Gully Form and Development on Karoo Sediments in Central Zimbabwe: A Preliminary Survey

About one tenth of Zimbabwe is characterized by sodic soils which are especially prone to sheetwash erosion and gullying associated with subsurface piping (Wendelaar, 1976). Although localized patches of sodic soil occur in poorly drained sites on granitic rocks, they are more widespread on Karoo sediments in the north-western, western and central parts of the country (see inset in Fig. 1). Previous research on these soils has been directed mainly at the dynamics of plant-habitat relationships, as a basis for devising suitable methods of reclamation (Dye, 1979; Dye and Walker, 1980), and at the definition of factors influencing the morphology and extension of headcuts (Stocking, 1977 and 1981). Consequently, a great deal is known already about the nature and current rates of erosion on sodic soils. However, very little basic geomorphological research has been carried out on the development and environmental significance of gully systems on the Karoo sediments or, more specifically, the fine sandy colluvium overlying these sediments