Riparian and wetland plants have specific reproductive characteristics, growth forms and dispersal mechanisms that enable them to flourish and persist within certain conditions. Thus, assemblages of plants vary in space and time with antecedent conditions, and seasonal and annual weather patterns. This paper reports observations of groundcover vegetation responses to a range of different weather and inundation conditions experienced in semi-arid floodplains and wetlands across the Lower Lachlan Catchment NSW, Australia. Sixteen sites were monitored between 2014 to 2022, a period which encompassed vastly different weather and hydrological conditions. In the first- and fifth-year conditions were dry, with no inundation of floodplains and wetlands. The second and sixth years were wetter resulting in short-term inundation of low-lying wetlands. The third and seventh years of monitoring presented very wet conditions resulting in widespread inundation. More than 170 species were recorded over the 8-year period. Distinct annual and inter-annual temporal patterns in species assemblages were observed enabling the development of models to predict species assemblages based on inundation conditions. During dry periods, the species were dominated by terrestrial groundcover species, mainly annuals and short-lived perennial chenopods, brassicas and grasses with recent rainfall influencing interannual variation. Many of these species were also present following periods of short-term inundation but were absent following extensive flooding. Flooding produced a distinct successional response in the vegetation beginning with the appearance of aquatic and amphibious plants and transitioning through to less flood tolerant terrestrial species, with time since inundation the major factor influencing interannual variation.