The world’s natural floodplains are being lost and degraded by human alterations. The lack of standardized data for quantifying these floodplain alterations, as well as the absence of convergence among data, analysis, and approaches, has led to significant uncertainty. We discover four primary barriers contributing to this problem: (1) discrepancies in defining floodplain alterations, (2) inconsistent floodplain boundaries, (3) insufficient use of data (e.g., over-reliance on population density), and (4) mismatches in the spatial resolution and scale of analyses (e.g., aggregated across basins or countries using temporally fragmented, short-duration data). As the first step to overcome these barriers, we recommend benchmarking global floodplains using high-resolution land-use data and indices of human disturbance and by integrating existing dams and levees within floodplain maps, establishing a global reference floodplain status from which alterations and critical change points can be continuously tracked. We advocate for a new socio-ecohydrological model of floodplain management—one that redefines human alterations by considering both structural changes and functional losses within a balanced framework of benefits and trade-offs.