Journals Proceedings

Abstract

Hydrographic networks are becoming increasingly subject to unsteady flow regimes. These may be the result of a torrential habitat or because the flow is regulated by detention structures and can result in morphological instability. In such cases, the flow (which often divides into more than one branch) may meander along the river bed close to the bank, causing local scours to the bank and to any structures built along the river. A common technical practice is to employ bottom sills in order to stabilise mobile river beds and protect them from scour. This paper analyses some experimental tests conducted on bottom sills and points out that when the stream meanders unpredictably in the river bed or when the sill is at an angle to the stream, even though this flows in a single direction, the scour phenomenon is accentuated. As a result, assessments of scour in the proximity of river management works, carried out using the empirical formulas normally adopted in technical practice, may turn out to be totally insufficient.