Temporal soil loss scenarios and erosional dynamics of a slopping landmass in the southwestern India before and after the 2018 severe rainfall and mega flood events

The study focused on the erosional dynamics of the land adjoining the Western Ghats before and after the extreme rainfall and mega flood event in 2018. The study area is situated on the windward side of the Western Ghats in the southwestern region of the Indian subcontinent, which is renowned for its orographic rainfall patterns. To assess the temporal soil loss / temporal soil erosion (TSE), the Revised Universal Soil Loss Equation (RUSLE) was used. The variables of soil erodibility (K) and slope length and steepness (LS) were held constant, while the factors of rainfall erosivity (R) and cover management (C) were analyzed using datasets from the years 2017, 2018, and 2022 (referred to as TSE 1, TSE 2, and TSE 3, respectively). The analysis revealed the impact of the extreme rainfall event on the soil erosional characteristics of the study area. There was a noticeable variation in the rate of annual soil loss and erosion severity across the region. Notably, during the time frame of TSE 2, both the maximum value of annual soil loss (527 t. ha− 1. y− 1) and the mean soil loss (6.20 t. ha− 1. y− 1) experienced a remarkable increase compared to TSE 1 and TSE 3. Additionally, areas with high soil erosion severity witnessed a 47-fold increase, while areas with low erosion severity exhibited a significant reduction in the year 2018. However, in TSE 3, despite receiving higher rainfall, the areas with higher erosion severity displayed a reduction, indicating a re-stabilization of the terrain against erosion. The analysis also highlighted the crucial role of extreme rainfall in influencing the severity of erosion in the study area. In comparison to TSE 1, TSE 2 experienced a significant threefold increase in rainfall erosivity, reaching a peak value of 33,711 MJ mm ha− 1 h− 1 year− 1, whereas it was only 13,806 MJ mm ha− 1 h− 1 year− 1 in TSE 1. Similarly, in TSE 3, the highest erosivity of rainfall was documented at 34,901 MJ mm ha− 1 h− 1 year− 1, accompanied by a maximum annual rainfall of 4853 mm. The rise in erosivity value was primarily attributed to the intense and severe fluctuations in monthly rainfall. However, when comparing TSE 3 with TSE 2, the overall erosion was found to be decreased. These findings indicate that the severity of erosion observed in 2018 (TSE 2) was a consequence of the extreme rainfall events that occurred within a short period of time. This trend continued in subsequent years with varying severity, as the state witnessed various extreme rainfall events. While the research successfully provided insights into the spatial and temporal dynamics of erosion severity in the region, there is a growing necessity to investigate the long-term and decadal variability in rainfall erosivity in the study area. Such an investigation is essential for the formulation of effective measures to control and mitigate soil erosion in the state. Consequently, these results also emphasize the importance of implementing an effective land use policy to address the adverse impacts of the impending climate change related extreme weather events.