The Aral Sea basin in Central Asia and its major rivers, the Amu Darya and Syr Darya, were the center of advanced river civilizations, and a principal hub of the Silk Roads over a period of more than 2,000 y. The region’s decline has been traditionally attributed to the devastating Mongol invasion of the early-13th century CE. However, the role of changing hydroclimatic conditions on the development of these culturally influential potamic societies has not been the subject of modern geoarchaeological investigations. In this paper we report the findings of an interdisciplinary investigation of archaeological sites and associated irrigation canals of the Otrār oasis, a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage site located at the confluence of the Syr Darya and Arys rivers in southern Kazakhstan. This includes radiometric dating of irrigation canal abandonment and an investigation of Arys river channel dynamics. Major phases of fluvial aggradation, between the seventh and early ninth century CE and between 1350 and 1550 CE coincide with economic flourishing of the oasis, facilitated by wet climatic conditions and higher river flows that favored floodwater farming. Periods of abandonment of the irrigation network and cultural decline primarily correlate with fluvial entrenchment during periods of drought, instead of being related to destructive invasions. Therefore, it seems the great rivers of Central Asia were not just static “stage sets” for some of the turning points of world history, but in many instances, inadvertently or directly shaped the final outcomes and legacies of imperial ambitions in the region.

A joint Kazakh-British archaeological initiative undertook a survey and excavation of the city of Kuik-Mardan, one of the largest of the seventy or so known settlements in the Otrar oasis on the Syr-Darya river, Kazakhstan. Several complimentary field techniques were employed including unmanned aerial vehicle photomapping and an extensive programme of radiometric dating. The radiocarbon dates obtained are the first for any city in the oasis and allow more confident interpretations of the experience of the city to be ventured. Also undertaken was a geoarchaeological investigation of the surrounding irrigation and water supply canal system. Key results include its wholesale destruction during the 6th to 7th century and the form of the later occupation of the city.

Five early-19th-century Thames lighters, up to 22 m long, in an excellent state of preservation, were recorded during preconstruction archaeological works. The lighters had been used as the main structural elements in a mid-19th-century riverwall. The lighters and river-wall are described, and aspects of the construction discussed. The craft exemplify utilitarian trends in early industrial age boatbuilding, and were essential in the development of the international port. Although comparatively recent in date, details of their 'bottom-up' construction are not well known.

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