ABSTRACT

Both pipes and channels are used to carry water. They are clearly different in appearance but they are also very different in how they behave hydraulically. Pipes are completely enclosed, circular in section and usually flow full of water. In contrast, channels are open to the atmosphere and can have many different shapes and sizes. Pipes can also flow uphill and downhill but open channels can only flow downhill under the influence of gravity. But pipes do sometimes flow only partly full though this is not so common. An example is when they are used for gravity flow sewers which take sewage from houses and factories into the main sewerage system. The flow in such cases only partly fills the pipes and so hydraulically they behave like open channels and not pipes. The reason pipes are used for this purpose is that sewers are usually buried below ground to avoid public health problems. It would be difficult to bury an open channel!