Rates of Overbank Sedimentation on the Floodplains of British Lowland Rivers Documented using Fallout ¹³⁷Cs

ABSTRACT

Bomb-derived fallout ¹³⁷Cs has been used as an environmental tracer to study rates of overbank sedimentation on river floodplains. The depth distributions of fallout ¹³⁷Cs in sediment cores collected from depositional sites on the floodplains of twelve lowland rivers in Britain have been employed to estimate mean annual overbank sediment deposition rates over the past 30–40 years, assuming a constant rate of sediment deposition and a correspondence between the shape of the observed ¹³⁷Cs profiles and the history of radiocaesium inputs. Values of sedimentation rate estimated for the twelve sites range from 0.11 g cm^-2 yr^-1 to 0.95 g cm^-2 yr^-1. Variations in the levels of ¹³⁷Cs activity associated with surface sediment from the individual sites can be used to interpret the dominant sediment sources in the individual catchments.

Key words:

• fallout ¹³⁷Cs
• river floodplains
• overbank sedimentation
• radionuclides