DGPS based methods to obtain beach cusp dimensions

Abstract

Statistical correlations between wave parameters and cusp dimensions other than spacing may provide insight into which processes intervene in beach cusps formation and evolution. However, there is little information about cusp dimensions such as cusp depth, height or elevation. The aim of this work is to evaluate and compare different methods to determine beach cusp dimensions in order to assess which one produces more accurate, extensive and easy-to-achieve results. For this purpose some beach surveys were carried out at Ofir beach, located on the Portuguese west coast. Each one of the methods uses different sampling and processing strategies to obtain beach cusp dimensions. In method 0 cusp dimensions were determined using only two tape measures. The remaining 4 methods use Differential Global Positioning System (DGPS). Methods 3 and 4 provide values for cusp spacing, height, elevation and depth whilst methods 1 and 2 provide values for the first three parameters only. If one is only interested in measuring beach cusp spacing, height and elevation, then method 1 seems to be more adequate, due to its ease in sampling and in dealing with the data processing. Values of spacing, height and elevation obtained via Method 1 are the most accurate ones. On the other hand, if one wishes to perform a more detailed analysis, including parameters other than the above-mentioned and, for instance, to produce Digital Elevation Models (DEM), a combination of Method 1 and Method 3 or 4 is more appropriate.