The floodplain herbaceous vegetation of the Parana River (Argentina) was destroyed by a catastrophic extraordinary flood in 1982-83. The main communities were Panicum prionitis tall grasslands. According to a succession model, they were seral communities that would have evolved to hygrophilous forest. After the flood, the area was surveyed in 1984, 1988 and 2002 and analyzed with numerical methods. First, the area was invaded by a community of annual species, which were the sparse species of tall grasslands, but five years after the colonization this community disappeared and was replaced by the original tall grasslands and turfs. The tall grasslands rapid recovery and the absence of woody species support the hypothesis that this community is a stable community which was rejuvenated by catastrophic floods and was prevented to develop into woody species communities.