Analysis of seasonal environmental fragility using the normalized difference vegetation index (NDVI) and soil loss estimation in the Urutu watershed, Brazil

The intensification of land use has contributed to the emergence of environmental impacts such as soil loss, silting of water bodies, and reduction of biodiversity, among others. Using models capable of seasonally diagnosing environmental damage is essential in territorial planning and management, demonstrating the spatial distribution of the environment’s sensitivity to developing erosion processes and quantitatively valuing soil loss. Thus, assuming a significant relationship exists between the seasonal variation in environmental fragility and the validated estimate of soil loss, reflecting the conservation status of the river basin. Therefore, this work aims to analyze the seasonal Environmental Fragility (EF) from the autumn of 2019 to the summer of 2020 using the soil loss estimate. Data such as slope, erodibility, erosivity, and the normalized difference vegetation index (NDVI) were used to achieve this. Statistical tests were also applied to assess the significance level of the models in the seasonal evaluation and the validation based on ground truth points. The results showed seasonal differentiation in the EF and the soil loss estimation. Spring was the one that resulted in the most extensive area classified as high EF (27%) and with an estimated soil loss of 0.3733 t.ha-1month-3. The summer presented the highest soil loss estimation with an average value of 0.4393 t.ha -1month-3. Autumn (0.07683 t.ha-1 month-3) and winter (0.0569 t.ha-1 month-3) showed the lowest rates of soil loss, and the most prominent areas were classified in the low class of EF, as a result, mainly of the erosivity of the rains. The results indicated by the seasonal models of EF and soil loss were validated through erosion points using spatial statistics tests.