Modeling and managing erosion in arid ravines using high-resolution satellite imagery

Abstract

Ravines in arid lands are affected by various soil erosion processes caused by inconsistent rainfall regimes, flooding patterns, and anthropogenic interventions. These effects are expressed in the geomorphological and vegetation patterns of the ravine's land segments. To address these changes, a study was planned with the following objectives: [1] Modeling the effects of ravine erosion processes on its land-segments vegetation using high-resolution satellite imagery; [2] Suggesting analysis schemes based on remote sensing to suit land management practices for the ravine parts.  The study site is located in Migda Ravine, Northern Negev, between Gerar and Patish ephemeral streams. Due to the loess soil and extreme arid conditions, the area suffers from soil erosion and land incision. Using imaging from PlanetScope® satellite constellation (spatial resolution: 3m pixel^-1, temporal: Image per 3 days, and spectral: Red-Green-Blue-Near Infra-Red bands) between 2017 and 2024, from January to August each year, NDVI median and quartiles ranges of the ravine land segments were calculated and normalized against a stabilized reference plot. Thirteen erosion processes were defined, and classified into ravine surrounding areas, banks, and ephemeral stream water flow. The findings indicate erosional processes that dramatically decreased the Normalized Fresh Vegetation Reflectance (NFVR)in 2019, with a lighter decrease in 2020. Some erosion processes were characterized by a subsequent NFVR increase after the soil erosion event, while others, such as subsurface erosion, showed a continuous NFVR decrease. Stream plots were characterized by soil deposition, which resulted in vegetation flocculation. Using vegetation change patterns, NDVI normalization, and multi-year temporal analysis can aid in formulating land management practices for the ravine land segments and predicting long-term erosional patterns.