A sub-centennial-scale OSL chronostratigraphy and Late-Holocene flood history from a temperate river confluence

River confluences can be meta-stable and contain valuable geological records of catchment response to decadal-millennial scale environmental change. However, in alluvial reaches flood stratigraphies are particularly hard to date using 14C. In this paper we use a novel combination of optically stimulated luminescence (OSL) and multi proxy sedimentological analyses to provide a flood record for the Severn-Teme confluence over the last two millennia which we compare with independent European climate records. The results show that by c.2000 BP the Severn-Teme confluence had stabilized and overbank alluviation had commenced. Initially this occurred from moderately high flood magnitudes between c.2000-1800 BP (50 BCE-CE 150), but was followed from 1800-1600 BP (CE 150-350) by fine alluvial deposition and decreased flood intensity. From 1600-1400 BP (CE 350-550) the accumulation rate increased with evidence of large flood events associated with the climatic deterioration of the Dark Age Cold Period. Following a period of reduced flood activity after c.1400 BP (c. CE 550) larger flood events and increase in accumulation rate once again became more prevalent from c.850 BP (c. CE 1100) coincident with the start of the Medieval Climate Anomaly, a period associated with warmer, wetter conditions and increased land-use intensity. This state persisted until c.450 BP (c. CE 1500) after which increased flood magnitudes can be associated with climatic variations during the Little Ice Age. We demonstrate that from the combination of high-resolution dating techniques and multiple analytical parameters, distinctive phases of relative flood magnitude vs flood duration can be determined to a detailed chronological precision beyond that possible from 14C dating. This permits the identification of the regional factors behind floodplain sedimentation, which we correlate with the intensification of land-use and climatic drivers over the last two millennia