The Amazon is the largest tropical forest in the world, covering more than 7 million km². This biome holds the largest hydrographic reserve, accounting for 16% of the planet's freshwater. However, Amazonian rivers are threatened by the expansion of illegal gold mining, which pollutes the water bodies with heavy metals and causes changes in fluvial morphology. Ecuador has 120,000 km² of Amazon biome, where at least 1,660 ha have been deforested by illegal gold mining in rivers such as Nangaritza, Zamora, Yutzupino, Jatunyacu, and Punino. This study aimed to calculate geomorphometric parameters over the Punino river channel to assess the impact of illegal gold mining expansion on fluvial morphology, using Sentinel-2 imagery and supervised classification. The methodology was based on three stages: i) the collection and processing of annual satellite image mosaics (2019 and 2023), ii) Land Use and Land Cover Classification (LULC) using Random Forest, and iii) calculation of morphometric parameters. The results revealed that, in 2019, 28.44% of the channels were choppy and 17.43% were sinuous, representing discontinuities in the Punino River. Meanwhile, in 2023, 37.61% of the channels were meandering and only 17.43% were choppy, suggesting an increase in the flow and continuity of the water body. In addition, in these 4 years, an increase in the measured circularity radius of 87.96% of all meanders analysed was recorded. This impact on the fluvial morphology of the Punino River is associated with the expansion of 217 hectares of mining land and the increase in turbid water in 315 hectares. This paper proposes a methodology based on the use of remote sensing, geoprocessing, and river geo-morphometry techniques to assess the impact of illegal gold mining on Amazonian rivers.