Late Quaternary evolution of a lowland anastomosing river system: Geological-topographic inheritance, non-uniformity and implications for biodiversity and management

Lowland multiple-channel rivers are characterised by floodplain-corridor heterogeneity, high ecological and heritage value, can be in quasi-stable states. This holistic study of a surviving temperate zone example (Culm, UK) uses geomorphological mapping, 14C, direct sediment dating (OSL, fallout radionuclides), palaeoecology. reveals the evolution channel-floodplain system from an initial braided state Late Pleistocene to its late Holocene anastomosing state. After Pleistocene-Holocene transition reduced channel incised into braid-plain, only able rework gravels locally due competence relation inherited bounding calibre. resulted creation terrace islands, palaeochannels, stable pattern dominated junctions, bifurcations palaeochannel intersections. Survey, coring excavation reveal persistence mid-channel bars riffles at where channels crossed fills. In common with most other European lowland this evolves later both climate catchment changes major hydrological critical mid-Holocene (c. 5300 BP). However, case Culm, increase fine supply often seen catchments Middle-Late Holocene, occurred later, was insufficient convert single medium-low sinuosity channel-floodplain. allowed heterogeneity biodiversity (including riffle beetles) as part multiple-scales non-uniformity. Indeed pool-riffle is system’s non-uniformity, being due, least part, effects previous history. paper why river survived multichannel state, implication, others did not. These results used bespoke eco-heritage management but could also inform restoration former multi-channel systems worldwide.