Far-field impact of water injection dredging in the Crouch River

Water injection dredging (WID) is a dredging technique by which the sediment to be removed is fluidised through low-pressure injection of water into the bed. Upon fluidisation, the mud flows as a density current away from the dredging site. In this paper the far-field effects of WID are evaluated—that is, the large-scale dispersion and deposition patterns of the mobilised sediments are determined. This is done with numerical simulations using a two-layered fluid mud model, which takes account of the effects of supercritical fluid mud flow, and for all mud exchange processes in the vertical direction. This model is applied to simulate a dredging work carried out in the River Crouch, UK. The agreement of the numerical results with observed patterns of dispersion and deposition is satisfactory. Next it is shown how this model can be used to evaluate alternative dredging strategies. With respect to the WID operations in the River Crouch, it is concluded that the far-field effects of the work are small.