Wetlands and floodplains areas are crucial for biodiversity and ecosystem services, such as regulating hydrological regimes and controlling flood risks. Despite their importance, these environments have been significantly degraded by human activities. Brazil, Australia, and other tropical areas are key regions for global wetland conservation, yet they face severe threats. Australia’s wetlands, covering 4.4% of the country, face degradation, particularly in the Northern Territory. Considering this background, the present study introduces the Wetland Condition Change Index (WCCI) to assess wetland condition changes, focusing on the Adelaide River floodplain in Northern Australia. The WCCI, using Landsat images processed in Google Earth Engine, integrates indicators for soil, water, vegetation, and impervious surfaces. Trends were determined using Sen’s slope, and the results were validated with field observations and accuracy metrics. The Adelaide River Catchment was adopted as a study case, motivated by the lack of updated information. Results indicate that urban and agricultural developments contribute to negative trends, while natural areas show stable or positive trends. The WCCI reveals minimal changes in the Adelaide River floodplain’s wetlands, with some regions impacted by intensive livestock activity and new agricultural developments. However, anomalies in certain areas suggest natural environmental changes needing further investigation. The WCCI proved effective in assessing wetland conditions and can be applied to other tropical regions, including Brazil, enhancing understanding of wetland dynamics and aiding in conservation and management efforts.