The morphology of the Kakumbi concave bank bench on Luangwa river
Karabassis, Edith Ngosa
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The study investigates the formation and development of concave bank benches on the Luangwa River in Eastern Zambia. The Kakumbi concave bank bench is studied in greater detail than the other two benches because of its accessibility and some of its interesting characteristics.The morphology and internal characteristics of the Kakumbi bench are studied from detailed field observations and from small format photographs showing its internal structure. Its development is mapped and traced from topographical maps and time sequential aerial photographs between 1956 and 1982. The physical character of the bench is also determined from the analysis of particle sizes of sediment samples collected in the field.The results of the analysis show that the bench consists of very fine sand which were deposited in a low flow environment with stream velocity less that 0.3m/s. This observation is consistent with the squamish and Barwon benches in Canada and Australia.The study concludes that the development of a flow separation zone on the concave bank of the Kakumbi meander has resulted in the accumulation of sediments during bankful discharge and the subsequent development of the bench. This has provided the mechanism for reversing the process of channel migration.
- Natural Sciences