Добірка наукової літератури з теми "Macro-tidal shoreline"

Coasts are continually changing and remote sensing from satellite has the potential to both map and monitor coastal change at multiple scales. This study aims to assess the application of shorelines extracted from Multi-Spectral Imagery (MSI) and Synthetic Aperture Radar (SAR) from publicly available satellite imagery to map and capture sub-annual to inter-annual shoreline variability. This is assessed at three macro-tidal study sites along the coastline of England, United Kingdom (UK): estuarine, soft cliff environment, and gravel pocket-beach. We have assessed the accuracy of MSI-derived lines against ground truth datum tideline data and found that the satellite derived lines have the tendency to be lower (seaward) on the Digital Elevation Model than the datum-tideline. We have also compared the metric of change derived from SAR lines differentiating between ascending and descending orbits. The spatial and temporal characteristics extracted from SAR lines via Principal Component Analysis suggested that beach rotation is captured within the SAR dataset for descending orbits but not for the ascending ones in our study area. The present study contributes to our understanding of a poorly known aspect of using coastlines derived from publicly available MSI and SAR satellite missions. It outlines a quantitative approach to assess their mapping accuracy with a new non-foreshore method. This allows the assessment of variability on the metrics of change using the Open Digital Shoreline Analysis System (ODSAS) method and to extract complex spatial and temporal information using Principal Component Analysis (PCA) that is transferable to coastline evolution assessments worldwide.

Seawalls are commonly used worldwide to protect urbanized sea fronts. These alongshore protection structures are often blamed for hydro-sedimentary dynamics perturbations, but without clear and generalizable conclusions on long-term morphodynamic effects. In this paper, evolutions of beaches are studied from 1966 to 2021, comparing the urbanized sea front of Lacanau seaside resort (Aquitaine France) and adjacent natural areas. A large-scale spatiotemporal multisource dataset is used to derivate several indicators and evaluate the characteristics and magnitude of passive and active erosion related to a large riprap seawall at a highly energetic meso–macro tidal coast. The most dramatic manifestation of the presence of the seawall (passive erosion) is the beach lowering and the reduction of beach variability at the seasonal and interannual timescale in front of the seawall. However, recent evolutions are roughly similar at the seawall-backed beach than at the natural sector, indicating no specific active seawall influence on beach erosion or recovery. The perturbations directly attributable to the seawall (active erosion) are limited to temporary end-effect, slight perturbation of outer bar pattern and the setup of a slight platform around the depth of closure. The adverse effects are currently manageable, but they require a new strategy in view of the chronic shoreline retreat at adjacent sectors and the expected effects of climate change.

This research aims to evaluate the facies and facies association of the Yolde Formation at Kware stream in the Gongola Sub-basin of the Northern Benue Trough with objective of characterizing its paleodepositional environment. Six lithofacies consisting of trough crossbedded sandstone facies (St), massive bedded sandstone facies (Sm), planar crossbedded sandstone facies (Sp), ripple laminated sandstone facies (Sr), parallel sandstone facies (Sl) and mudstone facies (Fm) defining its stratal packages were skewed into distinctive assemblages of flaser, wavy and lenticular bedding. This present a fining upward signature with facies association typical of tidal flat system. This is evident of a coastal progradation with sequences reflecting migration of a supra-tidal mudflat over intertidal mixed-flat zone which progressively superposed subtidal sandflats. This is indicative of a coastal shoreline with a relatively progradational phase within the net transgressive regional framework of the Cretaceous Yolde Formation.

The coastline is influenced by wave action and is vulnerable to change in shape due to erosion or accretion. These changes occur largely as a result of longshore transport.

To predict such shoreline change there exist several different approaches, among which is the Crenulate Shaped Bay Method, researched by a team lead by Silvester, and sometimes known as Silvesters' method. In the frame of this project, after a short review of other approaches, this method was given deeper analysis.

From the analysis undertaken and the knowledge gained, several numerical models have been developed by the author, namely INTANG, NUMANG and EXISTP, to allow the Crenulate Shaped Bay Method to be applied to various Macro -Tidal beach conditions. Great detail has been undertaken in the development of the model INTANG which provides the user with a tool which interacts with the AutoCad environment.