Decomposing Holocene flood variability in the Pannonian Basin using singular spectrum analysis of a grain-size sedimentary proxy

The Holocene hydro-climatology of the Pannonian Basin remains poorly constrained due to the inherent noise and temporal resolution of many fluvial sedimentary records. This study presents a high-resolution reconstruction of flood frequency and magnitude from the Tövises site in the eastern Great Hungarian Plain, utilizing Singular Spectrum Analysis (SSA) on a grain-size-based flood proxy (EM4). Integrating SSA, End-member modeling (EMM) and compositional data analysis (CoDA) effectively isolates the in situ oxbow sedimentation from high-energy climate-driven flood deposition. Analysis reveals that the low-frequency SSA component (RC3) reflects long-term geomorphic evolution of the oxbow–floodplain system, while the higher-order oscillatory components (RC2–RC5) capture the millennial-to-centennial climatic scale variability. The SSA revealed a progressive decline in flood frequency alongside three climatic oscillations: a dominant Hallstatt-scale cycle (∼2100 yr), representing the primary external forcing, and two subordinate oscillatory modes: a Bond-scale cycle (∼1400–1500 yr), and a centennial-scale cycle (∼850 yr). This multi-centennial variability is consistent with Holocene-scale fluctuations in North Atlantic climate fluctuations, including periods of enhanced ice-rafted debris (IRD) deposition. Despite chronological uncertainties limiting precise event-by-event synchronization, major flood phases identified between circa 5.5–3.0 ka BP and post-1.5 ka BP correspond to high-energy overbank sedimentation in the EMM and CoDA models. This integrated framework reinforces the influence of solar and oceanic forcing on regional paleohydrology and provides a critical baseline for evaluating flood risk in low-gradient areas of Central Europe under modern climatic scenarios.