Land Subsidence in Calcutta under the Effect of Hydrogeological Conditions and Over-Extraction of Groundwater   Amartya Kumar Bhattacharya Senior Lecturer, Department of Applied Mechanics, Bengal Engineering College (Deemed University), Howrah, West Bengal, India Email: amartya_67@rediffmail.com Sudip Basak Lecturer, Department of Applied Mechanics Bengal Engineering College (Deemed University) Howrah, West Bengal, India Email: basackdrs@hotmail.com Monindra Nath Patra BCE, ME PhD Student, Department of Applied Mechanics, Bengal Engineering College (Deemed University), Howrah, West Bengal, India Email: monindra_66@yahoo.com
			ABSTRACT

The work reported herein is aimed towards conducting extensive field investigations to assess the amount of land subsidence in the city of Calcutta under the effects of existing hydrogeological conditions and over-extraction of groundwater. Based on the collected field data, the average pre-monsoon and post-monsoon depths of groundwater at various locations are plotted on the maps. A three dimensional view showing the average piezometric surface for the entire city has also been presented. The places with lowest piezometric levels within Calcutta has been identified as well. With the available informations regarding hydrogeological and soil profile, the amount of land subsidence at nine prime locations within the city of Calcutta is estimated. From the entire investigation, a series of important conclusions are made.

KEYWORDS: Groundwater, Ground Movements, Subsidence.

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