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Civil and Environmental Engineering | Engineering
Fine sediment plays a key role in the transport of contaminants in rivers and the quantification of suspended sediment flux is important to understanding and managing river catchments in the context of the EU Water Framework Directive (2000/60/EC). Recent European studies identified Ireland as having a paucity of sediment and sediment associated pollutant concentration and flux data. This paper presents the results of a continuous monitoring programme on a small scale catchment (105 km2 ) in Ireland, the River Owenabue, which is located in the South Western River Basin District. Analysis was undertaken to determine event based fluxes and their contribution to the annual flux. The continuous monitoring programme commenced in September 2009. Analysis shows that turbidity is an accurate surrogate for suspended sediment concentration for this river and when coupled to river flow data provides estimates of the suspended sediment flux. The objective of this paper is to quantify the suspended sediment flux of a small Irish River, and to analyse the dynamic delivery sequence of storm based events. The variation of the suspended sediment flux at different temporal scales is investigated and found to be significant. The annual suspended sediment flux was found to be 2635 tonnes (t) which equates to a suspended sediment yield of 25.6 t km-2 year-1. The flux analysis reveals that 85% of the total annual flux is transported over 10% of the year and 69% of the flux over 5% of the year. For one event in November 2009 with a return period flow rate of approximately 10 years, the flux is estimated at 38% of the annual flux. Hysteresis is observed and analysed for the identified events and it is found that clockwise hysteric loop are most common implying that suspended sediment transport is most commonly limited by sediment supply.
Harrington, J.R. and Harrington, S.T., ‘The influence of storm based events on the suspended sediment flux in a small scale river catchment in Ireland’, In: Monitoring, Stimulation, Prevention and Remediation of Dense and Debris Flows IV, WIT Press.