Aquatic macrophytes, especially Vallisneria nana, provide essential spawning, foraging and juvenile refuge habitat for the threatened Australian lungfish (Neoceratodus forsteri). Dams and weirs reduce connectivity and alter river flows, often impacting the distribution and abundance of macrophytes. Reduced connectivity can inhibit hydrochory (dispersal by water), the primary process of downstream propagule dispersal. Reduced hydrochory likely impedes the recovery of macrophyte populations after large disturbances, such as floods. We conducted annual quantitative surveys in the Brisbane River from 2020 – 2022 of two sites upstream and seven downstream of Wivenhoe Dam, to assess changes in macrophyte habitat, distribution, abundance and impacts of the catastrophic floods in early 2022. Propagules were also collected using drift nets at three sites upstream and two downstream of Wivenhoe Dam to detect propagule dispersal at base flow conditions and assess the impact of the dam. Six species of macrophytes were observed during the annual surveys at the nine study sites, with V. nana and Ottelia alismoides being the most widespread and abundant species sampled. Vallisneria nana occupied shallow to moderate depths (0.1 – 0.6m) and low water velocities (<0.2m.s-1) within a broad range of substrate types (usually mud, gravel and cobbles). Following the 2022 floods, V. nana was detected at one upstream site and no macrophytes were detected downstream of the dam. No propagules or macrophyte material were collected downstream of the dam. These results indicate that downstream macrophyte recovery following large disturbances is impeded by the barrier effect of the dam, reducing hydrochory through blocking propagule dispersal and hampering recovery post-disturbance. This reduced recovery is likely to have significant implications for spawning and recruitment of N. forsteri. Further research is required to evaluate the feasibility and efficacy of macrophyte replanting downstream of the dam to foster hydrochory and natural regeneration following severe flood events.