Soil erosion in Binġemma-San Blas valley : a multiscale and multitemporal approach

Abstract

Accelerated soil erosion is a global issue which directly and indirectly impacts the surrounding environment in various ways. In the Mediterranean region, soil erosion is typically more severe. Therefore, this study aimed to estimate the total annual soil loss in the San Blas and Binġemma valley, a small watershed in Gozo, Malta using the RUSLE equation, at two different spatial resolutions. The use of two spatial resolutions was to determine if a coarse 30 m DEM could be used if a finer DEM was unavailable. Through comparison between soil loss estimates obtained from ASTER GDEM and LiDAR-derived DEM of 30 m and 1 m spatial resolution respectively, it was determined that while ASTER GDEM tends to overestimate, the positive correlation between the two datasets is very strong and despite their slight difference, ASTER GDEM can be used to obtain soil loss estimates over the valley, especially to determine hotspot areas of high soil erosion values. Another aim was to estimate historical soil losses in the same valley. The estimates cover a period between 1957 and 2021 with approximately 10-year intervals. Future soil loss predictions for 2050 under SSP 2-4.5 and SSP 5-8.5 were also estimated using precipitation data from CMIP6. Findings showed that mean past estimates fluctuated slightly but had a decreasing trend, with means ranging between 2-7 t/ha/yr in all the past years estimated. Future soil loss predictions were found to be lower, especially for SSP 5-8.5 which had a mean soil loss of 0.87 t/ha/yr.