Stream a body of flowing water in a natural water course, containing water for at least a part of the year, and encompassing all scales, from a small rivulet to a large river.
A classification of stream according to their position in the drainage network is the stream order. A first order stream is the smallest unbranched tributary. A second order stream has only first order tributaries. A third order stream has only first and second order tributaries; and so forth. Streams may be classified in terms of flowing time; they are ephemeral (temporal flow) like the kumar, intermittent or seasonal (seasonal flow) eg the old brahmaputra, and perennial (continuous flow) like the mighty jamuna.
Genetic classification of stream is based on the age or development stage of the stream - youthful, mature and old. Youthful implies the initial state of streams. It is generally V-shaped and drains its basin imperfectly. In the case of mature streams, the drainage become more perfect; the river valleys are wide; slopes are flat; and bank erosion rate is high. The old stage is characterised by greater width, low relief and flattened stream gradient. Natural levees form along the stream bank. Most of the rivers of Bangladesh are at the old stage, eg padma and meghna. The karnafuli and halda flowing through chittagong hill tracts (CHT) and the chittagong area are also at a mature and old stage. There are some small hilly streams, eg waggachhari in CHT region, which have gained their youthful, mature, and old stages within this country.
Rivers or streams can also be classified in terms of channel pattern; they are straight, meandering, braided or some combinations of these. A truly straight channel is rare in nature. A meandering stream is one that consists of alternating bends, giving a s-shaped appearance. There are lots of meandering rivers in Bangladesh; especially the rivers of barind tract area have these characteristics. The kobadak, karatoya, ichamati, nagar and gorai are ideal examples of meander rivers. A braided stream passes through multiple channels separated from each other by bars. It is characterised by a steep, shallow course, is generally wide, and has poorly defined and unstable banks. The Jamuna, Brahmaputra, Ganges and Padma are some of the braided rivers of the country. Among those the mighty Jamuna represents the ideal type.
Three major rivers- the Ganges, the Brahmaputra and the Meghna- together with their numerous tributaries and distributaries form the network of river systems in Bangladesh. The Brahmaputra is a braided river. Most rivers of the country are meandering eg the Ganges, Meghna, Gorai and gumti. The Padma has a relatively straight reach. Coastal and other inland rivers also show combination of braided and meandering channel platforms. [HS Mozaddad Faruque]
See map in river.