The Asian elephant (Elephas maximus) faces severe anthropogenic habitat fragmentation across South Asia, where terrestrial land-use conversions strictly preclude the gazetting of expansive continuous terrestrial protected reserves. In such human-dominated multi-use matrices, natural riparian river networks represent critical, topographically unconstrained microhabitats that simultaneously provide foraging resources, perennial water, and low-resistance movement pathways. We conducted an empirical investigation across 820 contiguous 1-km reach units along 11 major tributary networks of the Brahmaputra River in the North Bank Brahmaputra Landscape (NBBR) of Assam, Northeast India. A dual-detection survey protocol (combining standardized pedestrian sign searches with structured key-informant interviews across 500-m reach buffers) yielded an empirical detection probability of p = 0.82 and documented elephant presence across 429 reaches (naive occupancy = 52.3%). Generalized Linear Mixed-effects Models (GLMM; marginal R² = 0.67, conditional R² = 0.94) with river basin as a random intercept revealed that elephant riverine site-use was strongly favored in upper foothill entry reaches (β = +3.83 ± 0.46, P < 0.001; Odds Ratio [OR] = 46.19) and river channels with high discharge volume (β = +0.47 ± 0.19, P = 0.015; OR = 1.60). Proximity to matrix land covers—specifically commercial tea plantation agroforests (β = -2.17 ± 0.28, P < 0.001; OR = 0.11), alluvial grasslands (β = -1.16 ± 0.28, P < 0.001; OR = 0.31), and protected forest reserves (β = -1.43 ± 0.48, P = 0.002; OR = 0.24)—substantially elevated site-use odds, underscoring that tea estate shade canopies serve as vital diurnal stepping-stone refuges. Conversely, low-clearance transport infrastructure (< 4.5 m vertical underpass clearance) exerted severe negative deterrence (β = +1.60 ± 0.30, P < 0.001; OR = 4.97), compressing channels and deflecting moving herds into agrarian settlements. Spatial projection of the parameterized model across 9,679 regional river segments in 30 drainage basins identified 5,674 functional corridor reaches (ROC AUC = 0.93; 5-fold cross-validation AUC = 0.875). Continuous corridors connecting > 1,200 km² of core foothill reserves were identified along the Jia-Bharali, Bargang, and Buroi rivers. We propose three actionable interventions: mandatory bridge underpass clearances (≥ 5.5 m vertical height, ≥ 30 m horizontal span), statutory gazetting of 1-km riparian buffers, and formal tea estate agroforestry partnerships to secure megaherbivore gene flow and promote sustainable human-elephant coexistence.