Can the long-term effects of beach cleaning heavy duty machinery on aeolian sedimentary dynamics be detected by monitoring of vehicle tracks? An applied and methodological approach

Abstract

Beach-dune systems are fragile ecosystems vulnerable to changes, especially those associated to human activities. This study focuses on El Inglés beach (Canary Islands, Spain), which is located on the eastern limit of the Maspalomas dunefield. This is the sediment input to the dunefield, and vehicles that provide urban-touristic services circulate every day, most notably heavy duty machinery responsible for beach cleaning. The aim of this study is to make a first methodological approach and a quantitative and empirical analysis of the long-term environmental effects, especially on the topography and geomorphology, that mechanical beach cleaning services could have on the aeolian dynamics, using as an indicator the vehicles tracks mapping. The methodology is divided into four sections: i) a spatiotemporal study of vehicle tracks on the beach; ii) a field campaign to observe beach cleaning activities in situ and compile data; iii) an interview with the local team responsible for beach cleaning; and iv) a general analysis of the aeolian dynamics over the almost last two decades. Results shown not only a high correlation between vehicle tracks and heavy duty machinery tracks, but also the variation in vehicle track density was proven to follow changes in the management process and the number of tourists. Different track densities varied depending on the intensity of the presence of visitors and hence the intensity of beach use, which is not homogeneous throughout the beach. A study of the deflation surfaces as erosion process found that they not only remain steady but even increase in some areas with high vehicle track densities, with no sedimentary gain. Although management activities like cleaning and levelling may not have a direct impact on the dunefield, they were positively correlated to deflation surfaces, increasing sediment loss in the beach area. These activities could be leading an artificially-maintained steady beach contrary to documented sedimentary loss in the dunefield. In conclusion, the pioneer approach of analysing the vehicle traffic through tracks monitoring, especially beach cleaning activities, has shown the viability to detect long-term effects on the sedimentary dynamics, including sediment loss to the foredune and, therefore, inside the system.