View article

Current assessment of flood risk in New Zealand is compromised by short instrumental flow records (less than 50 yr) in most large river catchments. These typically do not include the largest floods that have occurred in the past and which would cause the most damage to life, property and infrastructure.This paper reports the first Late Holocene palaeoflood reconstruction in the North Island of New Zealand within the Manawatu river (c.5950 km2), based on a coring campaign to examine the sedimentary infill of oxbow lakes ('lagoons') in the lower part of the catchment. Study reaches are fully alluvial, with anextensive suite of infilled palaeochannels developed on a series of low elevation cut-terraces and on very low-gradient fluvial plains. The geochemical proxies for the grain-size of individual flood units, recovered by percussion and piston coring, were compared with modelled overtopping discharges for each study …