What is the influence of Geomorphology on Waterways?

While roads and railways can to a considerable or great extent overcome the obstructions posed by geomorphology, waterways can do so to a very limited extent. These way waterways are practically ruled out from mountains or difficult hilly terrain.

In 1957 Vasudeo gave a master plan for inland navigation. The outlines of his scheme are as follows:

(i) A coastal canal will connect Calcutta and Sunderbans with Mangalore across the Mahanadi, Godavari and Krishna canals and Kerala kayals (lagoons).

(ii) A navigation system will extend from Haridwar to Calcutta mainly along the Ganga and its canals. The other major tributaries of the Ganga, viz. the Ghaghara, the Rapti and Gandak and the Chambal, the Betwa and the Son along with canals of the Son will be made navigable.

(iii) The Chambal and the Betwa will be joined with the Narmada, the Godavari with Tapti and the Narmada through the Wainganga and the Mahanadi with the Son.

Thus, this scheme suggests three inland navigation systems: (a) a north-Indian particularly the Ganga system; (b) a coastal system and (c) a central peninsular system.

Originally, such an inland navigation scheme came from Sir Arthur Cotton in the form of lectures on ‘Irrigation Works in India’ at the School of Military Engineering at Chatham in England.

The Central Water and Power Commission of the Government of India developed a Master Plan for inland navigation on the basis of Cotton’s views. Vasudeo in his article mentioned above has outlined the Master Plan. India has a total of c. 9,268 km of navigable waterways. Of this, about 4,827 km are navigable rivers. The rest are canals and coastal backwaters.

Now examining the existing or proposed waterways, we may classify the relevant geomorphic background into four types: Facilitative; Permissive; Restrictive and Prohibitive.

Facilitative geomorphology is exemplified by the topography of the Indo-Gangetic Plain or coastal lowlands, which because of low gradient and slow flow of water, ensure large volume of water in the waterways making, at least, seasonal navigation possible. For the enlargement and improvement of waterways in these areas, however, some artificial deepening or dredging or other steps for maintaining suitable volume of water will be necessary. This again is related to geomorphology because water is responsive even to subtle geomorphic variations.

Permissive geomorphology for waterways is illustrated by the Central Indian region from the Godavari and the Tapti in the south to the Ganga plain in the north. Here geomorphology imposes obstructions, which can be surveyed and removed with great effort and cost. Apart from the removal of rock barriers, “dams, weirs, locks and probably lateral canals will have to be constructed” to make the waterways suitable for navigation.

Restrictive geomorphology is probably illustrated by mountains of such gradient, relief and height, which make waterway construction and operation mostly impossible. But there may be suitable pockets for restricted and limited navigation in such areas, like Kashmir valley, Kangra valley and Kathmandu basin.

Finally, prohibitive geomorphology is exemplified by such regions as the Great Himalayas, most of the lesser and Outer Himalayas, Western Ghats and other markedly scarped zones like Shillong Plateau, Chotanagpur, Bastar highlands and most of Deccan proper. Lack of low ground or permissive gradient and the dominance of high steep slopes rule out waterways.

The National Water Grid of India (NWGI) proposed by the Central Water and Power Commission mentioned earlier could “transfer billion cubic meters of water in 150 days operation with a lift of 400 meters over the Vindhyas. The Brahmaputra-Ganga link visualizes a transfer of 16 billion cubic meters with a 15-meter lift to divert the Brahmaputra waters into the Farakka pond.” One of the main drawbacks of this scheme is the enormous quantity of power needed for pumping.

An alternative to NWGI has also been presented. It is the Garland Canal Scheme. It was put forward by Dinshaw Dastur, a consultant engineer. F.A.O. is reviewing it. The scheme proposes two giant canals. One will surround the peninsular upland. The other will be along the southern margin of the Himalayas. The two giant canals will be linked by a number of transverse canals. The sub-Himalayan canal, about 3,800 km long, and 400 meters high will connect the Sutlej to Chittagong through the Brahmaputra. The Peninsular canal called, CSC (Central and Southern Canal) will have a length of 8,800 km at a height of 300 meters.

The sub-Himalayan canal will arrest an estimated 860 billion cubic meters (including snowmelt) and transfer the same to CSC pipelines.

“Each of these gigantic trans-basin waterways will be 10 meters deep and have 6 meters high embankments—giving a total height-storing capacity of 16 meters. The canals (3,500 in all) will be constructed perpendicularly to the main canals at approximately 3 km intervals and be 13 meters deep with three meter-high embankments” FAO has sounded a note of cautious optimism.

No doubt, economic, geomorphic and technical feasibility is a precondition. It is expected to cost 1,500 crore rupees. It is thus a colossal affair. The proposed 3,500 subsidiary canals at an interval of 3 km will devour a good deal of land in a land-hungry country. Many villages and towns falling in the alignment of canals will be affected and serious drainage problem may arise. A good deal of cultivated and inhabited area will have to go. Problems of waterlogging and salinity may be other adverse effects. Such, closely spaced network of perennial canals will not only change the face of the land but also its climate, habitat and communication. This giant scheme with gigantic financial needs requires detailed meticulous geomorphic investigations and mapping.