Luminescence chronology of late-Holocene palaeofloods in the upper Kaveri basin,India: An insight into the climate–flood relationship

Abstract

Instrumental/historic records have helped to understand the extreme flood–climate relationship in the modern environment; however, few studies are available to understand their long-term relation (10²–10³ years) due to the poor preservation and lack of dating techniques. It remains uncertain whether extreme flooding is linked with long-term wet phases of climate or a random event caused by an unusual downpour irrespective of climate. Luminescence analysis of quartz grains from river/floodplain sediments in the Kaveri basin, southern India, showed heterogeneous bleaching. We demonstrated the successful application of various statistical age models in estimating ages of heterogeneously bleached young sediments. This study shows distinct flood clusters occurred during the times of major shifts in the monsoon climate, from fluvial dormancy to sudden outburst of monsoons (~2 ka), from warmer to colder (onset of ‘Little Ice Age’ (LIA) ~ 14th century), from colder to warmer (end of LIA ~ 19th century) and ~20th century, indicating that climatic pattern can be associated with more frequent occurrences of extreme flood events. The study also shows that the two major flood events of the 20th century reported from the upper Kaveri were produced by high intensity short duration storms, suggesting that not all wet phases are associated with major floods and all dry phases with low floods/droughts. The excellent match of the chronology with the historical data, instrumental data and published literature based on proxy data on the Indian summer monsoon validates the chronology and the potential of sedimentary archives for future palaeoenvironmental reconstruction of the study area.