A frequent drainage pattern in mountainous and hilly areas is what may be called herringbone or rib pattern. If the bounding slopes of a valley are fairly steep they generate parallel tributaries which join the main or axial stream of the valley almost at right angles.

The tributary streams are rarely allowed to bend downstream to form acute-angle confluence. The pattern, therefore, is characteristically ‘herringbone’. A striking example of such pattern is provided by the Vale of Kashmir where the trunk stream, the Jhelum, is joined by tributaries transversely particularly from the southern steep slopes of the Pir Panjal Range.

Such pattern characterizes not only the Vale of Kashmir which is a tectonic valley but also the Tamar Kosi, an eastern tributary of the Kosi, the upper Rapti, a tributary of the Ghaghara, another Rapti as eastern tributary of the Gandak. The latter two valleys occur between the Lesser Himalayas and the Shiwalik Ranges and may be tectonic valleys. Herringbone pattern also occurs in the Himalayan E-W trenches (probably faults), e.g., the Upper Indus all along its course up to Hazara, the Shyok valley, a tributary of the Indus, and the Tsangpo.