Integrating historical, geomorphological and sedimentological insights to reconstruct past floods: Insights from Kea Point, Mt. Cook Village, Aotearoa New Zealand

Abstract

Flood reconstruction is essential for establishing magnitude-frequency relationships and assessments of contemporary geohazards and risks. Traditionally, flood reconstructions rely upon the analysis of evidence acquired from a single discipline. This lack of integration limits the insights into a flood's source, pathway, and receptors (i.e. impacts). Here, our aim is to test the integration of qualitative historical documentary material with quantitative geomorphological and sedimentological evidence to reconstruct glacial lake outburst floods (GLOFs) in 1913 at Kea Point, Mount Cook National Park, Aotearoa New Zealand. Written documentary records show that, following heavy rainfall, GLOF events occurred in January and March, after the temporary impoundment of water between the glacier surface and lateral moraine. Peak flood discharge was estimated from slope-area and exposed boulder measurements as 316–1077 m3s−1 and 496–1622 m3s−1 respectively. Sedimentological information, combined with geomorphic mapping, a DEM derived from Structure from Motion (SfM) photogrammetry, and satellite imagery was used to describe the overall physical impact of the GLOF. Information from written documentary records, however, enabled a more detailed reconstruction of the timeline of the two floods and their impacts proximate to the original ‘Hermitage Hotel’, which was subsequently relocated. Our integrated approach exemplifies the informative level of multi-faceted detail that can be retrieved for historical flood events. We propose a framework for future studies that seek to reconstruct flood events and their source, pathway and receptors through combining evidence from historical documents/artefacts, sedimentological/geomorphological data, and integration with environmental monitoring/modelling outputs.