Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Vishwas S. Kale ¹, Sheila Mishra ², Victor R. Baker ³

Affiliations
1 Department of Geography, University of Pune, Pune 411 007, IN
2 Department of Archaeology, Deccan College, Pune 411 006, IN
3 Department of Hydrology and Water Resources, University of Arizona, Tucson AZ 85721, US

Abstract

A continuous record of the largest Narmada floods over the last 2000 years was obtained from Sakarghat, on the Narmada River from a study of slackwater flood deposits. Two sequences of extreme floods date between ca. 400 and 1000 AD and post-1900 AD. The period, 400-1000 AD representing a period of less frequent but more extreme floods, has been documented in the archaeological record as one of decline of human settlements.

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Victor R. Baker ¹

Affiliations
1 Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721-001 1, US

Abstract

A great weakness of various intenational scientific initiatives global change, earth system science and related hydrological assessment of flood hazards is their overemphasis on prediction from idealized conceptual models. The latter are abstract constructs made possible by rapidly increasing computer power but predicated upon often unverified and sometimes unverifiable assumptions. It is now realized that abrupt climate change and extreme events pose more of a global change hazard than do the mean climate phenomena predicted by global climate models (GCMs). For 20 years there has been an overemphasis on developing these models as the principal tool for dealing with threats to habitability of the planet. In contrast to unverified predictions of the future given by GCMs, palaeoflood data provide evidence of Real-Work cataclysms that people can understand sufficiently to alter their perceptions of hazards, thereby stimulating appropriate action toward mitigation. This issue is particularly important in the world's tropical monsoon areas, which are prone to especially extreme floods and high variability in their magnitude and frequency. These areas, which are inhabited by half of the Earth's human population, also have excellent sources of palaeoflood information, which comprise a natural archive that can appropriately stimulate productive hazard reduction.

Keywords

Flood Hazards, Climate Models, Science Policy, Palaeofloods, Global Change.

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Vishwas S. kale ¹, Victor R. Baker ²

Affiliations
1 Department of Geography, University of Pune, Pune 411 007, IN
2 Department of Geosciences, University of Arizona, Tucson, AZ 85721, US

Abstract

Fluvial archives include slackwater flood deposits (SWD), which not only preserve informatron about centennia to millennial-scale changes in the flood regime conditions, but also provide information on climate vanability and extreme climatic events The present study is based on SWD evidence from six large rivers in central and western Indla A remarkable feature that has emerged From the palaeoflood analyses is that the evidence of large floods between circa 14^thand 19^th century AD is generally missing. Considering the manner in which the rivers build the palaeoflood sequences in stable bedrock gorges, the striking and conspicuous absence of flood deposits of this period indicates a significantly reduced frequency of large floods Since modern floods on these rivers are the result of severe cyclonic storms, the absence of large palaeofloods not only implies a sharp decline in the frequency of flood-producing severe cyclonic systems, but also an overall decrease In the summer monsoon intensity Interestingly, this period of less frequent large floods (ca 14^th-19^th century AD) approximately coincides with the Little Ice Age (1300 to 1850 AD), which was characterized by relatively cool and dry conditions, and a weakening of the Indian summer monsoon.

Keywords

Palaeofloods, Slackwater deposits, Extreme climatic events, Monsoon intensity, Little Ice Age.

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