Ephemeral rivers are a particular type of dryland river which only flow during and immediately after rain events. Despite their important social and ecological roles in drylands we know very little about the ecosystems or their sensitivity to human activities. This PhD investigates drivers of riparian tree distribution, recruitment and dieback along a dammed ephemeral river; and also investigates wider changes that have occurred to the riparian ecosystem and stakeholders’ perceptions of these changes. A variety of methods are used such as ecological and social surveys, remote sensing and archival searches. The study system is the Swakop River in Namibia; the largest catchment of the country’s westerly flowing ephemeral rivers. In the 1970s two large dams were installed in the upper catchment of the river to supply water to central Namibia, including the capital city of Windhoek. In order of abundance, the riparian woody vegetation community of the Swakop River is composed of Prosopis species (an invasive species introduced in the 1900s), Tamarix usneoides, Faidherbia albida, Salvadora persica, Vachellia erioloba, Euclea pseudebenus and Vachellia tortilis. Although no net change in woodland extent is observed, the woodlands decreased in density by 18%. This reduction in density is consistent with the considerable mortality observed in the riparian trees: 51% of all F. albida, 29% of V. tortilis, 26% of Prosopis spp., 25% of E. pseudebenus and 23% of V. erioloba. The river’s longitudinal profile from the interior of Namibia towards the coast is associated with an increasingly drier climate. This climatic gradient is the most consistently implicated driver of riparian tree occurrence, recruitment and dieback. This study also indicates that tributaries may play an important role in tree population dynamics along ephemeral rivers and may help mitigate the negative effects of damming.