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 planform coastlines with many bays and capes, such as parts of the coastline of Great Britain. The algorithm automatically and sequentially delineates and smooths 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 non-smoothed raster and smoothed vector coastlines, normals to the coastline (as vector shape files), xyz profiles (as comma-separated-value, CSV, files), and the cliff top and toe (as point shape files). The algorithm also automatically assesses the quality of 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 manually digitized boundaries by numerous professionals. Also, we assess the reproducibility of the results using different DEM resolutions (5, 10 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 the manually digitized uncertainty. The code and a manual are publicly available on a GitHub repository.
Highlights
Coastal cliff erosion is a worldwide hazard with impacts on coastal management, infrastructure, safety, coastal resilience, and the local and national economies
Cliff metric delineation has traditionally been done by manually digitizing cliffs
We present an automatic cliff toe/top delineation algorithm based on profile elevation extraction from a digital elevation model (DEM), using a fixed profile length, and an automatic generation of a generalized coastline that is suitable for very irregular coastline shapes
Summary
Coastal cliff erosion is a worldwide hazard with impacts on coastal management, infrastructure, safety, coastal resilience, and the local and national economies. The increasing population of coastal zones has led to the accelerating occupation of cliff tops and faces by buildings and infrastructure, including areas that are seriously threatened by shoreline retreat (Del Río and Gracia, 2009). The impact of this increased human presence has exacerbated erosion problems in some places. Cliff metric delineation has traditionally been done by manually digitizing cliffs. A. Payo et al.: Development of an automatic cliff delineation lineation of cliffs and other shoreline features remains timeconsuming and somewhat dependant on the analyst’s interpretation
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