Experimental observations of salt purging in a model sea outfall diffuser with eight soffit connected risers

Improved rehabilitation design for the long-term hydraulic function of mari ne outfalls with soffit connected risers is the main aim of the research pr ogramme reported here. As a step towards this goal a better understanding o f the processes of saline intrusion and saltwater purging has been develope d from detailed laboratory studies. Unsteady flow cycles have been investig ated and observed riser purging sequences have been compared against theore tical criteria. From the monitoring of riser flow salinity, quantitative me asures of the salt wedge front entrainment process have been obtained toget her with indicative figures for salt wedge expulsion rate. This interim out come is intended to alert the designer and operator of outfalls of the pote ntial problems with soffit connected riser systems. (C) 1998 Published by E lsevier Science Ltd. All rights reserved.