapolation and calculation of trends based on the processing of geospatial images. In a theoretical framework, the subject discusses the definition of the reference line, the methodological protocol of its extraction and the mapping of the coastline evolution.

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

Study on the Coastline Evolution in Sopot (2008–2018) Based on Landsat Satellite Imagery

The coastline is the boundary between the water surface in a reservoir or watercourse and the land, which is characterised by high instability and functional diversity. For these reasons, research on coastal monitoring has been conducted for several decades. Currently, satellite images performed with synthetic aperture radars (SARs) are used to determine its course and variability together with high-resolution multispectral imagery from satellites such as IKONOS, QuickBird, and WorldView, or moderate-resolution multispectral images from Landsat satellites. This paper analysed the coastline variability in Sopot (2008–2018) based on Landsat satellite imagery. Furthermore, based on multispectral images obtained, it was determined how the beach surface in Sopot changed. Research has shown that the coastline keeps moving away from the land every year. This was particularly noticeable between 2008 and 2018 when the coastline moved on average 19.1 m towards the Baltic Sea. Moreover, it was observed that the area of the sandy beach in Sopot increased by 14 170.6 m2, which translates into an increase of 24.7% compared to 2008. The probable cause of the continuous coastline shift towards the sea and the increase of the beach surface is the oceanographic phenomenon called tombolo, which occurred in this area as a result of the construction of a yacht marina near the coast.

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.