GEOMORPHIC MAPPING AND ANALYSIS OF GLACIAL LANDFORMS TO UNDERSTAND THE DEVELOPMENT AND DEFINING CHARACTERISTICS OF ‘GLACIAL’ LAKE SPEIGHT IN THE MIDDLE WAIMAKARIRI RIVER OF THE SOUTHERN ALPS, NEW ZEALAND
Using morphometric observations and images from the field, grain size curves of sediment samples, and orthorectified imagery utilized in ArcGIS, this study provides a detailed geomorphological map of the Middle Waimakariri. This map utilizes field mapping techniques as a tool to understand the timing of landform development, reassessing proposed mechanisms of damming and draining established for ‘glacial’ Lake Speight in the literature, and patterns of paleo-lake ridges. This study concludes that ‘glacial’ Lake Speight was not glacial in origin, but rather a mass-movement dam created shortly after the glacier receded from the terminal moraine region, following a period of alluvial accumulation. The slow pace of drainage deduced from the sequence of multiple paleo-shorelines is explained by the stability of underlying bedrockpre-existing sediment. This drainage pattern and mass movement dam stability have important implications for mass-movement dams as global warming and increasing glacial melting create an increased need for proglacial lake geohazards assessments.