On Flow-Altering Countermeasures for Scour at Vertical-Wall Abutment

Abstract

Results are presented for clear-water scour experiments at a vertical-wall abutment where the obstacle was modified with slots or roughening elements as flow-altering countermeasures against the erosion process. The laboratory campaign comprehended: a first experiment with unprotected obstacle; two experiments with slots above and beneath the non-scoured bed level, respectively; one experiment with a roughened abutment. Repeatability of the experiments was checked and was found satisfactory. The measured data set consisted of (i) scour depth with time; (ii) geometry of the erosion hole; and (iii) sediment motion pattern at several evolution stages of the process. The novel feature of the work was the attempt to combine the evidences on scour depth and those on sediment motion, with the purpose of shedding light onto the mechanism of the scour reduction by the tested countermeasures. It was argued that such strategy might furnish guidelines for following extensive investigations of scour countermeasures, aimed at finding optimal design solutions.