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Glacial lake outburst floods have produced a distinctive and widespread Quaternary record both onshore and offshore via widespread and intense geomorphological impacts, yet these impacts remain poorly understood due to a lack of modern analogues. This study therefore makes a systematic quantification of the evolution of a bedrock-channelled outburst flood. Channel topography was obtained from digitised aerial photographs, a 5 m grid resolution DEM and bathymetric surveys. Flood inundation was measured in the field from dGPS measurements. Flood evolution was analysed with application of a numerical model. Novel flood metrics, including ‘rate-of-rise-to-peak’ and ‘persistence-above-a-value’ of hydraulics were calculated. The key findings were that outburst floods; (i) that enter intermediary lakes are dramatically attenuated in terms of propagation whilst basin filling proceeds to the outlet level …