CHAPTER 9 - SUBMERGED ORIFICES

2. Advantages and Disadvantages

Submerged orifices conserve head and are used where fall is insufficient for weirs. Submerged orifices can be used where cost, space limitations, or other site conditions do not justify a weir or flume. A disadvantage of the submerged orifice is that accumulations of submerged debris or sand and sediment upstream from the orifice may prevent accurate measurements. Severe blockage with trash could cause upstream bank overtopping. Where fall is not limited and space is available, a long-throated flume should ordinarily be chosen. Both weirs and flumes are less susceptible to interference from weeds and trash, and clogging is easily visible. Typically, sharp-crested weirs and some long-throated flumes are less expensive and more accurate.