An alternative approach to delineate wetland influence zone of a tropical intertidal mudflat using geo-information technology

Abstract

Mudflats are important tropical coastal wetlands having high carbon sequestration and biodiversity potentials. The actual reach of a mudflat environment spreads far beyond its perennial wetland areas in a coastal site. Accurate demarcation of the extent of these buffer areas is imperative for sustainable wetland management. This study tried to delineate the wetland influence zone (WIZ) of an intertidal mudflat in the Medinipur coastal plain, India as a functional extension around the considerably smaller yet hydrous cum muddy depressions. Normalized Difference Water Index (NDWI), derived from Sentinel-2 MultiSpectral Instrument (MSI) datasets, and Temperature Vegetation Dryness Index (TVDI), derived from the coupled use of Sentinel-2 MSI and Landsat-8 datasets, had been analyzed and merged to develop nine characteristic zones. Among these, eight zones (Zone I to Zone VIII) were identified as part of the WIZ and the rest one (NDWI: < −0.15, TVDI > 0.7) was considered as a supra-tidal zone, devoid of the mudflat features. Although the overall extent of WIZ (Minimum: 339.20 ha, Maximum: 350.22 ha) did not change much from 2016 to 2020, the inter-zonal spatial arrangements of vegetation and physiography transformed continuously. The gradual disappearance of the major tidal creek from the south-western parts and increasing human footprints throughout the mudflat had expedited this transformation. Accordingly, periodic assessments incorporating microwave and optical datasets along with high precision in-situ measurements of soil moisture was suggested for the efficient monitoring of these fragile tropical ecosystems.