Fractionation and measurements of settling velocities of suspended matter using an owen tube

In June 1993 an intercomparison programme was carried out in the zone of maximum turbidity of the Elbe estuary. A number of methods for characterizing estuarine floc size and measuring the settling velocity of suspended matter were compared. This study presents data of field measurements obtained with an Owen settling tube of the type Braystoke SK 110. Differences in the results (median settling velocities, concentration of suspended particulate matter) of the various types of settling tubes are discussed. They are considered to be dependent on SPM patchiness and on handling of the instruments. The content of organic material in flocs increases towards the slower settling fractions. Alternative uses of the Owen tube are discussed.