Development of an automatic delineation of cliff top and toe on very irregular planform coastlines (CliffMetrics v1.0)

Abstract

Abstract. We describe a new algorithm that automatically delineates the cliff top and toe of a cliffed coastline from a Digital Elevation Model (DEM). The algorithm builds upon existing methods but is specifically designed to resolve very irregular 15 planform coastlines with many bays and capes, such as parts of the coastline of Great Britain. The algorithm automatically and sequentially delineates and smooth shoreline vectors, generates orthogonal transects and elevation profiles with a minimum spacing equal to the DEM resolution, and extracts the position and elevation of the cliff top and toe. Outputs include the nonsmoothed-raster and smoothed-vector coastline, normals to the coastline-(as vector shapefiles), xyz profiles (as commaseparated-value files), and the cliff top and toe (as point shape files). The algorithm also automatically assesses the quality of 20 the profile and omits low-quality profiles (i.e. extraction of cliff top and toe is not possible). The performance of the proposed algorithm is compared with an existing method, which was not specifically designed for very irregular coastlines, and to handdigitized boundaries by numerous professionals. Also we assess the reproducibility of the results using different DEM resolutions (5 m, 10 m and 50 m), different user defined parameter-sets related to the degree of coastline smoothing, and the threshold used to identify the cliff top and toe. The model output sensitivity is found to be smaller than hand-digitized 25 uncertainty. Code and a manual are publicly available on a github repository.

Open Digital Shoreline Analysis System: ODSAS v1.0

“…The results are then compared at both an aggregated level (i.e., metrics for all transects combined) and at a transect-by-transect individual level. For this work, we have used the SAGA v 7.9.1 GIS CliffMetrics tool [13] and have developed two new algorithms: the ProfileCrossings tool for SAGA GIS (https://bgs.sharefile.eu/share/getinfo/s26266 f461c343cba, accessed on 25 November 2021) and the CoastCR for R (both new codes, explained herein).…”

“…The baseline transects are generated using SAGA-CliffMetrics (version 1.0) [13] from the same baseline used in DSAS but employed in a points format. This tool generates the transects by a series of vector and raster operations and, therefore, requires a digital elevation model (DEM) as an input file.…”

“…Like DSAS, our proposed method uses a single baseline and allows the user to choose different smoothing and spacing options to generate the transects. Our method differs from DSAS in the way that the smoothing determines the transect orientation by combining raster and vector objects [13]; we also use free open-source software (FOSS), SAGA [14] and the FOS R [15] programming language. Herein, we will refer to our proposed method as the open digital shoreline analysis system (ODSAS).…”

Acoustic Evidence of Shallow Gas Occurrences in the Offshore Sinú Fold Belt, Colombian Caribbean Sea

“…Acoustic blanking (AB) zones appear as a reflection of great amplitude with extensions between 350 and 700 m. Their upper surface has a flat geometry that completely masks the entire underlying sequence due to the total absorption of seismic energy (Figures [4][5][6][7][8]. This is the reason why AB shows up as an acoustically transparent zone in many sections.…”

“…The study of submarine, coastal, and insular areas in the world has been widely developed in recent decades [1][2][3][4][5]. This is particularly thanks to the development of technologies and methods in the acoustic, geodesic, geophysical, and remote sensing fields, as well as the improvement in geospatial data management [6][7][8][9][10][11][12]. The incorporation of new methods for the exploration of deep environments has allowed researchers to detect and map shallow gas accumulations in marine deposits [13][14][15].…”