The risk of erosion and desertification is a major problem in the Mediterranean region in general and Algeria in particular. Algeria has a known downward trend of very high rainfall since 1975, especially in the Central and Western regions. In this work, the spatial pattern and temporal trend of the modified Fournier index (MFI) are investigated. Also, it is aimed to answer the question of whether a change has occurred or not in the concentration of rainfall using the precipitation concentration index (PCI). A total of 117 rainfall stations are used to determine these two indices as well as the development of a formula for calculating MFI based on annual rainfall. For mapping the modified Fournier index, 273 stations are used. The results show no change in the seasonal distribution of rainfall. However, a downward trend of about 30% of MFI is present in the Central and Western regions. The eastern regions of the North Algeria have not experienced this decline. The spatial variability shows that the MFI value increases from the west to east and from the south to north.
Keywords: rainfall erosivity, modified Fournier index, MFI, regionalisation, mapping, North of Algeria