FRACTAL ANALYSIS OF KOSI, GANDAK AND BAGHMATI RIVER

Abstract:

Scale issues are present in all the geophysical processes. In understanding the river morphology too there is wide scale gap from coarse topography scale to fine micro scale. In the study presented here the fractal dimension of the rivers Kosi, Gandak and Baghmati are analyzed to understand the scaling attributes of their respective morphometric features.

Kosi is a major tributary of the Ganga system and is notorious for its vulnerability to frequent avulsions that inevitably lead to its shifting course. These destructive episodes have also earned the river its sobriquet of ‘Sorrow of Bihar’. Gandak and Baghmati are two sister river systems that, like Kosi, also rise in Nepal Himalayas and flow into the North Bihar Plains of India. While Gandak outfalls directly into river Ganga near Hajipur, Baghmati is a tributary river of Kosi and joins the latter near Khormaghat. It is indeed noteworthy that heavy silt laden discharges are a distinctive feature of all these rivers but the latter two (i.e. Baghmati and Gandak) do not show any definite proclivity to morphological avulsion and accompanying course instability. The seemingly distinctive morphological dynamics of Kosi is clearly seen to be at odds with the morphological regime of Baghmati and Gandak.

LANDSAT 8 imageries (USGS) are used to estimate the fractal dimensions of the three rivers using the box counting technique. The analysis of the fractal study done here shows multifractal behavior in all the three rivers. However, the fractal dimensions of Kosi River are found to be in contrast with its sister rivers which elucidate the curious behavior of the River.