Rivers convey physical, hydrological, and chemical fluxes across terrestrial landscapes to ocean sinks and interact dynamically with their floodplains (river-floodplain morphodynamics; RFM). Floodplains regulate the impact of short-term hydrological events, trap sediment and nutrients delivered by overbank flow, and fuel riparian ecosystem productivity. Sedimentation and biomass accumulation enable floodplains to react to relative sea level rise. Over longer timescales, RFM govern rates of channel migration and therefore regulate physio-chemical fluxes (e.g., carbon storage, weathering). Consequently, RFM determines the storage capacity of allogenic sediment flux signals and contributes significantly to our understanding of longer-term biogeochemical cycles. Channel-floodplain sedimentary archives (modern and ancient) offer key insight into past channel-floodplain interaction and physio-chemical fluxes. We invite a broad set of contributions that explore and quantify the interaction between channels and floodplains and its relationship to physio-chemical fluxes through terrestrial landscapes into the stratigraphic record.