Sediment source partitioning and budgeting over historical timescales in a glacierized, mountain catchment

Abstract

Managing and living with geohazards is especially challenging in mountain landscapes. Informed management relies on an understanding of catchment-scale sediment dynamics and system functioning. Sediment budgeting can be used as a framework and practical management tool to organize and analyze the necessary data. However, it can be challenging to constrain sediment budget components, partition sediment yield measurements by source and grain size, and resolve scale issues. In this study, we seek to better constrain the spatial and temporal patterns of bed material transfer by leveraging a suite of techniques to measure and quantify sediment transfers in a glacierized, mountain catchment. First, we quantify the historical bed material yield using field surveys and historical air photo analysis. Second, we utilize high-resolution, multi-temporal lidar data and detailed geomorphic mapping to construct a detailed sediment budget. A mixed-methods approach and careful uncertainty analysis was required to resolve the historical sediment yield and detailed sediment budgeting results. In the Fitzsimmons Creek Watershed, the annual sediment yield varied by up to a factor of 10 over the 76-year record. Sediment source partitioning suggests landslides, active channel, and floodplain sources each contributed 1/3 of the total sediment supply. Importantly, the landsliding occurs proximal to the outlet and transports glacial valley fill to the channel, significantly increasing sediment yield. Point-based sediment yield estimates are helpful for long-term evaluation of landscape denudation and system change, while detailed sediment budgets provide information necessary for understanding complex system functions and dynamics, and for management applications.