Monitoring of dynamic wetland changes using NDVI and NDWI based landsat imagery

Abstract

Recent initiatives using the GIS tools for mapping and analysis of wetland dynamics bring the hope for an effective wetland management. Degraded or modified wetlands are more sensitive and less resilient to the climate change. This paper focusses on a study of water bodies in Sirmaur District, Uttarakhand, India with the special focus on Renuka wetland. The Renuka wetland, a Ramsar site is affected by global warming, floods and storms and changes due to precipitation. The updated or accurate maps and spatial and temporal changes of Renuka wetland are not available. Only the details about the flora and fauna have been recorded in this region. Traditional methods in mapping and monitoring, like field survey and sampling, are usually labour intensive, time consuming, and expensive and often fail to detect the changes over the regions of wetland zones. The present study is carried using the online interactive cloud-based planetary processing open source platform, Google Earth Engine (GEE). The wetland maps considered are Landsat 7 and 8 images with cloud cover less than 30% during the summer (May) and winter (September) seasons. The suitability index is also calculated based on the area and perimeter of the water body in study region to demonstrate the characteristic change of Renuka wetland over the selected time period. The missing data of NDVI and NDWI is fitted using the harmonic time series and the resultant map with the supervised classification Random Forest shows a high overall accuracy of 90% with a reasonable Kappa coefficient of 0.8. Using the Global Water Occurrence Explorer, the water changes intensity and the seasonality water change over the wetland for the period of 1984–2019 are studied. The results showed the significant insight into the changes over the study region in terms of pixel range with the presence of water and the change in locations in terms of seasonality and persistence.