Fluvio-geomorphic hazards encompass the destructive interactions between fluvial processes—water flow and sediment transport—and human settlements. This study analyzes the hazard continuum within the Digaru River basin of the Eastern Himalayas, a region defined by tectonic instability and intense monsoonal rainfall. Utilizing a 49-year longitudinal framework (1966–2015) supported by satellite imagery and GIS modeling, the research explores the critical nexus between upstream mass wasting and downstream hydrological volatility. Findings reveal that the upper catchment acts as a significant sediment source; despite localized afforestation efforts, recent anthropogenic interventions like road construction have exacerbated landslide activity, impacting nearly 10% of the basin. This sediment influx leads to riverbed aggradation in the plains, transforming the river into a braided, erratic system—locally termed “Pagla Nadi”—characterized by frequent avulsions and aggressive bank erosion. Approximately 25% of the lower basin is classified as a high-risk flood zone, where “unproductive siltation” perennially degrades agricultural viability. These dynamics trap riparian communities in a state of “hydrological poverty,” characterized by chronic displacement and non-resilient infrastructure. The study concludes that traditional “hard” engineering solutions are largely ineffective in such dynamic environments. Instead, it advocates for a multi-scalar management approach that integrates highland bio-engineering with resilient lowland infrastructure and enhanced socio-economic support systems to mitigate the impacts of the region’s evolving geomorphic rhythms.