The Ganga Morphology - The Ganga: Water Use in the Indian Subcontinent - page 34

Chapter 5
The Ganga Morphology
The Himalayan ranges from where the Ganga and its northern tributaries originate,
are still young and friable. Frequency of earthquakes owing to tectonic changes in
the region and heavy rains in the catchments owing to elevation, spread and direction
of the ranges obstructing the monsoon wind, cause frequent landslides and erode the
soil. Variations of extreme temperature and the friable nature of the rocks enhance
silt deposits. All these lead to high silt charge in the Ganga and its northern tribu-
taries. As against this, non-Himalayan rivers, flowing south of the Ganga sub-basin
originate at much lower heights and in lower rainfall zones. They drain the regions
which are geologically more stable and carry much less silt and therefore, have a
more stable course than the Himalayan rivers.
As stated, the Ganga takes its name not from the origin in Gomukh in the
Himalayas but from Devaprayag where the Alakananda and the Bhagirathi join.
Its source is at an elevation of 7,010 m, from where it flows nearly 280 km before
descending on the plains at Rishikesh. Haridwar is 30 km downstream, from where
it flows southward over a wide bed of boulders, with its volume of water much
diminished when it enters the Upper Ganga Canal at Mayapur on the right bank
in Saharanpur district. Southward, its bed becomes sandy, depositing alluvium on
the banks. The Ganga flows shallow and unfit for navigation until it reaches Nangal
in Bijnor district of UP, from where it takes a wide sweep first southwest and then
straight south from Balawali rail bridge. Field observations revealed that the river's
course in this zone shifted westward for about 1 1 / 2 km from its former course. For
several kilometres beyond Daranagar village, the Ganga flows almost straight south;
presently, it is moving eastward from the village, severely eroding the right bank
(Fig. 5.1).
The river's morphology in this area is determined by the fluvial dynamics which
sends a large volume of eroded material from the Himalayas to the flood plains.
The deposits are generally made of fine sand, silt and clay. The braided pattern
which starts right from Haridwar, is formed by alluvial deposits. Though braiding is
the main feature in this zone, meanders also develop extensively along the course.
Owing to braiding and meandering, the river's course oscillates from northwest
to southeast and return with the alternate growth of alluvial fans in the river-bed.
This oscillating course gives rise terraces, marshes, point-bar deposits too. The
National Atlas Organisation reported in 1975 that from comparative study of aerial