Tidal riparian zones are increasingly recognized as biogeochemical filters that mitigate nutrient loading to estuaries, yet the mechanisms controlling nitrate removal under oscillatory flow remain poorly quantified. Here we integrate one-dimensional Boussinesq-based flow modeling, reactive transport simulations, and Monte Carlo experiments to evaluate nitrate attenuation in tidal riverbanks. Results show that water table oscillations drive short but frequent infiltration–exfiltration events that create temporally discrete windows of reactivity. The near-bank margin (0–8 m) functions as a hotspot of nitrate transformation, with removal strongly coupled to tidal exchange. Sensitivity and Sobol analyses identify first-order degradation rate (λ) as the dominant control, with hydraulic conductivity and tidal amplitude modulating its effectiveness. A Damköhler framework reveals threshold behavior distinguishing transport-limited from reaction-limited regimes, while Buckingham Pi–based regression achieves high predictive skill (R² > 0.94) across diverse conditions. Monte Carlo ensembles highlight strong variability in removal potential, underscoring the need for probabilistic assessment. Collectively, this work demonstrates that tidal riparian buffers can substantially attenuate nitrate when reactivity aligns with hydrologic exchange, and it provides transferable, dimensionless tools to predict performance across coastal systems. These insights inform management strategies aimed at enhancing hydrologic connectivity and sustaining ecosystem services under changing climate and tidal regimes.