Observing morphological changes in natural land form through archived satellite images: Case study of the Thane Creek

The Mumbai Metropolitan Region (MMR), located to the east of the Arabian Sea, experiences tropical climate with annual rainfall of over 250 cms. Geographically, the Thane Creek separates the island city from the mainland comprising low-lying marshy lands, and is lined by north-south trending hills on either side. The Creek has historically served as the natural course for rainwater discharge from the adjoining hilly terrain. Owing to its peculiar topography, the city has a distinct linear morphology wherein the habitable area along the Creek lies between the water front and these hills. This has necessitated that creation of new firm land on both its shores would either require cutting of foothills and/ or filling of erstwhile low lying marshy lands, both having fragile ecology of their own. This study highlights the significance of satellite image classification and change detection to observe the effect of rapid development and expansion of urban areas over time in the MMR on the morphology of the Creek and its adjoining wetlands. Change-detection analysis performed on classified time-series Landsat images, using Object Based Image Analysis (OBIA), reveal gradual change in the profile of the Thane Creek over the years. It is observed that the Creek width has reduced on the western shore, due to the siltation caused by anthropogenic intervention, thereby affecting the adjoining wetland ecosystems. The observations provide useful inputs for the stakeholders, to foster a comprehensive action plan to ensure sustainable futures for both mankind and biodiversity.