According to the results of many studies construction of dams, their decommissioning, and sediment flushing from the reservoir have been associated with vegetation dynamics. However, factors governing the spatial changes of forestation in the floodplain below the dams have not been explored extensively. This study examined the interacting effects of dam, inflow and land-use patterns of catchment areas and other factors on downstream vegetation patterns along the downstream reaches of Southern African Rivers. A total of 105 segments of 15 rivers (16 dams) located in seven Southern African countries were studied. Areas of herbaceous and forest vegetation of river channels below a dam and land-use catchment area patterns were obtained by the Google area calculator and aerial image analysis. Forest development was the highest just below the dams, and the ratio of forest cover decreased with distance from the dam toward the river mouth. Forest coverage ratio was found to decrease with an increase in dyke distance, number as well as of inflows (r = -0.66, P <0.01) and water coverage ratio, and bare land in the river flood plain. However, a principal component analysis (PCA) showed that the proportion of bare land in the catchment area, the dyke distance of the river and the number of inflows or tributaries are the factors most associated with forestation among the studied parameters. Forestation progressively decreased following the entrance of free following tributaries below dams, which appeared to reduce the effects produced by dams on vegetation forestation by causing local deviation. The impact of different land use types, such as agriculture on forestation, was insignificant though in some cases, land use areas cause the forest area reduction.