This study investigates the seismic site classes and characteristic site periods of bridge locations along the Madhura River which flows through rural Silchar. Silchar is a region with a history of significant earthquake damage and is located in seismic zone V. Recognizing that intensity of ground shaking is greatly influenced by shear wave velocity and is a primary seismic hazard, this study estimates the average shear wave velocity ( \(V_{{\text{s}}}^{30}\) ) values from borehole data at multiple bridge locations. These values are then used to classify the sites according to the NEHRP standard and also determine characteristic site periods. Results reveal varying site classes across the locations, with the bridge between Jangalgram and Durganagar identified as particularly vulnerable to resonance during future earthquakes. The bridge location between Jangalgram and Durganagar has a site class (D) and characteristic site period of 0.21–0.32 s which aligns with the typical fundamental natural period of bridges (0.30–1.2 s). This finding highlights the importance of considering site-specific seismic characteristics in bridge design to mitigate potential risks to infrastructure and human life in seismically active regions.