Soil erosion, while often studied in dryland settings for rural regions, has only occasionally been studied in urban settings. This study maps and quantifies areal extent and severity of water erosion in a dryland city (Windhoek, Namibia) using a snap-shot field survey approach. The results show that nearly 56% of the city could be affected by water erosion with signs of accelerated erosion in the form of rills and gullies. These occur mainly in the underdeveloped, informal and semi-formal areas of the city. Factors influencing the extent of erosion in Windhoek include vegetation cover and type, socio-urban factors, and to a lesser extent, slope. A comparison of an interpolated field survey erosion map with a conventional erosion assessment tool (the Universal Soil Loss Equation) highlights a mismatch in the spatial patterns found, underlining the inapplicability of traditional non-urban erosion tools to urban settings and emphasises the need to develop new erosion assessment and management methods for urban environments. Measures for controlling water erosion in the city need to be site-specific as the extent of erosion varied greatly across the city.