Soil erosion resistivity metric for sub-watershed prioritization

Abstract

Soil erosion is a critical factor in soil and water degradation, necessitating the implementation of effective watershed management strategies to mitigate these impacts. Even with its worldwide importance, little is known about the temporal and spatial pattern of soil erosion, which hinders the creation of focused mitigation strategies. In this regard, this study introduces soil erosion resistivity, a novel metric that assesses temporal stability using the normalized coefficient of variation, to prioritize sub-watersheds in Iran's Shazand Watershed, employing the Revised Universal Soil Loss Equation (RUSLE). Resistivity classified sub-watersheds into five stability categories, including unstable (0.81-1), relatively unstable (0.61-0.8), moderately stable (0.41-0.60), relatively stable (0.21-0.4), and stable (0-0.2). Results showed a declining trend in overall erosion, with a sharp increase in 2018 attributed to extreme rainfall. The mean annual soil erosion was 14.94 t ha^-1 y^-1, with sub-watersheds 15 and 9 identified as the highest priority for management. Whereas sub-watersheds 5, 6, and 7 were classified as the lowest priority. In contrast, resistivity-based prioritization revealed critical nuances, as sub-watershed 11 (19.07 t ha^-1 y^-1, relatively unstable) ranked as the highest priority. At the same time, higher-erosion areas (e.g., sub-watersheds 9 and 15) were moderately stable and classified as a secondary priority. Sub-watersheds 2, 18, and 23 also showed statistically significant declines. Unlike conventional soil erosion rate-based approaches, resistivity highlights areas with persistently high erosion, enabling precise conservation targeting. These findings underscore the importance of adopting sustainable practices and prioritizing management efforts in vulnerable regions to effectively mitigate soil erosion.

Keywords: Integrated watershed management; Soil conservation; Spatiotemporal variation; Watershed prioritization.