Abstract This study diagnoses temporal and spatial variations in the performance of different social-ecological systems (SES) in coastal floodplain management in the Ganges-Brahmaputra delta. We go beyond common pool resource management problems and address the management of local public goods. In the assessment, we consider recent developments in the framework initially developed by Elinor Ostrom. The main variables of the framework that we use are resource systems, the environment, the governance system and actors. The focal SES is defined based on guiding questions relating to the definition of the key problem, system boundaries, and action situations. According to our results, the performance of resource systems and the environment deteriorated in 1960–79 compared to the performance prior to 1960. The condition reached a low point during 1980–1999 but improved slightly after 1999. The horizontal network structure of local governance was active until 1960. Due to the introduction of the ‘tidal river management’ approach in the 90 s, the performance of the resource system and the environment has slightly improved, as has the involvement of government and non-government organizations. Our results also show that overall SES performance is comparatively better <in the case of locally managed floodplains than it is for those managed by government agencies. Our new approaches, such as the recent development of the diagnostic framework, the guiding questions for defining focal SES, and application of the framework to local public goods can potentially be used in the fields of sustainability science and SES science. The qualitative performance of each of the selected indicators is useful for identifying intervention options to achieve a sustainable outcome for the coastal floodplain SES.