Lateral sediment connectivity and hydrosedimentological modeling in a large tropical watershed: A spatial correlation analysis

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Abstract
Soil erosion and sediment transport are significant environmental problems in watersheds, with direct impacts on water quality, channel siltation, and the service life of reservoirs. The concept of sediment connectivity has become established as a complementary approach to mathematical modeling for understanding sediment dynamics, although its integration with hydrosedimentological models in large tropical watersheds remains in its infancy. This study evaluated the correlation between the results of the MGB-SED model and the lateral connectivity index developed by Borselli et al. (2008) in the Doce River watershed, Brazil. The MGB-SED model, calibrated for the period 1998–2014, demonstrated good performance for discharge and sediment yield. The estimated average annual sediment production was 1.55 × 10 7 t/yr, with the highest values concentrated in the Piracicaba, Caratinga, Suaçuí Grande, and Santo Antônio river basins, associated with mountainous terrain and the prevalence of degraded pastures. The lateral connectivity index ranged from −11.98 to 1.99, with higher values in the dissected plateaus of the central south and lower values in the Rio Doce Depression and the Espinhaço Mountains. The Spearman correlation between the IC and the MGB-SED variables was low for all metrics evaluated (ρ ≤ 0.165), which is attributed mainly to the distinct nature of the two models: the IC considers exclusively structural aspects, whereas the MGB-SED incorporates functional components. The results indicate the need to develop connectivity indices that incorporate functional components, especially for large basins in humid tropical environments.

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