Artificial Drainage Induced Erosion: The Case of Railway Culverts on the Kwezana Ridge, Near Alice, Eastern Cape

The geomorphic impacts of artificial drainage in the form of railway culverts are examined on a steep hillslope at Kwezana near Alice, Eastern Cape. An insight into the erosion and surface hydrological conditions of the hillslope at the pre- and post- railway construction stages is gained by analysing aerial photographs of the area and field surveys. Runoff concentration through a series of railway culverts induces dramatic incision of ephemeral stream channels. Field surveys indicate that no appropriate measures were taken to prevent the scour of the channels at the culvert outlets. Instability of the entire hillslope triggered by the tremendous channel incision is envisaged. Gullying has spread laterally from the channel sidewalls into the overgrazed banks and abandoned cultivated fields. The implications of this for rural land use are manifest in the shift from cultivation on the lower gentle slopes to the upper steep ones. Measures to curb the escalating erosion problem are imperative.