River flooding response to ENSO-related monsoon precipitation: Evidence from late Holocene core sediments in the Jianghan Plain

In the Jianghan Plain, known as the province of thousands of lakes, monsoon precipitation-induced floods carrying large amounts of sediments can shape the depositional landscape, particularly after frequent river flooding. Therefore, the sediments document abundant information on climate change and its interaction with the fluviolacustrine system and paleoflooding. To date, late Holocene paleoflood records are limited, as continuous paleoflood archives are scarce. Here, using grain size end-members and sensitive components in combination with element records from the JH001 sediment core in the Jianghan Plain, nine continuous paleoflood regimes were identified during 3400–3000, 2750–2550, 2050–1820, 1800–1650, 1550–1500, 1350–1100, 1050–1000, 800–750, and 620–600 cal yr BP, respectively. Exploration of the climatic driving factors on flood regimes indicated a good agreement among paleoflood regimes and El Niño-Southern Oscillation (ENSO)-related hydrological records in the Middle Yangtze Valley (MYV) and reconstructed ENSO records. This suggests that ENSO is the dominant influence on flood occurrence in the Jianghan Plain. Strong ENSO activity exerted a southward shift in the subtropical high in the western Pacific and produced a long-lasting rainbelt in the mid-lower Yangtze Valley, which induced the occurrence of floods in the Jianghan Plain. The evolution pattern of sedimentary environment demonstrated that the floods led to river overflow and overbank expansion, even causing the rivers to divert and bifurcate. The overflow channels carried and deposited silt sediments in the floodplain, which shaped the specific alluvial-lacustrine landscape of the Jianghan Plain. Our results indicate that the grain size of core sediments is sensitive to the occurrence of paleofloods, and that ENSO-related paleofloods significantly influenced the fluviolacustrine sedimentary evolution. These findings are highly useful for regional flood planning and environmental protection in the eastern Jianghan Plain in the context of global warming.