ABSTRACT

The term ‘drainage’ has been used to describe all processes whereby surplus water is removed from lands. This includes both internal drainage of soils and the collection and disposal of surface runoff. Water-logged land is of little use. However, it can be utilised after providing proper drainage arrangement. Usually in undulating country, the surface slopes are sufficient to carry off this surplus water into the ditches and streams without any engineering construction. Low-lying flat areas are usually invariably near or below the flood level of the river. In order to utilise the area, the river must first be prevented from flooding it, usually by construction of flood embankment. Arrangements have then to be made to collect and dispose of the water otherwise entering the area. The area may be so low that gravity, discharge is not possible all the time. Such conditions occur in the lower reaches of a tidal river. The problem in such cases is to collect and convey the water entering the area to a discharge point and then pass it into the river either by gravity or by pumping.