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Hydrologic control on proglacial suspended sediment dynamics Richards, George

Abstract

Measuring suspended sediment concentration (SSC) is both costly and labour intensive. Temporal records of SSC are, however, of paramount importance in elucidating issues relating to geomorphology, ecology and water quality. Rating curves, that relate SSC and discharge by a simple linear regression function, are frequently employed by workers to address the problems of recording SSC. Such functions, however, rarely account for more than 50% of the variability in observed SSC. The aim of this thesis is to formulate subseasonal predictive SSC models and to investigate hydrologic controls on proglacial suspended sediment dynamics using data collected from a glacier-fed stream, Coast Mountains, British Columbia. In order to model proglacial SSC, the hydrologic season was initially divided into nival, nival-glacial, glacial and autumn recession periods, according to sudden shifts in the ratio of stream discharge between the glacierised and a neighbouring unglacierised catchment of similar size and aspect. Multiple regression functions, to predict SSC, were then developed for each period. These regression models incorporate a suite of easily measured variables and are shown to reduce significantly, initial problems of autocorrelation, heteroskedasticity and non-linearity of the SSC-discharge relationship. Analysis of the significant parameters in the multiple regression models, the hysteretic relationship between SSC and discharge, and downstream changes in SSC reveal that short-term, within channel, storage of fine sediment may be an important control on proglacial suspended sediment dynamics in this complex glaciofluvial lacustrine system.

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