Design of sewers to control sediment problems

The need for sewers to transport sediment has long been recognised, with the inclusion in hydraulic design criteria of empirical approaches to achieve the required sediment movement. Normally, this is expressed as the requirement for a particular velocity under certain flow conditions. However, in recent years a range of research and design studies have shown that a single minimum velocity, which is unrelated to the characteristics and concentration of the sediment or to other aspects of the hydraulic behaviour of the sewer, does not realistically represent the ability of sewer flows to transport sediment. This publication details the development of a standard methodology for the hydraulic design of sewers and to produce appropriate guidance for design engineers.