History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c32.s2.t6: Embankments
History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c32.s2.t6
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Embankments
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Embankments form an essential part in the construction of river banks, canals, and reservoirs. They are artificial wide wall of stone or earthern mounds which are built to keep the rivers, canals and tanks from overflowing the banks. They are essentially constructed to impound water and also to increase the storage capacity of reservoirs. The artificial embankments were used in the Vedic period.
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They are mentioned in association with dams or barriers in the *Ṛgveda* as *Kṛtrimāṇi rodhāsi* (*RV*. II. 15.8). The embankments surrounding the rivers with whirls were known as *rodha cakraḥ* (*RV*. I. 190.7). They were, no doubt, earthern without regular masonry. So the idea of erecting embankments was current in those days and actually practised.
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Kulai and *ārrukkulai* are the terms in Tamil used to denote the tank bund and river embankments respectively (ANRIE No. 292, 1908; *SII*.V.p. 603). The inscriptional evidence in Tamil clearly shows that the embankments of tanks were allowed to be raised within their limits to hold the maximum quantity of water. The Tiruvālaṅgadu plates of the Cola Rajendra I, for instance, the following specification: “the embankments of the tanks of this village shall be permitted to be raised within their (own) limits (to any suitable height) so as to hold the utmost quantity of water that may be let into those tanks” (*SII*. III, NO. 205. 11. 426 ff.; also ANRIE, No. 103, 1921).
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We get a few references from the inscriptional sources about the material involved in the construction of embankments. While recording the restoration of the famous Sudarśana lake by Rudradaman I, the Junagadh inscription says that its embankments are stony, in breadth, length and height constructed without gaps as they are of stone (clay)" (*EI*. VIII. No. 6, p. 46). We do not know when the great embankment, over 100 feet thick at the base, finally crumbled. During the days of the Cola Karikāla the Kaveri was impetuous and of considerable magnitude. The Ceylon Chronicle *Mahāvaṃśa* says that he invaded the island of Ceylon (Sri Lanka), carried away about 12,000 captives and set them up to work on the construction of the banks which extended along the course of the river to a distance of about 100 miles from its mouth (Kanakasabai Pillai, 1904, pp. 8-9). This is well reflected in an eleventh century epigraph. “He (Karikāla), who curbed the pride of the subordinate, prevented the Kaveri, which by its extensive floods caused the earth to be deprived of its produce, by means of a bund formed of earth thrown in baskets carried in hand by (enemy) Kings" (TRV. III, pp. 154-155). This age-old and time-tested method of strengthening the river banks is still being adopted in rural area in South India. The excavation conducted by the Archaeological Survey of India since 1915 have clearly established that canal embankments were constructed with hard lime gravel mixed with stones which were rammed to withstand the rush of water. Bricks of unusually large size 24" ×12"×3" and of extremely durable nature were used in the construction of walls. Evidences show that in the later centuries the river banks or tank embankments were either raised out of earth or reinforced with stone revetment. In some cases granite stone blocks were used for the basement of embankments (Karthikeya Sharma, 1958-59, pp. 307 ff; Raman, 1968, p. 239).
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The unabated technical skill of the tank builders in ancient India will be fully realised if one could make an in situ study of some of the tanks which still exists even to this day to afford irrigation facilities. A.F.Cox in North Arcot District Manual describes the Mahendra Taṭāka excavated by the Pallava Mahendravarman I in Mahendravāḍi (North Arcot District) thus: "The bunk (manmade embankment), is enormously high and might be restored to its original height, in which case a great extent of land could be brought under irrigation" (Cox, II. pp. 438 ff.). The tank at Kaveripakkam constructed by the Pallava Nandivarman III (c. 844-856 A.D.) is the largest tank in the same above mentioned district. Its extensiveness is exhibited by a "bund about four miles stretching from North to South" (Cox, II. pp. 438 ff). The bunk of the Viranam tank created by the Cola Parāntaka I is ten miles in length, and has mean width of above 3 miles. The large irrigation reservoir "Colagaṅgam" created by the Cola Rajendra I near the capital in the Tiruchirapalli district has an embankment of sixteen miles long running from north to south and provided with several sluices and channels for the irrigation of a large area (Nilakantha Sastri, 1955, p. 234).
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Trees on the Banks of Tanks: The practice of planting trees on the taṅk bunds was in vogue in ancient times. The Sudarśana lake which was destroyed by a storm during the reign of Rudradaman in A.D. 150 was restored to its original glory by strengthening the dam and planting trees on all banks. In some places particularly in Āndhradeśa rows of trees called Kaṭṭava were planted on or by the side of the tank bund, evidently with a view to adding to its strength (CTI. No. 53; also Yazdani, 1964, p. 679). In Tamil country five fruit bearing trees, the Indian gall-nut, Nelli (Phyllanthus embalica or the embalika myrobalam), Tantri, Karañja-puṅga (Indian beach Pungania glabra) and Aśvatha (the Fig tree or Ficus religiosa) were generally planted all along the bunds of tanks. The principle which underlies the planting of such trees on the bunds of tanks is easily intelligible.
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Trees arrest the soil erosion due to sudden or frequent floods and also hold up the water level which would fall without the banks. Hence the presence of trees near the tank was found very useful. Moreover, they contain some tannin in them. The tannin adds a slight sweet taste to the water and thus masks any excess of chlorine in drinking water. "It is also useful in cleaning the water of its impurities on the surface by carrying down to the bottom all dirt and clay that the water may contain, thus serving the same purpose as alum”. Hence these trees are generally planted near the bunds of drinking water tanks" (Venkatarama Iyer, 1916, p. 184).