Various types of vegetation cover in riverine ecosystems, streams, and wetlands constitute an important component of these environments and influence their surroundings. Vegetation can play a significant role in improving water quality by reducing contaminant concentrations through adsorption and dilution processes. Therefore, this study experimentally investigated the effects of no vegetation and reed vegetation cover on pollutant transport in a laboratory flume, as well as the variation of contaminant concentration downstream of the injection point. The experiments were conducted in a rectangular channel with a length of 12 m, a width of 0.5 m, and a depth of 0.7 m. Sodium chloride (NaCl) solution was used as a tracer in the main flow, and potassium permanganate (KMnO₄) solution was used as a colored tracer to examine hyporheic exchanges in the sediment bed. In the experiments, 225 g of tracer was dissolved in 6 L of water and injected into the flow as the contaminant. Reed was used to simulate channel vegetation. The results showed that increasing the flow rate (Q) from 4 to 22.5 L/s led to an increase in the maximum hyporheic exchange length (LHZ) from 0.14 to 0.32 m, corresponding to 128%, and the mean hyporheic residence time (RT) from 290 to 584 s, corresponding to 50%. The results also showed that increasing the vegetation length (L) from 2 to 6 m caused a 15–52% reduction in residence time (RT) under different flow conditions, while in some cases the maximum hyporheic exchange length (LHZ) increased by up to 56%. These findings indicate the direct influence of vegetation length (L) in regulating hyporheic exchange and altering the pattern of flow penetration into the sediment bed.