An Assessment of Physiographic Habitats, Geomorphology and Evolution of Chilika Lagoon (Odisha, India) Using Geospatial Technology

Abstract

The coastal lagoon ‘Chilika’ along the Bay of Bengal shore (Odisha state, India) support a productive wetland ecosystem that influences the livelihood of local people by providing large scale fishing activity within the lagoon water body, pasturing in the lagoon fringe marshes by rearing livestock and promoting ecotourism in the islands and spits of the lagoon system using nature as magnet of attractions. The lagoon is shore parallel elongated water body enclosed with barrier spits and narrow tidal entrances, and extended in between Mahanadi deltaic distributary channels to the north east and Rishikulya River to the southwest. The average water spread area of Chilika is 1,165 km2 during rainy season and gradually it shrinkages to 906 km2 during summer months with average depth ranges from 1.70 to 3.70 m. Physiographically, the lagoon habitats are categorized as (i) Daya-Bhargavi deltaic flats with extensive fresh water wetlands, (ii) brackish water marshes and tidal flats, (iii) islands with marshes and transition vegetation, (iv) islands with mangrove swamps, (v) fresh water weeds of lagoon fringes, (vi) sand spits and dunes, (vii) and lagoon water bodies. All these habitats are showing significant variations related to geological, sedimentological, hydrological, climatic and ecological factors. Northeastern parts of the lagoon water body have been swallowed by deltaic sedimentation; barrier back shores, islands and other lagoon fringes have shrunk as the result of bordering accretion and encroachment of marshes, weeds and swamps; however, southwestern parts of the lagoon are narrowed, and in some places near-segmented by growth of spits and coalescence of headlands and islands. Opening of tidal inlets have been shifted from one place to other place with time across the enclosed barriers to achieve the balance between water levels of the lagoon and open marine shelf, and as a result of interaction of fresh water from rivers with salt water from the sea during floods and cyclones in the region. Historically, the habitats of Chilika lagoon provided favorable conditions for maritime trade and commerce, as well as modern fishing related livelihood support system to the local people; but dynamic landscape changes of the lagoon with sedimentation have produced significant effects on human systems by changing salinity regime and eutrophication of enclosed water body. The paper highlights the gradual changes of coastal lagoon systems with variety of habitats influenced by sedimentation, fresh water inputs, local sea levels, tidal mixing and dynamic wetland geomorphology. Chilika habitats, their geomorphologic changes, ecologic responses, and evolution of the lagoon itself are studied in the present paper using geospatial technology with temporal image data, as well as with available archaeological remains of past maritime activities and existing dating records for better management option and conservation of degraded habitats.