Estimates of soil erosion rates in a principal watershed in Gozo, Malta under current and future climatic conditions

Abstract

The aim of the study was to estimate the current and future annual soil erosion rate in the Ramla watershed situated in Gozo, Malta. The RUSLE-GIS was applied using innovative approaches, such as the inclusion of the highest possible DEM data as well as reflecting climatic changes to the R Factor based on the latest climate projections for Gozo derived from a total of eight CMIP6 climate change models. A climate change impact analysis was carried to estimate the likely future risk of soil erosion in this local watershed for the first time. The estimated annual soil loss, as a percentage of the total area of study varies from low (85.1%), to moderate (13.3%) and high (1.6%). Within a climate change context, a reduction in the annual soil erosion rate has been estimated for the period 2080–2100, ranging from −5 ton ha−1 yr−1 under SSP126 to −6 ton ha−1 hr-1 under SSP585. The estimated decrease of annual soil loss within the high soil erosion risk category is attributed to an increased aridity of the local climate as projected by eight CMIP6 climate models. Specific hydrological sub-watersheds were identified within the study area that warrant urgent considerations. The outcomes of this study are based on the inclusion of micro-topographical information derived from high resolution 1 m LiDAR DEM. This modelling work is seen as the first study which can be used to provide some objective guidance on the minimization of potential soil losses within the Ramla watershed. Our estimated soil loss and its spatial distribution can assist in a fuller management plan for the sustainability of this watershed. These results should not be interpreted in absolute terms but as an understanding of the underlying controlling processes, the relative spatial and temporal variations, and of possible future scenarios.