Remote sensing monitoring of the impact of a major mining wastewater disaster on the turbidity of the Doce River plume off the eastern Brazilian coast

Abstract In November 2015, the Doce River basin was struck with Brazil’s worst environmental disaster: the collapse of an iron ore mining waste water dam delivering about 60 Mm 3 of contaminated mud that traveled from its headwaters to the Atlantic Ocean. We analyzed the impact of the tailings dam failure on the turbidity of the Doce River plume and coastal waters based on remote sensing methods applied to Landsat and MODIS-Aqua imagery. Turbidity maps were obtained using a semi-analytical algorithm that uses a two band (i.e., red and near infrared) selection scheme to optimize the retrieval for a wide range of turbidity levels. The dam failure occurred in the context of a severe hydrological drought, but despite the abnormally low streamflow the turbidity front of the Doce River plume at the coast peaked to levels above 1000 FNU after the disaster. With subsequent rainfall-runoff events, the deposited mud within the river-estuary system continued to be washed out and cause high turbidity levels with extensive plumes over the coastal zone. The high turbidity (>20 FNU) plume front reached 11 km off the coast towards the southern shelf, the moderate turbidity plume (10–20 FNU) reached 39 km, and the low turbidity plume ( in situ stream flow and turbidity measurements allowed disentangling the impacts caused by the tailings dam failure from the natural sources of suspended sediment that influence the variability of coastal water turbidity.