Geomorphometric analysis of a rocky coastline: an example from Hornsund, Svalbard

We describe a method to extract a number of quantitative morphometric characteristics of a rocky coastline. The algorithm, which is implemented in the free open-source software GNU Octave, takes as its input an ordered set of coordinate pairs defining the coastline. It finds vertices of specific angularity at two different levels, first approximating convex features (headlands) and then looking for local maxima (embayment edges) in their vicinity. It extracts numerical parameters for each embayment delimited by the former points, including basic geometric parameters (e.g. area, depth and width) and coefficients expressing shapes of embayments (e.g. form factor, coefficient of asymmetry and compactness). These we adapted from morphometric studies of other geomorphic features. Complex headlands and random sectors of the coastline which are delimited by embayment edges are automatically removed. The method was developed and tested on Hornsund in Svalbard, where 20 headlands, 28 embayment edges and 20 embayments were identified, but could be adapted to a wide range of coastal situations. We consider a range of possible applications of the methods, including to the classification of coastlines, change detection and identifying controls on their morphologies, and we discuss the choice of optimum parameters for the algorithm.