Spatial analysis of eroding surface micro-topographies

Abstract

Analysis of the spatial variability in erosion rates at the micro-scale has the potential to improve our understanding of how shore platforms erode. Comparing the erosion rate of a single measurement reading with the erosion rate of other increasingly distant readings would indicate whether average variation in erosion rate is homogeneous and at what spatial scale. Little variation in erosion rate from one measurement reading as distance increased would indicate that an area is eroding homogeneously and that the surface measured is responding as a single spatial unit. An increase or decrease in the variation in erosion rate difference with increasing distance from one reading would suggest that the area was not acting as a single spatial unit and that surface responses differ with scale. This study used a two-year dataset of traversing micro-erosion meter (TMEM) readings, collected from two limestone shore platforms on the north of Malta, at Ponta tal-Qammieħ and Blata l-Bajda, in order to explore the relationship between difference in erosion rate and distance from TMEM readings. A Microsoft Excel macro was developed and applied to calculate and analyse the average variation in erosion rate difference between all possible pairs of measurement readings over a set of fixed distances. The resultant analysis suggests that there are some consistent patterns between measurement periods and locations on a platform in terms of how erosion rate difference varies with distance between readings. These are not simple relationships to either characterise or explain but nevertheless, they suggest variations in how the same surface responds to erosional forces. These findings are significant for erosion research as they imply that spatial scales to erosion within even small areas may impact upon the representativeness of an average erosional loss for the platform site. It raises issues about how representative rates really are and contributes to the discussion about the wider understanding of erosion rates across spatial scale.