Reconstructing a 1000 Year High Resolution Flood Record Using a Combined Sedimentary and Modelling Approach

Long term flood records provide essential context for contemporary river flows and flood events, especially given the relatively short period of direct observation for most systems. The sediment deposits in lacustrine deltas offer a potential record of the upstream catchment palaeo-hydrological conditions and associated environmental controls. Herein we collected a 1000 year high resolution ( 0.004 m per year) flood record from a lake (Loch Insh) in the Scottish Highlands, draining a watershed of 750 km2 through the River Spey. Particle size characteristics of flood laminations were correlated with recent (1950 onwards) recorded river flows from the Spey to link the sediment palaeoflood series to river discharges, providing a high resolution proxy record for 1000 years. Additional analyses (ITRAX geochemical, pollen and chironomids) were also undertaken to help constrain the environmental responses and key climatological variations affecting the catchment. We use the HydroTrend model to explore formative river discharges which result in plausible scenarios of sediment delivery to retrodict catchment scale palaeoehydrological change, showing how the approach can be used to establish a long term record of flood frequency and magnitude.