Mapping the wetlands of Mumbai and surrounding area using Remotely sensed Sentinel-2b data

Abstract

Mumbai is richly surrounded by unique types of wetlands such as mudflats, mangroves, saltpans, creeks, freshwater lakes, and estuaries.As the city is highly developed, population explosion and the urbanization are the greatest threat for the wetland ecosystem. Wetland mapping and classification were carried out using the sentinel 2b data for Mumbai and the adjoining areas.Sentinel 2b data from 28th May 2019 was used in this study.The data was processed in the SNAP (Sentinel Application Platform) toolbox.Classification of wetlands has carried out in both pixel-based and index-based techniques.Six different classes were defined in the pixel-based classification they are Backwater, Mangroves, creek water & inland waters, urban area, Forest, and sea.Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Modified Soil-adjusted Vegetation Index (MSAVI2) were calculated in the index-based classification. As per the pixel-based classification results, the percentage of the backwater is 8.54 in the study area, which is 137.077 km². 67.089 square kilometers are classified as Mangroves.Creeks and Inland water are occupying 6.89% of the total study area with the 110.58 km².Saltpans and the Mudflats are the other wetlands found in the study area.Saltpans in Mumbai are around 20km^2, and it is difficult to classify. Mudflatsare mainly found, and around the Thane creek,and the total area of the Mudflat in the Thane creek is classified as 51 km².For the reliability of the result and validating the remote sensing classification, the error matrix technique was carried out.The overall accuracy of the supervised classification result of the study area is found as 0.92. With the overall accuracy of 0.92, the study proved that the sentinel data is more capable of mapping wetlands though it shows less accuracy for classifying the water bodies.The study shows thatSaltpans and Mudflats are massively in unsafe conditions. This study confirmed that the Mangrove area is found to be more stable,maybe because of strict orders of the High Court when compared to the past, though they are under threat by urbanization.