The heritage sewer networks of Kolkata (Calcutta) and ascertaining their coping potential under growing urban pressures

Abstract

ABSTRACT The earliest sewer networks of the city of Kolkata, or erstwhile Calcutta, covered a modest 19.1 km2 of the central district of the city and the first phase of the network-commenced operation in 1868. Calcutta, then, was the capital of imperial India under British rule and the combined sewer was only second in the empire after London. The conduits of this sewered catchment, and of the two others that followed subsequently, continue to be in operation despite heightened base flows due to population rise and increased stormwater runoff because of greater imperviousness arising from urbanisation. The recent lining of the sewer conduits or augmentation of the drainage pumping capacities has not, however, reduced street waterlogging during the monsoons by a great amount. One aim of this study is to investigate the reasons behind this failure of the system and evaluate the sustainability of these historic sewers with the help of mathematical models, verifying them as far as possible with the scant available data. The other objective is to make the reader aware of the engineering heritage of the country and document the available information about the Calcutta sewer networks for providing a base of reference for future researchers.