Mohammad Tabatabai - Assistant Professor at Power and Water Iinstifirteo f Technology, Tehran, Iran
Richard Hey - Associate professor (Reader) at university of East Anglia , School of Environmental Sciences, University of East Anglia, Norwich, UK

Although rivers experience a range dilows, it has been suggested that, over a period of years, they adjust their overall shape and dimensions to a single dominant, channel forming, flow and that this steady flow produces the same regime dimensions as the natural sequence of events. If this is the case, and provided the flow can be identified, it directly determines the design discharge for stable channel design. Alternatively, if the frequency or exceedance duration dthe dominant discharge could be established, then this would enable the design discharge to be indirectly determined, possibly without the need for field measurements. In this review the authors have assessed two methods to determine the dominant channel forming discharge: 1 -direct determi.nation of the dominant discharge by uing banhll and effective discharges, 2-indirect determination of the dominant discharge by using the frequency and duration of the bankfull and eEectice discharges, respectively.