Mahmoud Mahmoud - Assist. Professor, Aburayan cumpus, Tehran university, Tehran, Iran

A culvert does not necessarily flow full when the entrance is submerged unless the entrance is of a special design which allows this to happen. Normally, because of separation of the water from the sides and the top of the entrance section the entrance may act as a sluice. However under suitable conditions, the culvert may prime itself automatically. If the point at which the culvert first becomes full is called the section of priming, three distinct types of self-priming action may occur. In a model it should be determined at which discharge the barrel of a culvert can run full. The discharge, at which the barrel back to part-full flow is defined as de-priming discharge, is necessary for a computer model. The criteria which are discussed in this paper assist to distinguish between full flow and free flow in a developed computer model for complex culverts by Mashal and Ball (1998)

culvert, priming, modeling, river engineering