Spatio-temporal Change of Drainage Network at Human-Nature Interface and Its Future Implication to the Estuarine Environment in Gosaba Island, Sundarban, India

Abstract

Gosaba C.D. Block is an active tidal island of the Indian Sundarban. In this island, human-induced modification of the natural drainage system poses serious threats to the estuarine environment. It was started during the British colonial period through the construction of embankment to protect the reclaimed coastal land from saline water ingression. The rapid growth of population over the last few decades has triggered the changes in the drainage network and also altered the land use land cover of the study area. The human encroachment on the drainage area has hampered the sedimentation process as well as water circulation in the delta. As a result, the island is gradually transforming into saucer-shaped form, which aggravates various coastal threats like flood inundation, waterlogging and embankment breaching during extreme environmental events. To study the spatio-temporal change of the drainage network pattern from 1955 to 2018, different multi-temporal satellite images, US Army Toposheet, Census of India Report (2001 and 2011) and Human Development Report (2014) have been used as a source of secondary data for the analysis in ArcGIS environment. In addition to this, instrumental surveying has been done to measure the slope direction in relation to land use land cover and a questionnaire survey was conducted to understand the livelihood status of people influenced by various coastal threats and risks due to the drainage congestion. The study reveals that population density has gradually increased in recent decades and is negatively correlated with the drainage density on the island. The choking of the surface drainage canals has increased the problem of waterlogging in agricultural fields, which affected their productivity. Therefore, a strategy for management of the drainage network needs to be urgently implemented in order to protect the life and livelihood of rural people from various coastal threats.