Deltaic Expansions of the Mahanadi Tri-delta and the Chilika Lagoon: Geospatial Approach

Abstract

Prelude: The major river deltas are sinking, shrinking which accommodate ≈40% of global population. The Mahanadi tri-delta along the east coast of India consists of three river deltas i.e. the Mahanadi, the Bramhani and the Baitarani. The tri-delta encompasses many ecological hubs and the 2nd largest lagoon of Asia, the Chilika Lagoon lies in the southern corner of the delta. Presently the Mahanadi tri-delta and its coastal environments are under threat due to coastal vulnerability, population growth, urbanization and industrialization but the expansion of the delta towards south is observed. Scope: Present research is ubiquitous to know the quantity of sinking, shrinking and subsidence of the Mahanadi tri-delta under congregation of different geological setting, damming, LULC changes, soil erosion, regional sea level rise, and anthropogenic pressure. Also geospatial geomorphic changes in the anastomosis of  the rivers and drainage channels are studied along with expansion of the delta to its southern fringe Methodology: The causes of vulnerability of the delta are estimated from sediment inflow and marine transgression is evaluated. The land use and land cover changes has been evaluated and analyzed by using satellite imageries, remote sensing, GIS tools and ERDAS softwares. Results: The study revealed that due to effect of relative sea-level rise, paucity of sediment influx @ 66.7% to the delta are the main causes for the delta vulnerability accompanied by geo-mining and urbanization. The extention of delta to the south is due to emergence of the Makara river system which carries more flood flow than the existing Daya river. Prominent changes in LU & LC are observed from the satellite imageries of two different period. Changes in the LU &LC of the tri-delta has shown the  extension of the Mahanadi tri-delta towards south and shifting of deltaic boundary from 20 m to 50 m contour line in l landward direction during last four to five decades (recasted).