Understanding soil erosion patterns in San Blas and Binġemma valley

Abstract

Soil erosion is an increasing issue worldwide, including in Malta. Therefore one of the aims of this study was to estimate the soil loss occurring in the San Blas and Binġemma valley situated in Gozo. This was done through the use of the RUSLE equation and the use of GIS software as well as through fieldwork, high resolution DEM data and soil analysis, involving soil texture testing and organic matter testing to ensure accuracy of Lang’s 1960 soil map. Another aim was to determine the extent of the impact of the RUSLE’s C-factor, i.e. crop cover, in influencing soil erosion in the San Blas and Binġemma valley. This was done by using the RUSLE equation for 1957 and comparing it with the current RUSLE and noting how changes in soil losses change with land abandonment and land uses. This was achieved through orthophoto-interpretation of 1957 aerial photos of the area. Findings show that in 1957 erosion was more widespread but less severe. Findings also show limited erosion in most areas with values less than 5 t/ha/yr and 2 t/ha/yr in 2021 and 1957 respectively. Areas more at risk are also highlighted with the highest-prone areas shown to be along the valley floor in the middle of the valley, with erosion values reaching 13 t/ha/yr in 2021 and 5.5 t/ha/yr in 1957. When comparing the RUSLE with the individual factors, a link can be seen between the C-factor and the final map showing that areas under crop cultivation are more at risk than abandoned areas. Since erosion is seen to be increasing in magnitude in the valley, this study recommends terrace and rubble wall maintenance as well as encouragement for farmers to practice other support factors which limit erosion such as crop rotation, conservation tillage, contour planting and strip cropping. It is also recommended to perform similar studies on other valleys to determine the best course of action on a case by case basis.