The time-dependent bridge pier scour during ﬂood waves is analysed. Scour experiments were conducted in a novel installation able to produce complex hydrographs with high precision. Experimental data were used to test scour formulas including a new mathematical model. Results conﬁrm the reliability and superior performance of the proposed dimensionless, eﬀective ﬂow work based model under steady and unsteady hydraulic conditions. Analyses highlight the impact of diﬀerent hydrographs on scour, demonstrating the strong control by the hydrograph shape of the temporal evolution of scour depth and scour rate, although ﬁnal scour after a ﬂood only depends on the total eﬀective ﬂow work exerted by the hydrograph on the sediment bed. Hysteresis between ﬂow discharge and scour rate is reported and explained. Flow acceleration is shown to play a minor role in scouring. The proposed model is a promising alternative for computation of local scour under highly unsteady hydraulic conditions.
How to cite: Link, O., C. Castillo, A. Pizarro, A. Rojas, C. Escauriaza, B. Ettmer, S. Manfreda, A Model for Local scour during Flood Waves, Journal of Hydraulic Research, 55(3), 310-323, (doi: 10.1080/00221686.2016.1252802), 2016. [pdf]