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.