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An Encyclopaedia of Indian Archaeology v1.c14.s10: 9.10 River Valleys and Changes in River Courses

An Encyclopaedia of Indian Archaeology v1.c14.s10

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9.10 River Valleys and Changes in River Courses

9.10.1 Pleistocene

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River valleys are the most common and important land-forms in every country. They come into existence as soon as the water on the land begins to flow over the uneven natural surface. Further developments in river valleys take place by the erosion of the bed-rock and the deposition of the sediments thus formed. As each stream carves its own valley several streams in the drainage network form several valleys which coalesce with each other and the resulting landscape presents a topography of hills and valleys. Normally each river valley passes through three stages—young, mature and old—from the source of the river to its end in the sea, lake-basin or some other river. The valleys are deep, gorge-like in the mountainous tract, V-shaped at the lower altitudes, broad and shallow on the plains and deltaic near the sea coasts. Depending on climate, underlying geological foundation and differential erosion of rocks, the stage in the cycle of river life, etc., they develop straight, braided or meandering courses.

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In India some rivers have perennial water like the Himalayan rivers which are fed by the melting water of glaciers as well as water received during the monsoon. The Narmada, Tapti, Godavari, Krishna, etc., of peninsular India swell during the rainy season but the quantity of water dwindles during other seasons. The majority of small rivers however carry water only during the monsoon but dry out later very rapidly.

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Rivers have provided a suitable environment for human settlement at all times—from the prehistoric period down to the present day. In the prehistoric times man being a hunter and food-gatherer obtained most of the requirements for his sustenance in the river valleys which bore thick natural vegetation and wild animal life. Later on, when animals were domesticated and the cultivation of crops was initiated, man continued to occupy this land-form as it provided natural fertile soils on the river flood plains for raising crops. Thus numerous Stone Age sites have been discovered in the valleys of the Ganga, NARMADA, TAPTI, GODAVARI, Sabarmati, etc., and their numerous tributaries. Rivers have yet another advantage in that they provide an easy communication for movement for trade, invasion, etc., and it can be seen that important trade routes of ancient times are located in the river valleys.

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Every river is prone to change its course, and this is brought about by differential erosion of the bed-rock, climatic changes and eustatic and tectonic effects. Waterfalls, meanders, ox-bow lakes, river terraces, etc., are some of the most conspicuous land-forms thus created. The more powerful down-cutting streams in the mountainous tract often capture (river piracy) water of the less powerful adjacent streams and the valley of beheaded streams is often dry.

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The TAPTI, NARMADA and Ganga-Yamuna are examples of tectonic valleys (rift valleys) which were the areas of excessive sedimentation during the Quaternary and have preserved a more or less continuous stratigraphic record of the prehistoric past in the form of Stone Age artefacts and fossils of contemporary animals.

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The Quaternary climatic changes [7.3] have been recorded in the Indian river valleys in the form of massive alluvial cones (the BANGANGA-BEAS valleys), morainic deposits (the LIDDAR near Pahlgam, Kashmir basin), lake deposits (*karewas* in Kashmir) and cut-and-fill valleys [9.9] in the peninsular area, and with all of these river valleys are associated human settlements of different periods.

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For river valleys see respective entries in vol. II.—R.V. JOSHI

9.10.2 Holocene

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The importance of rivers as the main source of water, soil and means of communication, which have been the essential items for the growth and development of early cultures cannot be overemphasized. It has been amply demonstrated by the distributional pattern of the early sites [14.1.2]: they are concentrated in river valleys.

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For the Palaeolithic [4.2-4] hunter and gatherer rivers were the major source of his particular needs—the game and the wild fruit as well as the raw material for making tools [9.10.1]. For the Mesolithic [4.5] hunter and gatherer the importance of rivers somewhat decreased since the microlithic tools could be made on any small piece of fine-grained stone and small game could be found in all kinds of environments. But its importance became decisive once the Neolithic [4.6] farmer ushered in the era of sedentary life; without a perennial source of water neither agriculture nor stock-breeding was possible. From now onwards, until long-distance canals were introduced, river valleys in a congenial climate and landscape alone remained the areas of attraction for the people. But this very fact had also an adverse effect on the life of the people in areas where rivers changed their courses—the settlements had to be shifted to some other river valley or to the new channel that a particular river had made.

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Rivers do not change their courses unless some strong geophysical changes or disturbances or climatic oscillations take place. Since such phenomena did not take place in the stable mass of peninsular India in the post-Pleistocene [9.8.4] period, one rarely comes across a total abandonment of a major river valley at any stage of the sedentary cultures. If a site was abandoned it was mainly due to socio-economic [or political] reasons. But the situation in the n. plains was much different. Explorations and excavations conducted in the Indo-Ganga divide by Ghosh, 1952; Raikes, 1968, and others clearly show that rivers like the Ghaggar (SARASVATĪ) Chautang (DṚṢADVATĪ) and YAMUNĀ changed their courses several times, directly affecting the settlements. The field investigations made by drilling the land at three places in the Ghaggar bed near KALIBANGAN and the geomorphological observations made in the field by studying detailed maps Raikes came to the conclusion that about 6000-5000 B.C. there were only two river systems—the Indus and the Ganga. The Yamuna as a tributary of the Ganga was where it is today. Then about 2500 B.C. the Yamuna shifted its course w. wards and joined the Ghaggar. Incidentally at that time the SUTLEJ also discharged its water into the Ghaggar. This mighty river then flowed through the Bahawalpur region and joined the Indus lower down the present-day junction of the Chenab and Indus. In its valley Harappa [4.9] and pre-Harappa [4.18] (SOTHI) sites have been located by Stein, 1942, and Ghosh, 1952. But these sites seem to have been abandoned around 1700 B.C. Raikes feels that this took place because at that time the Yamuna shifted back to its original channel. Singh [7.4, with references], on the basis of his findings on the pollens collected in the Rajasthan lakes, has come to the conclusion that at that time rainfall decreased considerably and desiccation of land set in. For about 600 years hardly any population seems to have lived permanently in the Ghaggar valley. But then suddenly due to coriolis force (deflection force due to the earth's rotation) the Yamuna witnessed its right bank ovulsion somewhere near Indri. About 1100 B.C. once again the Yamuna started flowing w.wards and supporting the Ghaggar, albeit with less water. The Ghaggar system had now narrower water-channels than those it had in the Harappa times. A new set of people, the users of the PGW [4.15], now occupied it. Their sites are therefore found located within the older bed of the Ghaggar but along the new banks of the channels. In the Ghaggar valley no Harappa mound was ever reoccupied by the PGW people. Up to about 500 B.C. the situation remained the same when the Yamuna once again came back to its present channel. Consequently the PGW people also seem to have moved out of the Ghaggar valley. History repeated itself in *c.* 100 B.C. and the Yamuna was once again captured by the Ghaggar. We have a number of early historical sites of the RANG MAHAL culture [4.18.2] along the rejuvenated channel in the Ghaggar. These again were abandoned around A.D. 500, possibly due to the Yamuna going once again to its old e. channel.

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This series of alternating captures of the Yamuna by the Ghaggar and the Ganga systems has been supported also by the presence of numerous small lakes shaped like ox-bow, typical of abandoned rivers, in the Ghaggar-Yamuna divide. There is now in Haryana what is called the W. Yamuna Main Canal which follows the dried-up channels formed anciently by the changing courses of the Yamuna. A large number of sites of the SOTHI culture have been located along these old abandoned channels [see SARASVATĪ VALLEY]. In the same valleys a number of PGW sites have also been found.

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Much of the above is conjectural (and largely based on the find of the so-called Yamuna sand in the borings of the dry bed of the Ghaggar; there is strong literary evidence that during the Vedic times both the Sarasvatī and Yamuna flowed independently, *Ṛgveda-saṁhitā*, 10.76.7), but the corresponding archaeological facts are solid. Another example of the Yamuna changing its course also comes from the Bharatpur region where we have not only a concentration of PGW sites but the ox-bow lakes and a modern canal—the Gobardhan drain system (Gupta *et al.*, 1976).

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[The Ganga has shifted about 8 km e.wards near HASTINĀPURA, now leaving the ancient site, which is known to have been situated on its bank, near its old bed represented by a streamlet (Lal, 1954-5). Much further down PĀṬALIPUTRA was originally strategically situated on the confluence of the Ganga and Son after the latter flowed for some distance parallel to the s. of the former but now the junction is several km upwards. Instances of such changes in river courses can be multiplied. They have often left ancient sites once situated on river banks high and dry and have destroyed them partly or even altogether.]

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Ghosh, A., 1952, in *Bull. National Inst. of Sciences in India*, 1, New Delhi (for sites on the dried-up valleys of the Śarasvatī and Dṛṣadvatī). Gupta, S.P., *et al.*, 1976, in *Palaeoclimate & Arch. of Rajasthan and Gujarat*, 1976 (for PGW sites in relation to the river beds in Rajasthan). Lal, 1954 and 55, in *AI*, 10 and 11, p. 9 (for location of Hastināpura). Raikes, R., 1968, in *Antiquity*, 42, pp. 286-91 (for Kalibangan and courses of the Ghaggar-Yamuna). Rydh, Hanna, 1959, *Rang Mahal*, Lund (for the Ghaggar) Stein, A., 1942, in *Geographical Jour.*, 99, pp. 173-82 (for sites on the Śarāvastī. For sites and river valleys see respective entries in vol. II.—S.P. GUPTA

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