The Continuous Measurement Of Bedload Discharge

Abstract

The Birkbeck bedload sampler is described and evaluated under field conditions. A submergedpressure-pillow responds to changes in both stream-stage and bedload sediment accumulating in apit-trap sunk into the stream-bed. Simultaneous changes in both pillow pressure and water-stageare continuously recorded. Subtraction of synchronous values gives a linear response in pressurehead proportional to the changing submerged mass of trapped sediment. Under both controlledlaboratory conditions and field installation, prototypes yield reproducible estimates of bedloadwith a standard error as small as 0.34 kg. The sampler is designed principally for installation insmall streams with flashy flood hydrographs.